By comparison with the commonly seen visible light images that can be effectively characterized within a Euclidean space, infrared images have non-Euclidean characteristics since their pixels contain rich thermal radiation information, such as heat distribution, surface temperature and thermal radiation. Considering the advantages of Graph Convolutional Networks (GCNs) in processing non-Euclidean data, this study proposes to introduce the GCNs to estimate the quality of infrared images by developing the Node-to-Graph Regression (NGR) model. To specify, the proposed NGR model is composed of two main steps, namely network establishment and network training. In the first step, following the classical researches of image quality estimation that include local distortion measurement followed by pooling for inferring the image quality score, this study captures the local distortion of the input infrared images by stacking up a set of Vision Graph (VSG) blocks to generate one node map, and then conducts the weighted pooling method on the node map to yield the graph output as the estimated quality score. In the second step, for enhancing the model's performance and generalization ability in the network training process, this study implements the node regression with the big data pre-training method to raise the local distortion extraction ability in a broad range of image scenarios and distortion intensities, and then performs the graph regression by using the knowledge distillation method to reduce the over-fitting risk. Using the largest-size infrared image quality evaluation database (I2QED), this study compared the proposed NGR model with three dozen mainstream and state-of-the-art competitors, and results showed that our proposed NGR model achieved the optimal performance.

This special issue is the third issue dedicated to the best papers of the second Call of the CGI 2022 conference. In 2022, CGI (Computer Graphics International) was organized by MIRALab at the University of Geneva. It was supported by the Computer Graphics Society. The conference was very successful and attracted more than 150 online participants through Zoom. Twenty-six papers were selected from more than 100 papers submitted to the second call of the conference. This issue contains the last eight full papers. Nine papers were already published in the 33.5 issue and nine papers in the 33.6 issue. All papers have been reviewed by two or three reviewers of the CGI 2022 Program Committee, revised according to the reviewers' comments, and checked and reviewed again by the CAVW Editorial Board. Data-driven based double-layer bicycle simulation model by Tianlu Mao, Zhong Fang, Qinyuan Yan, and Zhaoqi Wang, from Academy of Sciences, Beijing, and Ruoyu Meng and Shaohua Liu, all in China. This special issue is edited by the program-co-chairs of CGI2022 conference.

This issue contains 10 papers. In the first paper, Diego Mazala and Claudio Esperança, from Universidade Federal do Rio de Janeiro in Brazil, and Ricardo Marroquim, from Delft University of Technology in Netherlands, present a novel method for blending human faces in order to create a new one. In a nutshell, their proposal uses Laplacian smoothing to segregate layers of details from one or more faces, which are then integrated into a base face with the help of an interactive and visual editor. In particular, their method supports blending multiple faces and multiple subregions in those faces. Since their approach is intuitive and relatively easy to implement, it can be integrated into artistic pipelines aiming at designing human face models from preexisting ones. In the second paper, Ulas Gulec, from TED University Ankara, Turkey, Ilkin Sevgi Isler, from University of Central Florida in Orlando, USA, Mehmet Harun Doganay and Muruvet Gokcen, from Milsoft Software Technologies, in Ankara, Turkey, Mert Ali Gozcu, from Simsoft Information Technologies in Ankara, Turkey, and Merve Denizci Nazligul, from Yeditepe University in Istanbul, Turkey, propose a study that aims to increase the motivation levels of powerlifters during training sessions by developing a virtual competition environment. In this environment, the athletes experience a virtual competition environment by using HTC Vive. To understand the efficiency of the virtual environment, it was tested with 32 professional athletes. The findings illustrated that using VR technology was beneficial to increase the level of motivation of powerlifters during training sessions. In the third paper, Jinyu Li, Xin Zhou, Bangbang Yang, Guofeng Zhang, Xun Wang, and Hujun Bao, from Zhejiang University in Hangzhou, China, propose RLP-VIO—a robust and lightweight monocular visual-inertial odometry system using multiplane priors. With planes extracted from the point cloud, visual-inertial-plane PnP uses the plane information for fast localization. For sensor fusion, their sliding-window optimization uses a novel structureless plane-distance error cost, which prevents the fill-in effect that poisons the BA problem's sparsity and permits the use of a smaller sliding window while maintaining good accuracy. The total computational cost is further reduced with their modified marginalization strategy. To further improve the tracking robustness, the landmark depths are constrained using the planes during degenerated motion. The whole system is parallelized with a three-stage pipeline. Their system achieves competitive accuracy and works robustly even on long and challenging sequences. In the fourth paper, Ruizhe Li, Ryo Oji, and Issei Fujishiro, from Keio University in Yokohama, Japan, present an anime-like character customization system, where each customizing parameter can adjust the shape or color for the corresponding part of the character model. Based on this system, the authors propose an improved approach for generating a rich variety of 3D anime-like NPCs including body models and clothing items in different styles. They introduce a neural network to control the facial appearances, Gaussian mixture models to control the colors of hair and clothes, and a Bayesian network to control the outfits of clothing items. They demonstrate the proposed approach can maintain variety and stability for generated characters. The fifth paper by Cheng Shang, Hongke Zhao, Meili Wang, Xiao Long Wang, Yu Jiang, and Qiang Gao, from Northwest Agriculture and Forestry University in Yangling, China, focuses on the identification of cashmere goats with similar characteristics. First, the single shot detection network was used to process the data set. Next, the authors innovatively proposed the multibranch fusion optimization structure of triplet loss function and Label Smoothing CrossEntropy Loss function, as well as they added a small number of images of 24 different breeds of sheep to each cashmere goat dataset with different ID to promote the distance between training individuals, and then used the trained model to find the number of goats with the lowest recognition accuracy. Unlike previous studies using the Cycle-GAN, the authors took the novel approach of using this network to learn and combine the features seen in photos of cashmere goats. Since the learned features were all observed in the same goats, this method achieved better results in learning the features of the goats. In the sixth paper, Jia Chen, Haidongqing Yuan, Yi Zhang, Ruhan He, and Jinxing Liang, from Wuhan Textile University in China, propose a fashion image retrieval framework based on dilated convolutional residual network that consists of two major parts, image feature extraction and feature distance measurement. For image feature extraction, they first extract the shallow features of the input image by a multiscale convolutional network, and then develop a novel dilated convolutional residual network to obtain the deep features of the image. Finally, the extracted features are transformed into high-dimensional features vector by a binary retrieval vector module. For feature distance measurement, the authors first use PCA to reduce the dimension of the extracted high-dimensional vectors. Then they propose a mixed distance measurement algorithm combined with cosine distance and Mahalanobis distance to calculate the spatial distance of the feature vectors for similarity ranking. In the seventh paper, Yi-Jheng Huang, from Yuan Ze University in Taoyuan, Taiwan, proposes an algorithm for detecting edges based on the color of a mesh surface. His approach is based on the data structure of a quad mesh, which makes the data structure of 3D meshes resemble the data structure of images. As a result, image-processing methods can be applied on the 3D meshes. In this paper, six classical edge detection filters are implemented on the 3D meshes. The experimental results demonstrate that his method can identify areas of high color gradient on 3D meshes. A comparison with two other methods for detecting color boundaries on 3D meshes reveals that his method is more effective at detecting boundaries. Lastly, he proposes two novel applications that utilize the information of color boundaries on a 3D mesh surface. In the eighth paper, Xue Du, Juan Xiu Sun, Kunpeng Wang, Junlong Yang, and Jiang Chuan Wang, from Shandong University of Science and Technology in China, propose an underwater image enhancement method based on entropy weight fusion for underwater images. First, white balance processing can effectively correct the blue (green) color appearance of the image. Then the white-balanced images are converted from RGB space to LAB space, and L channel is processed with improved adaptive gamma correction, and then converted back to RGB space. CLAHE and bilateral filtering are performed in RGB space. The RGB space is converted to HSV space, the V channel is processed by single-scale Retinex algorithm combined with guided filtering, stretching the R channel with s-cosine curve, and then converted back to RGB space. Finally, the three results are fused by entropy weight to obtain the final enhanced image. Experimental results show that the proposed algorithm can improve the contrast and clarity of underwater images, and effectively remove color cast. In the ninth paper, Ana Agić, Lidija Mandić, and Lea Skorin-Kapov, from University of Zagreb in Croatia, report on the results of a user study aimed to investigate and compare three types of locomotion techniques in VR in terms of their impact on cybersickness. The different locomotion techniques are tested in two different contrast scene settings, daytime and nighttime, to further explore the potential impact of scene contrast adjustments. For the evaluation of cybersickness, the authors used a questionnaire to obtain subjective ratings, and heart rate monitoring as an objective metric. Results show that a linear movement locomotion technique provokes the highest level of cybersickness, and that women have a higher heart rate as compared with men when navigating and interacting in a VR scene. Regarding the influence of scene contrast, results showed that scenes with daylight were better suited to participants in almost all tested scenarios. In addition to reported findings related to locomotion techniques and the impact on cybersickness, they highlight that a key contribution is the utilized test methodology. The last paper by Zafar Masood, Jiangbin Zheng, Muhammad Irfan, and Idrees Ahmad, from Northwestern Polytechnical University in Xi'an, China, presents a novel method for a high-performance large-scale terrain rendering for high-fidelity display systems using game engine. The proposed method performs patch-based hierarchical culling of a multiresolution terrain model to reduce rendering load. A view-based algorithm simplifies the patches with error control on GPU. Simplified patches are efficiently submitted for drawing using indirect mesh instancing feature of game engine. The method utilizes hardware tessellation feature for high-performance model tessellation and accurate Earth's surface construction using displacement mapping. The proposed method is evaluated by rendering scenes for high-quality output on consumer-level hardware. Flights are performed with various settings and results are compared with clipmap-based and state-of-the-art hardware tessellation based adaptive methods. The method achieved 750, 575, and 540 frames-per-second (fps) for HD, full-HD, and ultra-HD display resolutions.

VRLAB

This issue contains 12 regular papers. In the first paper, Hong Li et al. present an animation translation method based on edge enhancement and coordinate attention, which is called FAEC-GAN. They design a novel edge discrimination network to identify the edge features of images, so that the generated anime images can present clear and coherent lines. And the coordinate attention module is introduced in the encoder to adapt the model to the geometric changes in translation, to produce more realistic animation images. In addition, the method combines the focal frequency loss and pixel loss, which can pay attention to both the frequency domain information and pixel information of the generated image to improve the visual effect of the image. In the second paper, Rahul Jain et al. propose an algorithm to convert a depth video into a single dynamic image known as a linked motion image (LMI). The LMI has been given to a classifier consisting of an ensemble of three modified pre-trained convolutional neural networks (CNNs). The experiments were conducted using two datasets: a multimodal large-scale EgoGesture dataset and The MSR Gesture 3D dataset. For the EgoGesture dataset, the proposed method achieved an accuracy of 92.91%, which is better than the state-of-the-art methods. For the MSR Gesture 3D dataset, the proposed method accuracy is 100%, which outperforms the state-of-the-art methods. The recognition accuracy and precision of each gesture are also highlighted in this work. In the third paper, Rustam Akhunov et al. propose a set of experiments to aid the evaluation of the main categories of fluid-boundary interactions that are important in computer animation, i.e. no motion (resting) fluid, tangential and normal motion of a fluid with respect to the boundary, and a fluid impacting a corner. They propose 10 experiments, comprising experimental setup and quantitative evaluation with optional visual inspections, that are arranged in four groups which focus on one of the main category of fluid-boundary interactions. The authors use these experiments to evaluate three particle-based boundary handling methods, that is, Pressure Mirroring (PM), Pressure Boundaries (PB) and Moving Least Squares Pressure Extrapolation (MLS), in combination with two incompressible SPH fluid simulation methods, namely IISPH and DFSPH. In the fourth paper, Shenghuan Zhao et al. present three Extended Reality (XR) apps (AR, MR, and VR) to interactively visualize façade fenestration geometries and indoor illuminance simulations. Then XR technologies are assessed by 120 students and young architects, from task performance and engagement level two aspects. The task performance is measured by correct rate and time consumption two indicators, while the engagement level is measured by usability and interest two indicators. Evaluation results show that compared to AR and VR, MR is the best XR technology for this aim. VR outperforms AR on three indicators except for usability. By exposing three different XR technologies' performances in aiding fenestration design, this study increases the practical value of applying XR to the building design field. The fifth paper by Jing Zhao et al. focuses on a multiple-fluid coupling simulation algorithm based on MPM and PFM. First, based on the MPM, they model multiphase flow on Eulerian grids and capture the sharp interfaces between immiscible fluids combined with the PFM. The gas phase is further treated as a fluid during the gas–liquid interaction. Second, to demonstrate the natural fluid moving evolution from the high energy state to the low energy state, the paper proposes the local minimize bulk energy function to control the low energy state. Finally, the paper designs and achieves various groups of multiple-fluid coupling comparison experiments. Experimental results showed that the proposed approach can simulate various effects of rapid diffusion in the multiple-fluid coupling, such as complete dissolution, mutual solubility, extraction, and other phenomena. In the sixth paper, Jiwei Zhang et al. propose a novel method fusing multiple heterogeneous features through a multi-feature subspace representation network (MFSRN) to maximize the classification performance while keeping the disparity among features as small as possible, that is, common-subspace constraints. The authors conducted comparative experiments with state-of-the-art models on the bird's-eye view person dataset, and extensive experimental results demonstrated that the proposed MFSRN could achieve better recognition performance. Furthermore, the validity and stability of the method are confirmed. In the seventh paper, Sahadeb Shit et al. propose a convolutional neural network (CNN)-based image dehazing and detection approach, called End to End Dehaze and Detection Network (EDD-N), for proper image visualization and detection. This network is trained on real-time hazy images that are directly used to recover dehaze images without a transmission map. EDD-N is robust, and accuracy is higher than any other proposed model. The authors also conducted extensive experiments using real-time foggy images. The quantitative and qualitative evaluations of the hazy dataset verify the proposed method's superiority over other dehazing methods. Moreover, the proposed method validated real-time object detection tasks in adverse weather conditions and improved the intelligent transportation system. In the eighth paper, Chaehan So et al. designed a virtual being from a deep learning-generated face and a conversational AI model acting as a virtual conversation partner in an online conferencing software and evaluated it in 11 perceptions of social attributes. Compared to prior expectations, participants perceived the virtual being as distinctly higher in warmth (engaging, empathic, and approachable) but lower in realism and credibility after 5 days of 10-min daily conversations (Study 1). Further, the authors explored the idea of simplifying the technical setup to reduce the technical entry barrier for such experiments (Study 2). To this aim, they conducted several trials of fine-tuning a small conversational model of 90 million parameters until its performance metrics improved. Testing this fine-tuned model with users revealed that this model was not perceived differently from a large conversational model. In the ninth paper, Di Qi et al. propose a novel split and join approach to simulate a side-to-side stapled intestinal anastomosis in virtual reality. They mimic the intestine model using a new hybrid representation—a grid-linked particles model for physics simulation and a surface mesh for rendering. The proposed split and join operations handle the updates of both the grid-linked particles model and the surface mesh during the anastomosis procedure. The simulation results demonstrate the feasibility of the proposed approach in simulating intestine models and the side-to-side anastomosis operation. The tenth paper by Lanfeng Zhou et al. present a novel graph convolution mixed with point cloud deep learning method. In this method, the skinned multi-person linear model is regarded as a graph structure input, and the coarsened graph is obtained by graph convolution. After feeding the coarsened graph into the PointNet network, the coordinates of Dazhui are output. Different from the existing methods, the proposed method can directly label the results on the adaptive model, thus improving the accuracy on different models. An optimization method based on graph structure is introduced for better fit the predicted acupoints to the surface. In addition, a dataset marked with Dazhui is constructed for training. Experiments show that the accuracy of positioning could meet the requirements of needle application under certain circumstances. In the eleventh paper, Jian Lu et al. propose to reduce the interference of the factors in skeleton-based action recognition, by taking the joint coordinate modal information of 2D skeleton to represent the change of human posture as the research point: first, the joint coordinates are obtained from RGB video or image using a detector. Then the feature extraction network is combined to perform multi-level feature learning to establish correspondence between actions and corresponding multi-level features. Finally, the hierarchical attention mechanism is introduced to design the CHAN model. By calculating the association between elements, the weight of the action classification is redistributed. The proposed method has good performance on UT-Kinect, KTH and NTU RGB + D datasets. The last paper by Numan Ali et al. first conducted a subjective study with field experts to investigate about the practical implementation of their existing virtual chemistry laboratory (VCL). To consider the suggestions of the field experts, they propose task specific aids based virtual reality chemistry laboratory (TSA-VRCL) to minimize students' cognitive load and enhance their performance. The task specific aids consist of an arrow, animation and audio aids that are separately rendered with each step of the experimental tasks. During evaluations, 80 students performed the experiments in four different groups using four different experimental conditions. Evaluations revealed that the proposed TSA-VRCL minimizes students' cognitive load and enhances their performance. Professor Magnenat Thalmann started her career in Canada at the University of Montreal where she pioneered the field of 3D Virtual Humans. In 1989, she created the laboratory MIRALab at the University of Geneva, a ground-breaking research lab developing Virtual Humans and Social Robots. From 2019 to 2022, she was the Director of the research Center Being there and the Research Institute IMI in Nanyang Technological University (NTU) in Singapore. In NTU, Singapore, she revolutionized social robotics by unveiling the first social robot Nadine that can show mood and emotions and remember people and actions. Besides having bachelor's and master's degrees in disciplines such as psychology, biology, chemistry and computer science, Professor Thalmann completed her PhD in quantum physics at the University of Geneva. She has received honorary doctorates from Leibniz University of Hannover and the University of Ottawa in Canada and several prestigious other Awards as the Humboldt Research Award in Germany, the Eurographics Career Award and the Canadian Human Computer Communications Society Award. She is a life Member of the Swiss Academy of Engineering Sciences. For more information about her academic achievements, see google scholar. Prof. Daniel Thalmann is a Swiss and Canadian computer scientist. He is currently an honorary professor at the EPFL in Switzerland and the executive director of R&D at MIRALab Sarl. He is co-editor-in-chief of Wiley's Journal of Computer Animation and Virtual Worlds (CAVW) and on the editorial boards of several other journals. Daniel Thalmann is programme chair and co-chair of CASA2023 and CGI2023. After receiving his Ph.D. in Computer Science from the University of Geneva in 1977, Daniel Thalmann began at the University of Montreal in Canada. He later became a professor at EPFL, Switzerland, where he founded the Virtual Reality Lab (VRlab). From 2009 to 2017, he was a visiting professor at the Nanyang Technological University in Singapore. Throughout his successful career, Professor Daniel Thalmann has received many awards, including an Honorary Doctorate from Paul Sabatier University in Toulouse, France in 2003, the Eurographics Distinguished Career Award in 2010, the Canadian Human Computer Communications Society Achievement Award in 2012, and the CGI Career Achievement Award in 2015. More can be found on Daniel Thalmannin Wikipedia.

This special issue is dedicated to the best papers of the second Call of the CGI 2022 conference. This year CGI (Computer Graphics International) was organized by MIRALab at the University of Geneva. It was supported by the Computer Graphics Society. The conference was very successful and attracted more than 150 online participants through Zoom. Twenty-six papers were selected from more than 100 papers submitted to the second call of the conference. This issue contains nine full papers. The other selected papers will be published in the two next issues respectively 33.6 and 34.1. All papers have been reviewed by two or three reviewers of the CGI 2022 Program Committee, revised according to the reviewers' comments, and checked and reviewed again by the CAVW Editorial Board. The first paper in this issue is the recipient of the CAVW Best Paper Award given at CGI 2022 by the Award Committee chaired by Professor Nadia Magnenat Thalmann, MIRALab-University of Geneva, Switzerland, and Professor Constantine Stephanidis, ICS—FORTH, Greece. This awarded paper is: Simulation of collective pursuit-evasion behavior with runtime situational awareness by Zhenjing Yu, Tan Junyin, and Sheng Li, from Peking University, China.

This special issue is the second issue dedicated to the best papers of the second Call of the CGI 2022 conference. This year CGI (Computer Graphics International) was organized by MIRALab at the University of Geneva. It was supported by the Computer Graphics Society. The conference was very successful and attracted more than 150 online participants through Zoom. Twenty-six papers were selected from more than 100 papers submitted to the second call of the conference. This issue contains nine full papers. Nine papers were already published in the 33.5 issue and the last papers will appear in the issue 34.1. All papers have been reviewed by two or three reviewers of the CGI 2022 Program Committee, revised according to the reviewers' comments, and checked and reviewed again by the CAVW Editorial Board. This special issue is edited by the program co-chairs of CGI2022 conference: Jinman Kim, Sydney University, Australia, George Papagiannakis, University of Crete, Greece, Bin Sheng, Shanghai Jiao Tong University, China, Daniel Thalmann, EPFL, Switzerland.

This issue contains five papers. In the first paper, Yuling Yan, Lijun Zhang, from Suzhou University, China and Minye Chen, from Shanghai University of Science and Technology, all in China propose a virtual training system of aircraft maintenance based on gesture recognition interaction. Leap Motion is used as a sensor to construct a hybrid machine learning gesture recognition model, to obtain natural human–computer interaction experience. In the recognition model, the initial weight matrix, and the number of hidden layer nodes in the BPNN are jointly optimized by the PSO algorithm with self-adaption inertial weight. This optimization algorithm achieved a recognition rate of 81.26% in the dynamic gesture database constructed in this paper, which is higher than other available algorithms. A preliminary usability evaluation in university classrooms shows that the teaching system in this paper can achieve a better interactive experience. In the second paper, Junsong Zhang, Zhu Shaoqiang, Kunxiang Liu, and Xiaoyu Liu, from National Engineering Research Center for E-learning, in Wuhan, China, propose a novel adversarial architecture for multiple sketch colorization which is a scribble-based, automatic and exemplar-based colorization method. The proposed framework has two stages, namely imitating stage, and shading stage. In the imitating stage, to address the challenge of lack of texture in the sketch, the authors train a grayscale generation network to accomplish a mapping task, namely generating a grayscale map with textured, grayscale, boundary information from the input sparse sketch. In the shading stage, the model can accurately colorize the objects in the gray image generated in the previous stage and generate high-quality colorized images. With the proposed model trained on their database, the experimental results show that their method can generate vivid colorized images and achieve a better performance than previous methods evaluated by FID metric. In the third paper, Assia MESSACI, Zenati Nadia, Belhocine Mahmoud, from CDTA, Algiers, Algeria and Otmane Samir, from Université Evry, Université Paris-Saclay, France propose the Zoom-fwd, which is an efficient 3D interaction technique. The proposed technique uses gesture recognition for different 3D interaction tasks like selection and manipulation. This new approach allows an efficient interaction with distant and occluded objects, while providing a precise selection, even when the environment is crowded. A user study is conducted to determine whether the proposed technique is more suitable when performing interaction tasks. The results show that the Zoom-fwd technique provides effective interaction with distant and occluded objects. The fourth paper, by Wen Zhou, Wenying Jiang, Biao Jie, and Weixin Bian, from Anhui Normal University, in Wuhu, China, present a multiagent evacuation framework for complex virtual fire scenarios, effectively used to simulate the procedure of multiagent evacuation to approximate the goal of fire drills in a least-cost manner. Specifically, the concept of a multihierarchy agent group model is proposed; that is, the evacuation of multiple agents is separated into leader-follower and freedom modes. Additionally, several complex actions of individual humans in actual fire drills are fully considered, and a multiaction agent schema is presented to characterize the associated real effects. In addition, generative adversarial imitation learning (GAIL) is adopted to obtain the evacuation path of the leader-agent by training numerous learning epochs. The results of extensive experiments show that the proposed method is feasible and realistically and reasonably shows the procedure of multiagent evacuation in complex fire emergency scenarios. The last paper by Jingjing Zhang, Jingsheng Lei, Shengying Yang, and Xinqi Yang, from Zhejiang University of Science and Technology, in Hangzhou, China propose the SIL-Net designed to discover semantic differences between two fine-grained categories via pairwise comparison. Specifically, SIL-Net first collecting contrastive information by learning the mutual feature of input image pair, and then compare it with individual features to generate corresponding semantic features. These features learn semantic differences from contextual comparison, this gives SIL-Net the ability to distinguish between two confusing images via pairwise interaction. After training, SIL-Net can adaptively learn feature priorities under the supervision of the margin ranking loss and converge quickly. SIL-Net performs well on two public vehicle benchmarks (Stanford Cars and CompCars), showing the suitability of SIL-Net to fine-grained vehicle recognition.

This issue contains five papers. In the first paper, Ege Tekgün, Muhtar Çağkan Uludağlı, Hüseyin Akcan, and Burak Erdeniz, from Izmir University of Economics in Turkey assess the influence of virtual avatar anthropomorphism and the synchronicity of the visuo-tactile stimulation on self-location using a virtual reality (VR) full-body illusion (FBI) experiment. During the experiment, half of the 36 participants observed a gender-matched full-body humanoid avatar from a first-person perspective (1PP) and the other half observed a less anthropomorphic full-body cubical avatar from 1PP while they were receiving synchronous and asynchronous visuo-tactile stimulation. Results show a significant main effect of the synchronicity of the visuo-tactile stimulation and avatar body type on self-location but no significant interaction was found between them. Moreover, the results of the self-report questionnaire provide additional evidence showing that participants who received synchronous visuo-tactile stimulation, experienced not only greater changes in the feeling of self-location, but also, increased ownership, and referral of touch. In the second paper, Ke Li, Qian Zhang, Jinyuan Jia, from Tongji University in Shanghai, China, and Hantao Zhao, from Southeast University in Nanjing, all in China discuss the technology of presenting building information modeling (BIM) with an online platform and the difficulty to display large-scale BIM scenes in a flawless manner on mobile browsers, due to network bandwidth and browser performance limitations. The authors propose CEBOW, a Cloud-Edge-Browser Online architecture for visualizing BIM components with online solutions. The method combines transmission scheduling, cache management, and optimal initial loading into a single system architecture. For network transmission testing, BIM scenes are used, and the results show that their method effectively reduces scene loading time and networking delay while improving the visualization effect of large-scale scenes. In the third paper, Yuzhu Dong and Eakta Jain, from University of Florida in Gainesville, and Sophie Jörg, from Clemson University, all in United States discuss how the importance of eyes for virtual characters stems from the intrinsic social cues. They emphasize that the eye animation impacts the perception of an avatar's internal emotional state. They present three large scale experiments that investigate the extent to which viewers can identify if an avatar is scared. The authors find that participants can identify a scared avatar with 75% accuracy using cues in the eyes including pupil size variation, gaze, and blinks. Because eye trackers return pupil diameter in addition to gaze, their experiments inform practitioners that animating the pupil correctly will add expressiveness to a virtual avatar with negligible additional cost. These findings also have implications for creating expressive eyes in intelligent conversational agents and social robots. The fourth paper, by Osman Güler, from TUSAŞ Şehit Hakan Gülşen Vocational and Technical Anatolian High School in Ankara and Serkan Savaş, from Çankırı Karatekin Üniversitesi, both in Turkey present a study showing that Interactive Boards (IBs) have the necessary hardware to run Stereoscopic 3D (S3D) training materials, but the panel has not got an S3D imaging feature. Therefore, only the Anaglyph S3D imaging method can be applied to IBs. Thus, an Anaglyph S3D training material was prepared for the interaction of the skeletal system and interactive 3D material design for IBs with its effects in education was investigated. A Likert-type scale was developed to measure the usability of the training material on IBs and the material was evaluated by 20 experts. The data were analyzed by the SPSS statistical program and the results were interpreted. According to the results, educational material seems to be positive in terms of image characteristics, content, navigation, and ease of use, font sizes were moderate for readability, the feedback process and the help menu were moderately effective. The last paper by Alexandra Sierra, Marie Postma, from Tilburg University in Netherlands and Menno Van Zaanen, from North-West University in Potchefstroom, South Africa investigate whether the uncanny valley effect, which has already been found for the human-like appearance of virtual characters, can also be found for animal-like appearances. They conducted an online study in which six different animal designs were evaluated in terms of the following properties: familiarity, commonality, naturalness, attractiveness, interestingness, and animateness. The study participants differed in age (under 10–60 years) and origin (Europe, Asia, North America, and South America). For the evaluation of the results, the authors ranked the animal-likeness of the character using both expert opinion and participant judgments. They also investigated the effect of movement and morbidity. The results confirm the existence of the uncanny valley effect for virtual animals, especially with respect to familiarity and commonality, for both still and moving images. No uncanny valley effect was detected for interestingness and animateness.

CGI is one of the oldest international conferences in Computer Graphics in the world.It is the official conference of the Computer Graphics Society (CGS), a long-standing international computer graphics organization.CGI conference has been held annually in many different countries across the world and has gained a reputation as one of the key conferences for researchers and practitioners to share their achievements and discover the latest advances in Computer Graphics.With the change in the form of networking and intelligence in industry, manufacturing and all aspects of society, and the development of technology, we are aware of the increasingly obvious trend of evolution of intelligence in human society.Among them, metaverse is increasingly becoming a hot spot for research in various industries and has broad application prospects.It absorbs the results of the information revolution, the Internet revolution, the artificial intelligence revolution, and the virtual reality technology revolution including VR, AR, MR, and especially game engines, showing mankind the possibility of building a holographic digital world parallel to the traditional physical world.The core of the metaverse lies in the hosting of virtual assets and virtual identities.Unlike traditional games, users can experience different content, make different friends, create their own creations, and perform a series of virtual activities in the metaverse.With the popularity of smart terminals and the rise of applications such as e-commerce/short videos/games, "metaverse" has become an inevitable trend in the development of digital society.In a broad sense, the "metaverse" is a virtual space-time consisting of a series of augmented reality (AR), virtual reality (VR) and the Internet; in a narrow sense, the "metaverse" is a virtual world parallel to the real world.By wearing a helmet and headset device, one can enter a three-dimensional world constructed by computer simulation through a terminal connection".The new mode of "virtual reality" presentation and scene interaction for scene visualization will be more conducive to better visual effects and interactive operations in the digital world.The metaverse becomes the best track and new growth point for AI applications because of its huge imagination, close social attention and rich landing scenes, while AI and related arithmetic, big data and other technical fields are the technical base for the metaverse to become a kind of concrete expression in the future.Overall, with the further development of human technology and the improvement of hardware level, it becomes possible for humans to build a "meta" world.This year, CGI 2022 is still online as the pandemic prevents many researchers to come to Geneva.The conference CGI is organized from September 12 to September 16, 2022, by MIRALab at the Computer Research Centre (CUI) of the University of Geneva, in Switzerland.All presentations are online.In addition to the Visual Computer journal published by Springer, and the CAVW journal (Computer Animation and Virtual Worlds) published by Wiley, we have also included the twenty-three accepted papers in the VRIH journal (Virtual Reality and Intelligent Hardware journal published by Science Press).This special issue is composed of the six papers related to the topic of metaverse from these twenty-three accepted papers.

This special issue contains 24 full papers selected from the Computer Animation and Social Agents 2021 Conference (CASA2021). This conference was founded by the Computer Graphics Society (CGS) in 1988 in Geneva and is the oldest conference on Computer Animation in the world. It has been held in many countries around the world and in recent years in Beijing, China (2018), Paris, France (2019), Bournemouth, UK (2020), and this year in Ottawa, Canada. The two last conferences have been organized virtually due to the Covid-19 pandemy.

VRLAB

present a role-based attention model for reinforcement learning.The proposed model uses convolutional neural networks to generate soft attention maps, adding crucial role information in the task, forcing the agent to focus on important features, and distinguish task-related information.To validate the performance in complex problems, the proposed approach is evaluated in a challenging scenario, Football Academy in Google Research Football Environment, a newly released reinforcement learning environment with physics-based 3D simulator.The experimental results demonstrate that agents using role-based attention mechanism can perform better in football games.

This issue contains seven papers. In the first paper, Monan Wang and Jiaqi Cao, from Harbin University of Science and Technology in China have conducted in-depth research on collision detection, especially the collision detection of deformable objects, which is a bottleneck of virtual environment simulation. First, they briefly review the general problem of collision detection and how authors solve it. They then review the popular research methods and limitations of collision detection between deformable objects. Finally, they review the popular research methods and limitations of self-collision detection in deformable objects. They also discuss future directions of development. This review can be used as a reference for the application of collision detection in all directions. In the second paper, Priyadarshi Biplab Kumar, from NIT Hamirpur and Dayal R.Parhi and Mukesh Sethy, from National Institute of Technology Rourkela both in India, propose a firefly based computer vision integrated navigational analysis. It is intended to perform on humanoid robots for smooth movement by negotiation with obstacles present in complicated terrains. Here, the logic of the firefly algorithm has been used to design the controller by careful consideration of the navigational parameters. A computer vision-based method is integrated along with the developed controller. It is used to resolve some conflicting situations that may arise by encountering large sized obstacle or detection of an obstacle exactly in front of the robot where the robot becomes confused regarding the direction of turn. The developed navigational model has been tested in simulation environments using a NAO robot as humanoid platform. The simulation results are also verified through an experimental platform developed under research laboratory conditions. In the third paper, Oguzhan Tastan and Yusuf Sahillioglu, from METU in Ankara, Turkey propose a novel approach for reconstructing plausible 3D human body models from small number of 3D points which represent body parts. They leverage a database of 3D models of humans varying from each other by physical attributes such as age, gender, weight, and height. First, they divide the bodies in database into seven semantic regions. Then, they search the database for the best matching body part. For the matching criterion, they use the distance between novel point-based features of input points and body parts in the database. They then combine the matched parts from different bodies into one body. To evaluate their results objectively, they pick points from each part of the ground-truth human body models, then reconstruct them using their method and compare the resulting bodies with the corresponding ground-truths. The fourth paper, by Jong-Chul Yoon, from Kangwon National University, in Samcheok, and HyeongYeop Kang, from Kyung Hee University, Yongin, both in Korea, present a smartphone AR application, named the AR-E-Helper, which assists the learning of students in higher education lectures. Their goal is to provide an AR enhanced learning experience for students. To validate the effectiveness of the AR-E-Helper, they conducted an experiment that compares three classes: AR enhanced, smartphone enhanced, and non-technology enhanced classes. Through the experiment, they observed that their application was helpful in maintaining student's focus in class, promoting their interest, and increasing their satisfaction. Furthermore, they also found how to improve their application based on the observations that the application brought some downsides to the learning activities. In the fifth paper, Yun Sik Cho, Jie Won Kang, Jaekyung Jeon, Jong Chan Park and Jinmo Kim, from Hansung University, and Mingyu Kim, from Korea University, all in Seoul, Korea present a study in Virtual Reality for education. During this study, the researchers created a virtual environment for use in Southern Africa, where students could practise managing a young adult with a foreign object in the airway. The aim of the virtual environment was to determine whether a viable, “home-made” solution could be created which could also be expanded later to incorporate more scenarios. This was due to the expensive nature of existing systems for virtual clinical simulation. To determine whether the virtual environment is usable, two expert review panels assisted in testing the virtual environment. The first panel being Computer Science experts and the second Health Science experts. Each panel evaluated the environment and the scenario using heuristic evaluation and cognitive walkthroughs. In the sixth paper, Lin Zhuo, Zhen Liu, Tingting Liu, and Yanjie Chai, from Ningbo University and Chih-Chieh Hung, from National Chung Hsing University, Taichung, all in China present simple, highly immersive x-person asymmetric interactions that account for the experience type characteristics of asymmetric virtual environments, jointly experienced by virtual reality (VR) users and augmented reality (AR) users. The first-person interactions for VR users are performed using hand gestures, and they define a manipulation process that maps the gestures and object control scheme to provide intuitive interactions with the virtual environment and objects. The third-person interaction for AR users is designed to view the overall virtual scene and recognize and judge situations to allow for intuitive communication and interactions among the virtual environment, objects, and users based on a touch interface. The core goal of this process is to provide all users who participate in asymmetric virtual environments with satisfying experiences and an improved presence through individualized experience modes and roles. The last paper by Zhiyong Chen, Xiaowei Chen, Shihui Guo, Minghong Liao, from Xiamen University and Yong Ma, from Jiangxi Normal University, in Nanchang, all in China and Yipeng Qin, from Cardiff University, in UK propose a crowd emotional model to simulate the crowd movement in outdoor emergency situations. First, the crowd entropy and the movement difference are proposed to describe the emotional impact of the crowd scene on the agents. The perception of vision and hearing are considered, and the calculation formulas of the agent's emotional intensity and crowd emotional contagion are proposed. By calculating individual trajectories in the real video, the cumulative differences between the movements of the real crowd and the corresponding virtual crowd are analyzed. At last, a multi-parameter optimization method is implemented by the differential evolution algorithm. To verify the parameters in models, three videos which are generated from three real cases, including explosion attack, shooting incident, and crowd disturbance are selected for experimental verification.

This issue contains five papers. In the first paper, Kun Qian from King's College in London, UK, Meili Wang, from Northwest Agriculture and Forestry University, in Shannxi, China and Yaqing Cui, Bournemouth University, in Poole, UK propose a simulation ready model generation pipeline which can convert a non-manifold polygonal surface mesh into a degeneracy free surface while preserving the original model's surface parameterization attribute. Their pipeline includes two stages. The first stage is a voxelization and remesh based simulation ready model generation pipeline which can keep the shape of original 3D surface model meanwhile eliminate the non-manifold geometry. In the second stage, a cutting-based surface mesh parameterization transfer algorithm is proposed which can transfer the original surface parameterization to the simulation ready model. Detailed comparison with existing pipelines shows that the proposed pipeline can achieve surface parameterization preservation feature and is more suitable for improving the efficiency of virtual surgery production. In the second paper, Muhammad Usman and Petros Faloutsos, from York University in Toronto, Canada, Brandon Haworth, from University of Victoria in Canada and Mubbasir Kapadia, from Rutgers University, Piscataway in USA, propose a cross-browser service-based simulation analytics platform to analyze environment layouts with respect to occupancy and activity. Their platform allows users to access simulation services by uploading 3D environment models in numerous common formats, devise targeted simulation scenarios, run simulations, and instantly generate crowd-based analytics for their designs. The authors conducted a case study to showcase cross-domain applicability of their service-based platform, and a user study to evaluate the usability of this approach. In the third paper, Junxuan Bai, Rong Dai, Ju Dai, and Junjun Pan, from Beihang University in Beijing, and Peng Cheng Laboratory in Shenzhen, all in China propose a hybrid feature for emotional classification in dance performances. The hybrid feature is composed of an explicit feature and a deep feature. The explicit feature is calculated based on the Laban movement analysis, which considers the body, effort, shape, and space properties. The deep feature is obtained from latent representation through a 1D convolutional autoencoder. Eventually, the authors present an elaborate feature fusion network to attain the hybrid feature that is almost linearly separable. The abundant experiments demonstrate that their hybrid feature is superior to the separate features for the emotional classification in dance performances. The fourth paper, by Donya Ghafourzadeh, Sahel Fallahdoust, Cyrus Rahgoshay, André Beauchamp, Adeline Aubame, Eric Paquette, from Ecole de technologie supérieure, and Tiberiu Popa, from Concordia University, all in Montreal, Canada, present an approach to construct realistic 3D facial morphable models (3DMM) that allows an intuitive facial attribute editing workflow. They created a 3DMM by combining local part-based 3DMM for the eyes, nose, mouth, ears, and facial mask regions. Their local PCA-based approach uses a novel method to select the best eigenvectors from the local 3DMM to ensure that the combined 3DMM is expressive, while allowing accurate reconstruction. They provide different editing paradigms, all designed from the analysis of the data set. Their part-based 3DMM is compact, yet accurate, and compared to other 3DMM methods, it provides a new trade-off between local and global control. The results show that their part-based 3DMM approach has excellent generative properties and allows the user intuitive local control. The last paper by David Antonio Gomez Jauregui, from Ecole Supérieure des Technologies Industrielles Avancées, in Bidart, France, Tom Giraud, from University of Augsburg in Germany, Brice Isableu, from Aix-Marseille University, in Aix-en-Provence, France and Jean-Claude Martin, from LIMSI-CNRS, in Orsay, France propose a library of motion-captured movements that interviewers are most likely to display. They designed a fully automatic interactive virtual agent able to display these movements in response to the bodily movements of the user. Thirty-two participants presented themselves to this virtual agent during a simulated job interview. The authors explain the different hypotheses used (1) comparison between the performance of participants with human interviewers and the performance of participants with virtual interviewers, (2) comparison between mirror and random postural behaviors displayed by a female vs. a male virtual interviewer, (3) correlation between the participants' performance and their personality traits.

This article devises a photograph-based monitoring model to estimate the real-time PM2.5concentrations, overcoming currently popular electrochemical sensor-based PM2.5monitoring methods’ shortcomings such as low-density spatial distribution and time delay. Combining the proposed monitoring model, the photographs taken by various camera devices (e.g., surveillance camera, automobile data recorder, and mobile phone) can widely monitor PM2.5concentration in megacities. This is beneficial to offering helpful decision-making information for atmospheric forecast and control, thus reducing the epidemic of COVID-19. To specify, the proposed model fuses Information Abundance measurement and Wide and Deep learning, dubbed as IAWD, for PM2.5monitoring. First, our model extracts two categories of features in a newly proposed DS transform space to measure the information abundance (IA) of a given photograph since the growth of PM2.5concentration decreases its IA. Second, to simultaneously possess the advantages of memorization and generalization, a new wide and deep neural network is devised to learn a nonlinear mapping between the above-mentioned extracted features and the groundtruth PM2.5concentration. Experiments on two recently established datasets totally including more than 100 000 photographs demonstrate the effectiveness of our extracted features and the superiority of our proposed IAWD model as compared to state-of-the-art relevant computing techniques.

This issue contains four papers. In the first paper, Xiao Zhang and Deling Yang, from Guangzhou Academy of Fine Arts in China, propose a study to explore how online museums distribute the postproduction of cultural knowledge related to artworks in a network society. This study has implications for how online museums will adapt to the future development of knowledge societies. The core innovation of this study is exploring distributed knowledge postproduction in online museums from the perspective of Mode 2 knowledge production and online distributed knowledge production. This study also examines distributed knowledge postproduction in online museums, which coconstructs knowledge and meaning. In the second paper, Bin Wang, Weibin Liu, and Weiwei Xing, from Beijing Jiaotong University, China, propose an automatic segmentation method based on geodesic by introducing Riemannian manifold. They convert Mo-cap data from Euler angles into quaternions, calculate the intrinsic mean of the motion sequence, hemispherize quaternions, and use logarithmic and exponential mapping to calculate geodesic distances instead of quaternions. The experimental results show that the algorithms can achieve automatic segmentation and have a better segmentation effect. In the third paper, Jure Demšar and Iztok Lebar Bajec, from University of Ljubljana, Slovenia and Will Blewitt, from Coventry University, UK, present a hybrid model for the simulation of herds of grazing sheep. The novel approach called hybrid modeling tries to mix the best of both worlds—precision of individual based models and speed of flow based ones. Through Bayesian data analysis, the authors show that they can encompass several aspects of real-world sheep behavior. Their hybrid model is also extremely efficient, capable of simulating herds of more than 1000 individuals in real-time without resorting to GPU execution. In the last paper, Wei Cao, Zhixin Yang, Xiaohua Ren, Luan Lyu, and Bob Zhang, from University of Macau, China; Yanci Zhang, from Sichuan University in Chengdu, China; and Enhua Wu, from University of Macau and Chinese Academy of Sciences in Beijing, China, introduce an improved approach to simulate nonorthotropic geometric models under large deformation. The improvements are mainly twofold. First, a frame-field is specified on a given undeformed object, that is, each point of the object is equipped with a frame. Second, they design the deformation properties along each axis in the local nonorthogonal coordinate to get a local constitutive model. To improve the stability, they introduce a time-varying method to simultaneously track the local coordinates reorientation by pushing forward the original frame-field to the deformed frame-field.

This issue contains three papers. In the first paper, Manoj Kumar Muni and Dayal R. Parhi, from the National Institute of Technology in Rourkela, India, and Priyadarshi Biplab Kumar, from the National Institute of Technology in Hamirpur, India, consider the use of gray wolf optimization controller (GWOC) as a multiobjective technique for multiple humanoid navigation. Upon activation of GWOC, the humanoids mimic the group hunting behavior of gray wolves and navigate toward the target in a collision-free manner in the presence of both static and dynamic hurdles. The wolves in the pack will either diverge for searching prey or converge together for attacking the prey following the best search agent. GWOC is able to keep the humanoid free from being trapped in local minima, whereas it facilitates it to head toward global minima. GWOC provides better results than other intelligent techniques because of its five characteristics: safe boundary, protection, following, hunting, and caring. In the second paper, Lianyao Wu, Wanggen Wan, Xiaoqing Yu, Chunkai Ye, and A.A.M. Muzahid, from Shanghai University, China, present a real-time augmented reality framework based on a semidense method with CPU. Specifically, the semidense method searches pixels with high gradients in each keyframe and estimates accurate depths by fusing matching pixels in other keyframes. The authors propose an outlier removal method that excludes 3D points outside the camera trajectory. By integrating this method, their framework preserves clean edges of the real environment. The experimental results on the data set show that their proposed framework has better surface reconstruction accuracy than other methods and their tracking thread runs in an acceptable speed when the semidense mapping thread runs backend. With the benefit of the robust camera and the aligned surface, virtual characters of their AR application enable realistic movement and collision. In the last paper, Jongmin Kim, from Kangwon National University in Chuncheon, Korea, Yeongho Seol, from Weta Digital Ltd in Wellington, New Zealand, and Hoemin Kim and Taesoo Kwon, from Hanyang University, Korea, present a novel interactive inverse kinematics (IK) framework that automatically and efficiently handles various types of collisions and spatial relationship. For the collision handling, they suggest a new type of linear constraint (half-space constraint) and a novel collision-response strategy based on gradual constraint accumulation. Specifically, the constraints that were used in the previous iterations continue to be used while more constraints are added to finally resolve the collisions. This approach also allows the user to edit human motion without any repetitive procedures and tuning the parameters. Regarding the spatial relationship, the authors provide another linear constraint that preserves complex spatial relationships between body parts. Their approach is novel in that both half-space constraints for collision handling and relative constraints for pose editing are embedded into an IK solver.

This issue contains three papers. In the first paper, M. Hassaballah, Abdelraheem M. Aly, and Ahmad Abdelnaim, from South Valley University Qena, Egypt, propose for the Interactive simulations of fluids flow to obtain the stable pressure from modifications in the source term of pressure Poisson equation (PPE). The particles disorders are solved using a shifting technique with the current treatment of source term in PPE. In addition, the dummy boundary particles are used for the rigid boundary treatment. Performance of the stabilized ISPH model is tested on various numerical simulations with largely distorted free surface including liquid sloshing problems, fluid–fluid, fluid–structure interactions and dam-break over horizontal and inclined plane. To extend the applicability of the stabilized ISPH model, the postprocess including visual realism with the highly rendering scheme is coupled. In the second paper, Xianxuan Lin, Wang Xun, Jinyu Li, Bailin Yang, Kaili Zhang, Tianxiang Wei, from Zhejiang Gongshang University in Hangzhou, China, and Frederick W. B. Li, from Durham University, UK, propose a color migration framework for home scene images. It picks the coloring from a template image and transforms such coloring to a home scene image through a simple interaction. Their framework comprises three main parts. First, they carry out an interactive segmentation to divide an image into local regions and extract their corresponding colors. Second, they generate a matching color table by sampling the template image according to the color structure of the original home scene image. Finally, they transform colors from the matching color table to the target home scene image with boundary transition maintained. Experiment results demonstrated their framework can produce aesthetically attractive home scene coloring. In the last paper, Xiaoyu Cui, Ruifan Cai, Xiangjun Tang, Xiaogang Jin, from Zhejiang University, in Hangzhou, China, and Zhigang Deng, from University of Houston, Texas, United States, propose a novel shape-constrained fireworks simulation method with rich textures in a helmet-mounted display virtual environment using sketched feature lines as input. Their approach first retrieves an object from a three-dimensional (3D) model database using a sketch-based 3D shape retrieval algorithm. Then, in order to approximate models with complex structures, they introduce a novel point sampling algorithm based on Gaussian curvatures, which stores not only the positions of the selected vertices but also the texture (UV) coordinates information for texture display. In addition, they introduce a multilevel explosion process so that the fireworks can dynamically form specific, visually pleasing shapes. Through their experiments, they demonstrate that their approach can produce better results than state-of-the-art approaches.

This special issue contains 28 full papers selected from the Computer Animation and Social Agents 2020 Conference (CASA2020). This conference was founded by the Computer Graphics Society in 1988 in Geneva and is the oldest conference on Computer Animation in the world. It has been held in many countries around the world and in recent years in Beijing, China (2018), Paris, France (2019) and this year in Bournemouth, United Kingdom. Because of the Covid-19 pandemic, this year, the conference will be held online through the Youtube Channel. The best paper award will be announced on the conference website after the conference. We would like to thank the authors for sharing their research findings by submitting papers to CASA2020. We are very grateful to the Program Committee members for reviewing the papers and to all the people who have contributed to the success of CASA2020 in Bournemouth. The conference is organized by Bournemouth University under the guidance of the Computer Graphics Society (CGS). Conference co-chairs Jian Jun Zhang (Bournemouth University, UK) Nadia Magnenat Thalmann (University of Geneva, Switzerland and Nanyang Technological University, Singapore) Program co-chairs Daniel Thalmann (EPFL, Switzerland) Xiaosong Yang (Bournemouth University, UK) Weiwei Xu (Zhejiang University, China) Publicity chair Jian Chang (Bournemouth University, UK) Local chair Feng Tian (Bournemouth University, UK) International program committee Nadine Aburumman, Brunel University, UK Norman Badler, University of Pennsylvania, USA Selim Balcisoy, Sabanci University, Turkey Loic Barthe, IRIT—Université de Toulouse, France Jan Bender, RWTH Aachen University, Germany Raphaëlle Chaine, LIRIS Université Lyon 1, France Jian Chang, Bournemouth University, UK Fred Charles, Bournemouth University, UK Parag Chaudhuri, Indian Institute of Technology, Bombay, India Marc Christie, INRIA, France Justin Dauwels, Nanyang Technological University, Singapore Shujie Deng, King's College London, UK Zhigang Deng, University of Houston, USA Etienne de Sevin, SANPSY University of Bordeaux, France Petros Faloutsos, York University, Canada Christos Gatzidis, Bournemouth University, UK Ugur Gudukbay, Bilkent University, Turkey Shihui Guo, Xiamen University, China Xiaohu Guo, The University of Texas at Dallas, USA James Hahn, George Washington University, USA Carlo Harvey, Birmingham City University, UK Gaoqi He, East China Normal University, China Ying He, Nanyang Technological University, Singapore Kemao Qian, Nanyang Technological University, Singapore Ruizhen Hu, Shenzhen University, China Jinyuan Jia, Tongji University, China Tao Jiang, University of Surrey, UK Xiaogang Jin, Zhejiang University, China Marcelo Kallmann, University of California, Merced, USA Prem Kalra, IIT Delhi, India Dongwann Kang, Seoul National University of Science and Technology, Korea Mubbasir Kapadia, Rutgers University, USA Min H. Kim, Korea Advanced Institute of Science and Technology, Korea Scott King, Texas A&M University—Corpus Christi, USA Taesoo Kwon, Hanyang University, China Sung-Hee Lee, Korea Advanced Institute of Science and Technology, Korea Wonsook Lee, University of Ottawa, Canada Tsai-Yen Li, National Chengchi University, Taiwan Guoliang Luo, East China Jiaotong University, China Chongyang Ma, Snap Inc., USA Anderson Maciel, Universidade Federal do Rio Grande do Sul, Brazil Nadia Magnenat Thalmann, University Of Geneva, Switzerland Shigeo Morishima, Waseda University, Japan Soraia Musse, Pontificia Universidade Catolica do Roi Grande do Sul, PUCRS, Brazil Rahul Narain, Indian Institute of Technology, Delhi, India Junjun Pan, Beihang University, China Nuria Pelechano, Universitat Politècnica de Catalunya, Spain Julien Pettre, INRIA, France Nicolas Pronost, Université Claude Bernard Lyon 1, France Kun Qian, King's College London, UK Craig Schroeder, University of California, Riverside, USA Ari Shapiro, Embody Digital, USA Hubert P. H. Shum, Northumbria University, UK Shinjiro Sueda, Texas A&M University, USA Daniel Thalmann, Ecole Polytechnique Fédérale de Lausanne, Switzerland Feng Tian, Bournemouth University, UK Yiying Tong, Michigan State University, USA Meili Wang, Northwest A&F University, China Zhao Wang, Zhejiang University, China Enhua Wu, University of Macau & ISCAS, China Zhongke Wu, Beijing Normal University, China Weiwei Xu, Zhejiang University, China Yachun Fan, Beijing Normal University, China Bailin Yang, Zhejiang Gongshang University, China Yin Yang, University of New Mexico, USA Xiaosong Yang, Bournemouth University, UK Yuting Ye, Oculus Research, USA Lihua You, Bournemouth University, UK Hongchuan Yu, Bournemouth University, UK Zerrin Yumak, Utrecht University, Netherlands Wenshu Zhang, Cardiff Metropolitan University Jian Zhang, Bournemouth University, UK Jianmin Zheng, Nanyang Technological University, Singapore

In this work, we resolve a big challenge that most current image quality metrics (IQMs) are unavailable across different image contents, especially simultaneously coping with natural scene (NS) images or screen content (SC) images. By comparison with existing works, this paper deploys on-line and off-line data for proposing a unified no-reference (NR) IQM, not only applied to different distortion types and intensities but also to various image contents including classical NS images and prevailing SC images. Our proposed NR IQM is developed with two data-driven learning processes following feature extraction, which is based on scene statistic models, free-energy brain principle, and human visual system (HVS) characteristics. In the first process, the scene statistic models and an image retrieve technique are combined, based on on-line and off-line training instances, to derive a novel loose classifier for retrieving clean images and helping to infer the image content. In the second process, the features extracted by incorporating the inferred image content, free-energy and low-level perceptual characteristics of the HVS are learned by utilizing off-line training samples to analyze the distortion types and intensities and thereby to predict the image quality. The two processes mentioned above depend on a gigantic quantity of training data, much exceeding the number of images applied to performance validation, and thus make our model's performance more reliable. Through extensive experiments, it has been validated that the proposed blind IQM is capable of simultaneously inferring the quality of NS and SC images, and it has attained superior performance as compared with popular and state-of-the-art IQMs on the subjective NS and SC image quality databases. The source code of our model will be released with the publication of the paper at https://kegu.netlify.com.

No abstract is available for this article.

This issue contains six papers.In the first paper, Nuttapon Vanakittistien, Attawith Sudsang, and Nuttapong Chentanez from Chulalongkorn University, Bangkok, Thailand, and NVIDIA, Zurich, Switzerland, propose a system for creating a hair model that matches a user's hairstyle from images.The model consists of guide hair strands and can be used in a real-time hair simulator.The goal differs from most previous works, which aim to create realistic high-resolution hair for offline applications or create mesh of the exterior of the hair volume for image manipulation.The primary aim is for a user to be able to put his/her hairstyle into a game or other real-time applications.By taking photos in eight views of the user's head using a smartphone camera and segmenting images with some easy-to-use tools, the player will obtain his/her own hair model in NVIDIA's HairWorks, which is a hair simulator used in many games.The authors show a number of results demonstrating the capabilities of their system in this paper.In the second paper, Priyadarshi Biplab Kumar, Saktiswarup Mohapatra, and Dayal R. Parhi from the National Institute of Technology Rourkela, Odisha, India, present an investigation dealing with the path planning of NAO humanoid robots.In the present work, a classical method of regression analysis and an artificial intelligence technique of fuzzy logic are implemented separately for the purpose of obstacle avoidance during the motion of humanoid NAOs towards respective targets.The simulation analysis of the proposed techniques is carried out using V-REP software.The experiments are performed in laboratory conditions with a proper environment for working on the humanoid NAOs.Finally, a comparison has been made between the simulation and experimental results.The results obtained from the simulation and experimental analyses are in good agreement with each other, which suggest that the proposed methodologies can be used as methods of robust control for the navigation of humanoids.In the third paper, Lin Wang and Soonhung Han from KAIST, Daejeon, Korea, conducted research related to the design for a realistic motion visualization system based on numerical simulation data using a commercial game engine (Unity 3D).In their system, the six-degree-of-freedom motion (Surge, Sway, Heave, Roll, Pitch, and Yaw) is simulated and visualized based on numerical analysis results of two hydrodynamics simulation softwares, which can illuminate the nuance between simulation results and experiment results and provide a "real-time" visual experience about motion in each direction.Meanwhile, comprehensive sea environment conditions, such as wind, rain, water, sound, and cloudiness, are also visualized in Unity 3D.

This special issue contains 26 full papers selected from the Computer Animation and Social Agents 2019 (CASA'2019) Conference. This conference was founded by the Computer Graphics Society in 1988 in Geneva and is the oldest conference on computer animation in the world. It has been held in various countries around the world, in recent years, in Seoul, South Korea (2017); Beijing, China (2018); and this year, in Paris, France. This year, the conference is organized jointly with ACM Intelligent Virtual Agents (ACM IVA 2019). They started the conference with two days of presentations of technical papers, followed by a one-day tutorial on “Modelling interaction between real humans and virtual humans or social robots” and “Capturing real-world data for characters, sometimes with machine learning,” and a workshop on “Crowd analysis and applications: Simulations meet video analytics.” Addressing this year's conference are two invited speakers: (1) Professor Marie-Paule Cani from Ecole Polytechnique, Paris, France, and (2) Dr. Thabo Beeler from Disney Research in Zürich, Switzerland. During the social dinner, the best paper award will be announced. We would like to thank the authors for having submitted a paper to CASA'2019, the program committee members, and all the people who have contributed to the success of CASA'2019 in Paris. The conference is organized by Centre National de la Recherche Scientifique (CNRS) and Sorbonne University, in cooperation with ACM-SIGGRAPH, under the guidance of the Computer Graphics Society (CGS).

VRLAB

In this paper, we present a novel method for real-time 3D hand pose estimation from single depth images using 3D Convolutional Neural Networks (CNNs). Image-based features extracted by 2D CNNs are not directly suitable for 3D hand pose estimation due to the lack of 3D spatial information. Our proposed 3D CNN-based method, taking a 3D volumetric representation of the hand depth image as input and extracting 3D features from the volumetric input, can capture the 3D spatial structure of the hand and accurately regress full 3D hand pose in a single pass. In order to make the 3D CNN robust to variations in hand sizes and global orientations, we perform 3D data augmentation on the training data. To further improve the estimation accuracy, we propose applying the 3D deep network architectures and leveraging the complete hand surface as intermediate supervision for learning 3D hand pose from depth images. Extensive experiments on three challenging datasets demonstrate that our proposed approach outperforms baselines and state-of-the-art methods. A cross-dataset experiment also shows that our method has good generalization ability. Furthermore, our method is fast as our implementation runs at over 91 frames per second on a standard computer with a single GPU.

Vision-based hand pose estimation is important in human-computer interaction. While many recent works focus on full degree-of-freedom hand pose estimation, robust estimation of global hand pose remains a challenging problem. This paper presents a novel algorithm to optimize the leaf weights in a Hough forest to assist global hand pose estimation with a single depth camera. Different from traditional Hough forest, we propose to learn the vote weights stored at the leaf nodes of a forest in a principled way to minimize average pose prediction error, so that ambiguous votes are largely suppressed during prediction fusion. Experiments show that the proposed method largely improves pose estimation accuracy with optimized leaf weights on both synthesis and real datasets and performs favorably compared to state-of-the-art convolutional neural network-based methods. On real-world depth videos, the proposed method demonstrates improved robustness compared to several other recent hand tracking systems from both industry and academy. Moreover, we utilize the proposed method to build virtual/augmented reality applications to allow users to manipulate and examine virtual objects with bare hands.

Behavioral realism and realistic interactions are major criteria for improving social presence in virtual reality environments. We focus on multi-party VR applications where computer agents and avatars interact, share and collaborate with each other using objects. Our formulation employs realistic animations to simulate human-like behavioral motions of computer agents while they interact with avatars to enhance the sense of social presence in the VR environment. We exemplify our proposed model in a VR volleyball game setup. We model specific underlying interactions like gazing, collision detection and miscellaneous reactions (like how to pick a volleyball, how to transfer the ball to server) between computers players and avatars in the VR Volleyball game. We conduct a preliminary user survey to illustrate the significance of inclusion of realistic interactions for improving sense of social presence in a multi-party VR environment.

When building robotic hands, researchers are always face with two main issues of how to make robotic hands look human-like and how to make robotic hands function like real hands. Most existing solutions solve these issues by manually modelling the robotic hand [10-18]. However, the design processes are long, and it is difficult to duplicate the geometry shape of a human hand. To solve these two issues, this paper presents a simple and effective method that combines 3D printing and digitization techniques to create a 3D printable cable-driven robotic hand from scanning a physical hand. The method involves segmenting the 3D scanned hand model, adding joints, and converting it into a 3D printable model. Comparing to other robotic solutions, our solution retains more than 90% geometry information of a human hand1, which is attained from 3D scanning. Our modelling progress takes around 15 minutes that include 10 minutes of 3D scanning and five minutes for changing the scanned model to an articulated model by running our algorithm. Compared to other articulated modelling solutions [19, 20], our solution is compatible with an actuation system which provides our robotic hand with the ability to mimic different gestures. We have also developed a way of representing hand skeletons based on the hand anthropometric. As a proof of concept, we demonstrate our robotic hand's performance in the grasping experiments.

• SBGames is the largest and most important scientific event for games and digital entertainment in Latin America. • It is attended by scientists, artists, designers, teachers and students from Colleges, Universities and the Game Industry. • It gathers around a thousand participants from different regions of Brazil and Countries as United States, England and Portugal. • SBGames is an In-Cooperation event of Eurographics and ACM SIGGRAPH and in 2018 it is held in the beautiful city of Foz do Iguaçu in a jointly conference.

This issue contains six papers.In the first paper, Kim J. L. Nevelsteen from Stockholm University proposes to sample technologies using grounded theory and obtained a definition for a "virtual world" that is directly applicable to technology.The obtained definition is compared with related work and used to classify advanced technologies, such as a pseudo-persistent video game, a MANet, a virtual and mixed reality, and the Metaverse.The results of this article include: a breakdown of properties that set apart various technologies; a definition that is validated by comparing it with other definitions; an ontology showing the relation of different complimentary terms and acronyms; and, the usage of pseudo-persistence to categories of those technologies that only mimic persistence.

This issue contains five papers. In the first paper, Bartlomiej Waszak, from Quebec City, Canada, proposes a novel approach to limbless movement simulation. The author built a simulation framework using position-based dynamics. He describes the body configuration of snakes using different types of distance constraints. The limbless movement is based on the formulation of a friction constraint to model the behavior of a snake's scales. In this approach, it is easy to solve collisions between objects and self-collisions for simulated snakes. The model includes a dynamic geometrical environment colliding with simulated animals. Detailed patterns are presented for four main types of limbless movement: serpentine, rectilinear, concertina, and sidewinding. In the second paper, Min Jiang, Richard Southern, and Jian J Zhang, from Bournemouth University, UK, present a novel and unified particle-based method for real-time dissolution simulation, which is fast, predictable, independent of sampling resolution, and visually plausible. The dissolution model is derived from collision theory and integrated into a smoothed particle hydrodynamics (SPH) fluid solver. Dissolution occurs when a solute is submerged in solvent. Physical laws govern the local excitation of solute particles based on kinetic energy. Solute separation during dissolution is handled using a new GPU-based region growing method. The use of SPH sampling for both solute and solvent guarantees a predictable and smooth dissolution process and provides user control of the volume change during the phase transition. In the third paper. Ashish Dhiman, Dhaval Solanki, and Uttama Lahiri, from The Indian Institute of Technology Gandhinagar in Gujarat, India; Ashu Bhasin, from All India Institute of Medical Sciences, in Delhi, India; and Abhijit Das, from AMRI Institute of Neuroscience, in Kolkata, India, describe the design of a novel, multimodal, virtual-reality-based, and performance-sensitive exercise platform that can intelligently adapt its task presentation to one's performance. Here, the authors aim to address unilateral shoulder abduction and adduction that are essential for the performance of daily living activities. They designed an experimental study in which six chronic stroke survivors participated. While they interacted with the virtual-reality-based tasks, the authors recorded the physiological signals in a synchronized manner. In the fourth paper, Xiaoyong Zhang and Shiguang Liu, from Tianjin University, China, propose a novel interactive SPH fluid control framework with turbulent details. The authors run SPH fluid simulation on CUDA and greatly improve the efficiency of fluid control. The control particle with curvature framework was adapted in this paper. The authors specially designed spring forces to make the fluid match a fast moving control target. Moreover, fine fluid details were preserved by separately calculating the under-control fluid turbulence and the free fluid turbulence. This improved SPH fluid control can run in real time, which can enhance the visual quality of fluid animation as well. In the fifth paper, Dayal R.Parhi, Chinmaya Sahu, and Priyadarshi Biplab Kumar, from The National Institute of Technology Rourkela in Orissa, India, present a navigation strategy for humanoid robots using a hybridized technique consisting of adaptive particle swarm optimization and adaptive ant colony optimization. Here, the governing parameters of the adaptive ant colony optimization technique are optimized by using adaptive particle swarm optimization method. These optimized parameters are subsequently used by the adaptive particle swarm optimization technique to get the final turning angle by which the humanoid navigates in a cluttered environment. Here, navigation is performed in both static and dynamic environments. To avoid the intercollision among the humanoids, a Petri net controller has been designed and implemented along with the proposed hybridized method.

This issue contains six papers.In the first paper, Christos Kyrlitsias and Despina Michael-Grigoriou, from the Cyprus University of Technology in Limassol, Cyprus, investigate the conformity to virtual humans in an immersive virtual environment using two experiments.In the first experiment, they study whether agents have social influence on the participants by conducting the Asch conformity experiment.In the second experiment, they use a similar method to study how the factors "agency" and "behavioral realism" affect social conformity.The results of the experiment show that conformity can be caused by virtual humans in immersive virtual environments.

Articulated hand pose estimation is one of core technologies in human-computer interaction. Despite the recent progress, most existing methods still cannot achieve satisfactory performance, partly due to the difficulty of the embedded high-dimensional nonlinear regression problem. Most existing data-driven methods directly regress 3D hand pose from 2D depth image, which cannot fully utilize the depth information. In this paper, we propose a novel multi-view convolutional neural network (CNN)-based approach for 3D hand pose estimation. To better exploit 3D information in the depth image, we project the point cloud generated from the query depth image onto multiple views of two projection settings and integrate them for more robust estimation. Multi-view CNNs are trained to learn the mapping from projected images to heat-maps, which reflect probability distributions of joints on each view. These multi-view heat-maps are then fused to estimate the optimal 3D hand pose with learned pose priors, and the unreliable information in multi-view heat-maps is suppressed using a view selection method. Experimental results show that the proposed method is superior to the state-of-the-art methods on two challenging data sets. Furthermore, a cross-data set experiment also validates that our proposed approach has good generalization ability.

New challenges have been brought out along with the emerging of 3D-related technologies, such as virtual reality, augmented reality (AR), and mixed reality. Free viewpoint video (FVV), due to its applications in remote surveillance, remote education, and so on, based on the flexible selection of direction and viewpoint, has been perceived as the development direction of next-generation video technologies and has drawn a wide range of researchers' attention. Since FVV images are synthesized via a depth image-based rendering (DIBR) procedure in the "blind" environment (without reference images), a reliable real-time blind quality evaluation and monitoring system is urgently required. But existing assessment metrics do not render human judgments faithfully mainly because geometric distortions are generated by DIBR. To this end, this paper proposes a novel referenceless quality metric of DIBR-synthesized images using the autoregression (AR)-based local image description. It was found that, after the AR prediction, the reconstructed error between a DIBR-synthesized image and its AR-predicted image can accurately capture the geometry distortion. The visual saliency is then leveraged to modify the proposed blind quality metric to a sizable margin. Experiments validate the superiority of our no-reference quality method as compared with prevailing full-, reduced-, and no-reference models.

With the quick development and popularity of computers, computer-generated signals have drastically invaded into our daily lives. Screen content image is a typical example, since it also includes graphic and textual images as components as compared with natural scene images which have been deeply explored, and thus screen content image has posed novel challenges to current researches, such as compression, transmission, display, quality assessment, and more. In this paper, we focus our attention on evaluating the quality of screen content images based on the analysis of structural variation, which is caused by compression, transmission, and more. We classify structures into global and local structures, which correspond to basic and detailed perceptions of humans, respectively. The characteristics of graphic and textual images, e.g., limited color variations, and the human visual system are taken into consideration. Based on these concerns, we systematically combine the measurements of variations in the above-stated two types of structures to yield the final quality estimation of screen content images. Thorough experiments are conducted on three screen content image quality databases, in which the images are corrupted during capturing, compression, transmission, etc. Results demonstrate the superiority of our proposed quality model as compared with state-of-the-art relevant methods.

We propose a simple, yet effective approach for real-time hand pose estimation from single depth images using three-dimensional Convolutional Neural Networks (3D CNNs). Image based features extracted by 2D CNNs are not directly suitable for 3D hand pose estimation due to the lack of 3D spatial information. Our proposed 3D CNN taking a 3D volumetric representation of the hand depth image as input can capture the 3D spatial structure of the input and accurately regress full 3D hand pose in a single pass. In order to make the 3D CNN robust to variations in hand sizes and global orientations, we perform 3D data augmentation on the training data. Experiments show that our proposed 3D CNN based approach outperforms state-of-the-art methods on two challenging hand pose datasets, and is very efficient as our implementation runs at over 215 fps on a standard computer with a single GPU.

Negative symptoms of schizophrenia significantly affect the daily functioning of patients, especially movement and expressive gestures. The diagnosis of such symptoms is often difficult and require the expertise of a trained clinician. Apart from these subjective methods, there is little research on developing objective methods to quantify the symptoms. Therefore, we explore body movement signals as objective measures of negative symptoms. Specifically, we extract the signals from video recordings of patients being interviewed. We analysed the interviews of 69 paid participants (46 patients and 23 healthy controls) in this study. Correlation between movement signals (linear and angular speeds of upper limbs and head, acceleration and gesture angles) and subjective ratings (assigned during same interview) from the NSA-16 scale were calculated. As hypothesized, the movement signals correlated strongly with the movement impairment aspect of the NSA-16 questionnaire. Also, not quite surprisingly, strong correlations were obtained between the movement signals and speech items of NSA-16, indicating lack of associated gestures in patients during speech. These subjective ratings could also be reasonably predicted from the objective signals with an accuracy of 61-78% using machine-learning algorithms with leave-one-out cross-validation technique. Furthermore, these objective measures can be reliably utilized to distinguish between the patient and healthy groups, as supervised learning methods can classify the two groups with 74-87% accuracy.

course Share on Real humans with virtual humans and social robots interactions (HCI) Authors: Daniel Thalmann EPFL, Switzerland EPFL, SwitzerlandView Profile , Nadia Magnenat Thalmann NTU, Singapore NTU, SingaporeView Profile , Manoj Ramanathan NTU, Singapore NTU, SingaporeView Profile Authors Info & Claims SA '17: SIGGRAPH Asia 2017 CoursesNovember 2017 Article No.: 15Pages 1–221https://doi.org/10.1145/3134472.3134513Published:27 November 2017Publication History 0citation237DownloadsMetricsTotal Citations0Total Downloads237Last 12 Months26Last 6 weeks5 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

This issue contains five papers. In the first paper, Angel Zaldivar Pino, Manuel Gonzalez Bedia, and Francisco J. Seron, from Universidad Zaragoza, Spain, present a simulation framework in which the agents are endowed with a sensing device, an oscillator network as controller, and actuators to interact with the environment. The perception device is designed as an optic array emulating the principles of the animal retina, which assimilates stimuli resembling optic flow to be captured from the environment. The controller modulates informational variables to action variables in a sensory motor flow. Their approach is based on the Kuramoto model that describes mathematically a network of coupled phase oscillators and the use of evolutionary algorithms, which is proved to be capable of synthesizing minimal synchronization strategies based on the dynamical coupling between agents and environment. In the second paper, Congkun Chen, Yun Sheng, Fang Li, Guixu Zhang, from East China Normal University, Shanghai, China, and Hassan Ugail, from University of Bradford, UK, propose an extension of the use of the partial differential equation (PDE) method to head visualization with CT data and show how the two primary medical visualization means, surface reconstruction, and volume rendering can be integrated into one single framework through PDEs. Their scheme first performs head segmentation from CT slices using a variational approach; with the extracted boundary conditions, head surface reconstruction is then executed. Since only a few slices are used, their method can perform head surface reconstruction more efficiently in both computational time and storage cost than the widely used marching cubes algorithm. By elaborately introducing a third parameter ω to the PDE method, a solid head can be created, based on which the head volume is subsequently rendered with 3-D texture mapping. In the third paper, Francis Laclé, Utrecht University, the Netherlands, and Nicolas Pronost, Université Claude Bernard, Lyon, France, focus on combining, by a controllable enhancement process, a functional and biomechanical model of musculotendon units with its high-resolution geometrical counterpart. The method was developed in order to be invariant to spatial and polygonal configurations and to be scalable in both longitudinal and latitudinal directions. Results with 48 musculotendon units for the lower body show a drop of 84% with respect to the number of vertices when compared to the high-resolution model, while maintaining the functional information. A real-time simulation experiment resulted in a runtime of 135 Hz. Sergio Orts-Escolano, from University of Alicante, Spain, Johannes Bastiaan Boom, Xin Xin Ning, Steven McDonagh, Peter Sandilands, and Robert B. Fisher, from University of Edinburgh, UK, propose in the fourth paper, the first hybrid CPU-GPU based method for estimating a point light source position in a scene recorded by an RGB-D camera. The image and depth information from the Kinect is enough to estimate a light position in a scene, which allows for the rendering of synthetic objects into a scene that appear realistic enough for augmented reality purposes. This method does not require a light probe or other physical device. To make this method suitable for augmented reality, the authors developed a hybrid implementation that performs light estimation in less than 1 s. By rendering synthetic objects into the recorded scene, they illustrate that this accuracy is good enough for the rendered objects to look realistic. Finally, Jorge Eduardo Ramirez Flores and Antonio Susin Sanchez, from Universitat Politecnica de Catalunya, Barcelona, Spain, present an approach based on mesh segmentation for skinning and skeleton-driven computer animation. They propose a novel and fast method, based in watershed segmentation to deal with characters in T-Pose and arbitrary poses; they also introduce a simple weight assign algorithm based in the rigid skinning obtained with the segmentation algorithm for the linear blend skinning (LBS) deformation method. They ultimately propose a modified version of the LBS that avoids the loss of volume in twist rotations using the segmentation stage output values.

This issue contains six papers. In the first paper, Jong-Hyun Kim and Chang-Hun Kim, Korea University, Seoul, and Jung Lee, Hallym University, Gangwon-do, Republic of Korea, present a new method for the fast simulation of interactions between fluids and solids by incorporating particle-based water flow into an adaptive signed distance field (ADF). This paper addresses the problem of “tunneling” artifact, in which particles with high velocities skip across the layer of leaf nodes by (i) considering particles only on the leaf nodes in the adaptive structure to improve the processing time required for the water–solid coupling and (ii) considering the water flow to avoid the tunneling artifact by incorporating particle motion into the tree structure of the ADF. In the second paper, Rodrigo Guillermo Baravalle and Leonardo Scandolo, Universidad Nacional de Rosario, Argentina; Claudio Delrieux, Universidad Nacional del Sur, Buenos Aires, Argentina; Cristian García Bauza, Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina; and Elmar Eisemann, Delft University of Technology, The Netherlands, propose an algorithm for the procedural generation of porous materials based on a simulation of the growth of self-avoiding bubbles inside a volume, by means of dynamical systems. This simulation generates 3D textures that adequately represent porous materials, which are then rendered by means of a GPU-based direct volume rendering method. The patterns induced by the bubbles can be intuitively controlled. The bubbles adapt to any given shape and have convincing global and local fluid-like patterns as seen in bread and sponges. In the third paper, Andre Possani-Espinosa, J. Octavio Gutierrez-Garcia, and Isaac Vargas Gordillo, Instituto Tecnológico Autónomo de México, lay the foundations for the design of believable virtual drivers by proposing a methodology for profiling players using the open racing car simulator. Data collected from 125 players about their driving behaviors and personality traits give insights into how personality traits should model the behavior of believable virtual drivers. The data analysis was conducted using a correlation analysis and the J48 decision tree algorithm. In addition, this work also (i) gives preliminary insights into the relationship between the driving behavior and personality of racing game players and actual car drivers and (ii) presents evidence of the relevance of gender as a predictor of personality traits of racing game players. Monssef Alsweis, Universitat Konstanz, Germany, suggests, in the fourth paper, a procedural biologically motivated method to simulate the development of leaf contours and the generation of different levels of leaf venation systems. Visually realistic development is described by a growth function RERG that reacts to hormone (Auxin) sources embedded in the leaf blade. The shape of the leaf is determined by a set of feature points at the leaf contour. The contour is extracted from images utilizing a Curvature Scale Space Corner Detection Algorithm. Auxin transport is described by an initial Auxin flux from a source to a sink that is gradually channelized into cells with high levels of highly polarized transporters. The proposed model simulates a wide range of leaf forms, from simple shapes to lobed leaves. In the fifth paper, Kun Qian, Xiaosong Yang, and Jian J Zhang, Bournemouth University, UK, and Junxuan Bai and Junjun Pan, Beihang University, China, propose a set of tailored key technologies for laparoscopic surgery simulation, ranging from the simulation of soft tissues with different properties, the interactions between surgical tools and soft tissues, and the rendering of complex anatomical environment. Compared with the current methods, their tailored algorithms aimed at improving the performance from accuracy, stability, and efficiency perspectives. The authors also abstract and design a set of intuitive parameters that can provide developers with high flexibility to develop their own simulators. Finally, Dele Cui, Yun Sheng, and Guixu Zhang, East China Normal University, Shanghai, China, present an image-based method to simulate the traditional embroidery art. The method combines stroke-based rendering techniques with the Phong lighting model to create picturesque embroidery-like images. They first build a 3D stitch model and derive some most commonly used stitch patterns from it. Then they preprocess the input image by segmenting it into regions, from which the parameters to specify stitch patterns are obtained. Finally, they apply stitches back onto the desired regions and render them under a virtual light source. Experimental results show that their method, different from the existing schemes, is capable of performing fine embroidery simulations with the effects of lighting and shading based on an input image.

This issue contains six papers. In the first paper, Hui Liang, Jian Chang, and Shujie Deng, from the National Centre for Computer Animation in Bournemouth, UK; Can Chen from Changzhou University, China; Ruo-feng Tong, from Zhejiang University, Hangzhou, China; and Jian J. Zhang, from Bournemouth University, UK, design an immersive storytelling environment that allows multiple players to use naturally interactive hand gestures to manipulate virtual puppetry for assisting narration. A set of multimodal interaction techniques is presented for a hybrid user interface that integrates existing 3D visualization and interaction devices including head-mounted displays and depth motion sensor. In the second paper, Sybren A. Stüvel, Frank van der Stappen, and Arjan Egges, from Universiteit Utrecht, The Netherlands, present an investigation into the accuracy of human observers with regard to the recognition of collisions between virtual characters. They show the result of two user studies, where participants classify scenarios as “colliding” or “not colliding”; a pilot study investigates the perception of static images, whereas the main study expands on this by employing animated videos. In the pilot experiment, they investigated the effect of two variables on the ability to recognise collisions: distance between the character meshes, and visibility of the inter-character gap. In the main experiment, they investigate the angle between the character paths and the severity of the (near) collision. In the third paper, Marios Andreas Kyriakou, from the University of Cyprus; Xueni Pan, from the University of London, UK; and Yiorgos Lambros Chrysanthou, from the University of Cyprus examine attributes of virtual human behavior that may increase the plausibility of a simulated crowd and affect the user's experience in Virtual Reality (VR). Purpose-developed experiments in both Immersive and semi-Immersive VR systems queried the impact of collision and basic interaction between real users and the virtual crowd and their effect on the apparent realism and ease of navigation within VR. Participants' behavior and subjective measurements indicated that facilitating collision avoidance between the user and the virtual crowd makes the virtual characters, the environment, and the whole VR system appear more realistic and lifelike. In the fourth paper, Mihai Polceanu and Cedric Buche, from Florida International University, and Lab-STICC - ENIB, CERV, Plouzané, France, introduce a study of existing approaches that explicitly use mental simulation. Current implementations of the mental simulation paradigm, taken together, computationally address many aspects suggested by cognitive science research. Agents are able to find solutions to nontrivial scenarios in virtual or physical environments. Existing systems also learn new behavior by imitation of others similar to them and model the behavior of different others with the help of specialized models, culminating with the collaboration between agents and humans. Approaches that use self models are able to mentally simulate interaction and to learn about their own physical properties. In the fifth paper, Yuxing Qiu, Lipeng Yang, Shuai Li, and Qing Xia, from Beihang University, Beijing, China; Hong Qin, from Stony Brook University, USA; and Aimin Hao, from Beihang University, Beijing, China, advocate a method for the modeling and enhancement of scale-sensitive fluid details. The core of their method is the coupling of multilayer depth regression analysis and FLIP fluid simulation. First, they capture the depth buffer of the fluid surface from the top of scene. Second, they employ depth peeling to decompose the target fluid volume into multiple layers and conduct time–space analysis over surface layers. Third, they propose a logistic regression-based model to pinpoint the interacting regions, wherein multiple detail-relevant factors are taken into account. Finally, details are enhanced by animating extra diffuse materials and augmenting the air–fluid mixing phenomenon. Abdullah Bulbul, from Yildirim Beyazit Universitesi, Ankara, Turkey, and Rozenn Dahyot, from Trinity College, Dublin, Ireland, propose to automatically populate geo-located virtual cities by harvesting and analyzing online contents shared on social networks and websites. They show how pose and motion paths of agents can be realistically rendered using information gathered from social media. 3D cities are automatically generated using open source information available online. To provide a final rendering of both static and dynamic urban scenes, they use Unreal game engine.

from the University of Zaragoza, Spain, propose a "dynamic agent" endowed with a sensing device, a controller, and actuators to interact with the environment.The control architecture is based on ordinary differential equations with the function of modulating the stimulus signals to action signals under a sensory-motor flow.The parameter values are defined in an evolutionary process depending on the task to be performed.A series of experiments are presented to illustrate certain qualities of their model such as the adaptability to change, a highly intuitive and flexible design methodology, and a high degree of individual autonomy.

An accurate and efficient clothoid approximation approach is presented in this paper using Bézier curves based on the minimization of curvature profile difference. Compared with existing methods, the proposed approach is able to guarantee higher order geometric continuity with smaller approximation error in terms of position, orientation, and curvature. The approximation scheme takes place in three stages. First, a subset of clothoids with specific winding angle constraints referred to as elementary clothoids is approximated using quintic Bézier curves. Then, a basic clothoid defined in the first quadrant is formulated, which is composed of a series of transformed elementary clothoids. An adaptive sampling stra-tegy is applied to ensure that the resulting Bézier segments are computed within a specified accuracy and all the required information can be obtained offline and stored in a lookup table. Finally, a general clothoid with arbitrary parameters can be conveniently approximated based on the lookup table through appropriate geometric transformations. A comparison with the recent circular interpolation and rational Bézier curve based approximation shows that the proposed approach is able to achieve equivalent or greater computational efficiency in most scenarios.

We present a novel dense crowd simulation method. In real crowds of high density, people manoeuvring the crowd need to twist their torso to pass between others. Our proposed method does not use the traditional disc-shaped agent, but instead employs capsule-shaped agents, which enables us to plan such torso orientations. Contrary to other crowd simulation systems, which often focus on the movement of the entire crowd, our method distinguishes between active agents that try to manoeuvre through the crowd, and passive agents that have no incentive to move. We introduce the concept of a focus point to influence crowd agent orientation. Recorded data from real human crowds are used for validation, which shows that our proposed model produces equivalent paths for 85 percent of the validation set. Furthermore, we present a character animation technique that uses the results from our crowd model to generate torso-twisting and side-stepping characters.

Humans are not rational beings. Deviations from rationality in human thinking are currently well documented [25] as non-reducible to rational pursuit of egoistic benefit or its occasional distortion with temporary emotional excitation, as it is often assumed. This occurs not only outside conceptual reasoning or rational goal realization but also subconsciously and often in certainty that they did not and could not take place 'in my case'. Non-rationality can no longer be perceived as a rare affective abnormality in otherwise rational thinking, but as a systemic, permanent quality, 'a design feature' of human cognition. While social psychology has systematically addressed non-rationality of human cognition (including its non-emotional aspects) for decades [63]. It is not the case for computer science, despite obvious relevance for individual and group behavior modeling. This paper proposes brief survey of work in computational disciplines related to human-like non-rationality modeling including: Social Signal Processing, Cognitive Architectures, Affective Computing, Human-Like Agents and Normative Multi-agent Systems. It attempts to establish a common terminology and conceptual frame for this extremely interdisciplinary issue, reveal assumptions about non-rationality underlying the discussed models and disciplines, their current limitations and potential in contributing to solution. Finally, it also presents ideas concerning possible directions of development, hopefully contributing to solution of this challenging issue.

This paper presents an immersive volleyball game, where a player plays not only against virtual opponents but also with support on his/her side of virtual teammates. This volleyball game has been implemented for several 3D displays such as a stereoscopic display, an autostereoscopic display, Oculus Rift glasses, and a 320o Immersive Room. In this paper, we also propose a user study of the relations between virtual humans and the sense of presence in the different 3D displays. We particularly study how surrounding virtual humans affect the sense of presence. Results show that users more significantly perceived spatial presence of virtual environment and social presence of virtual humans with the Oculus Rift and the Immersive Room.

Articulated hand pose estimation plays an important role in human-computer interaction. Despite the recent progress, the accuracy of existing methods is still not satisfactory, partially due to the difficulty of embedded high-dimensional and non-linear regression problem. Different from the existing discriminative methods that regress for the hand pose with a single depth image, we propose to first project the query depth image onto three orthogonal planes and utilize these multi-view projections to regress for 2D heat-maps which estimate the joint positions on each plane. These multi-view heat-maps are then fused to produce final 3D hand pose estimation with learned pose priors. Experiments show that the proposed method largely outperforms state-of-the-art on a challenging dataset. Moreover, a cross-dataset experiment also demonstrates the good generalization ability of the proposed method.

Negative symptoms in schizophrenia are associated with significant burden and functional impairment, especially speech production. In clinical practice today, there are no robust treatments for negative symptoms and one obstacle surrounding its research is the lack of an objective measure. To this end, we explore non-verbal speech cues as objective measures. Specifically, we extract these cues while schizophrenic patients are interviewed by psychologists. We have analyzed interviews of 15 patients who were enrolled in an observational study on the effectiveness of Cognitive Remediation Therapy (CRT). The subject (undergoing CRT) and control group (not undergoing CRT) contains 8 and 7 individuals respectively. The patients were recorded during three sessions while being evaluated for negative symptoms over a 12-week follow-up period. In order to validate the non-verbal speech cues, we computed their correlation with the Negative Symptom Assessment (NSA-16). Our results suggest a strong correlation between certain measures of the two rating sets. Supervised prediction of the subjective ratings from the non-verbal speech features with leave-one-person-out cross-validation has reasonable accuracy of 53-80%. Furthermore, the non-verbal cues can be used to reliably distinguish between the subjects and controls, as supervised learning methods can classify the two groups with 80-93% accuracy.

Abstract This paper presents a semi‐automatic method of parameterizing an existing social context cognition model. It discusses benefits of the social context cognition models for example in personality modeling and their key issue that is parametrization. It briefly introduces social context cognition model and describes a new method of its crowd‐sourcing‐based parametrization. Later, validation is provided, and ability to recreate social context cognition in the provided samples is presented with good generalization for the unknown cases. Finally, model's stability for the continuous stream of dynamic social context input data is shown. Presented system contributes to the believable agent modeling and social simulations by making much needed applications of social context cognition models easier by addressing the so far unsolved troublesome parametrization issues. Copyright © 2016 John Wiley & Sons, Ltd.

This issue contains four papers. In the first paper, Mingfei Wang, Jinyuan Jia, Ning Xie, and Chenxi Zhang, from Tongji University in Shanghai, China, aim to solve the challenging problems of choosing the data supplier for data-dispatching services in distributed virtual environments based on peer-to-peer networks. They propose a dynamic node-organizing mechanism that aims by applying the avatar's behavioral characteristics to the neighbor maintenance mechanism and scene data transmission. They have conducted extensive simulation experiments that simulate avatar behaviors in a popular online game. The results show that their proposed mechanism achieved a substantial alleviation of neighbor churn and reduced information exchange, which improves the transmission efficiency in DVEs. In the second paper, Masaki Oshita, from the Kyushu Institute of Technology, Japan, proposes an interactive character motion control interface that uses hands. Using their hands and fingers, the user can control a large number of degrees of freedom (DOFs) at the same time. The author applied principal component analysis (PCA) to a set of sample poses and assigned the extracted principal components to each DOF of the hands (such as the hand positions and finger bending/extending angles). The author developed methods for computing the feature vector, for applying PCA, and for pose and action synthesis. In addition, he introduced a pose transition method for performing a step motion when necessary to prevent foot sliding. He presents his experimental results and demonstrates the effectiveness of his interface. In the third paper, Wenwu Yang, Xun Wang, Wangbin Kou, Bailin Yang, and Guozheng Wang, from Zhejiang Gongshang University, Hangzhou, China, present a topology-aware method based on moving least squares (MLS) deformation approach for 2D characters. First, a Laplace equation is solved to obtain a set of weights, which are called as harmonic weights. Then, the MLS deformation is performed by using the harmonic weights as the deformation influence of the user-specified controls. Finally, the possible distortion in the traditional MLS deformation can be effectively avoided, since the harmonic weights spread the deformation of the controls in a localized and topology-aware way. In addition, a simple but effective area-preserving variant of MLS deformation is proposed, which is suitable for the editing of incompressible objects. Mohammadali Hajizadeh and Hossein Ebrahimnezhad, from Sahand University of Technology, Islamic Republic of Iran, propose a key frame-based technique for 3D dynamic mesh compression. First, key frames are extracted from the animated sequence. Extracted key frames are then linearly combined using blending weights to predict the vertex locations of the other frames. These blending weights play a key role in the proposed algorithm since the prediction performance and the required number of key frames are greatly dependent on these weights. They present a novel method in order to compute the optimum blending weight, which makes it possible to predict location of the vertices of the non-key frames with the minimum number of key frames. The residual prediction errors are finally quantized and encoded using Huffman coding and another heuristic method. Experimental results on different test sequences with various sizes, topologies, and geometries demonstrate the privileged performance of the proposed method compared to the previous techniques.

Articulated hand pose recovery in egocentric vision is useful for in-air interaction with the wearable devices, such as the Google glasses. Despite the progress obtained with the depth camera, this task is still challenging with ordinary RGB cameras. In this paper we demonstrate the possibility to recover both the articulated hand pose and its distance from the camera with a single RGB camera in egocentric view. We address this problem by modeling the distance as a hidden variable and use the Conditional Regression Forest to infer the pose and distance jointly. Especially, we find that the pose estimation accuracy can be further enhanced by incorporating the hand part semantics. The experimental results show that the proposed method achieves good performance on both a synthesized dataset and several real-world color image sequences that are captured in different environments. In addition, our system runs in real-time at more than 10fps.

The goal of Image Quality Assessment (IQA) is to design computational models that can automatically predict the perceived image quality consistent with human subjective ratings. In this paper, we propose a full reference IQA metric gradient weighted structural similarity (GW-SSIM) by incorporating the gradient information to the well-known IQA metric SSIM. Experimental results demonstrate that GW-SSIM can greatly improve the quality prediction accuracy and achieve the best performance among the SSIM-based methods by addressing SSIM's shortcomings. Additionally, incorporating the proposed gradient weighting (GW) map into peak-signal-to-noise ratio (PSNR) also makes it quite competitive to state-of-the-art IQA models, and this is meaningful since PSNR is still a widely adopted metric.

Wearable devices such as Microsoft Hololens and Google glass are highly popular in recent years. As traditional input hardware is difficult to use on such platforms, vision-based hand pose tracking and gesture control techniques are more suitable alternatives. This demo shows the possibility to interact with 3D contents with bare hands on wearable devices by two Augmented Reality applications, including virtual teapot manipulation and fountain animation in hand. Technically, we use a head-mounted depth camera to capture the RGB-D images from egocentric view, and adopt the random forest to regress for the palm pose and classify the hand gesture simultaneously via a spatial-voting framework. The predicted pose and gesture are used to render the 3D virtual objects, which are overlaid onto the hand region in input RGB images with camera calibration parameters for seamless virtual and real scene synthesis.

Abstract Expanding the spectrum of agent social capabilities is an important challenge in agent‐based simulation and other domains. While human‐like emotionality has been vastly explored in the last 20years, little research addresses explicit, psychologically believable social situation modeling. Recently, some important elements have been underlined: hybrid connectionist models outside formal ontologies; complex subjective representations linking culture, personality and norms, and so on, but proposed solutions do not provide a formalized structure of a social experience, expressive and well‐grounded in psychology. In this paper, we develop a new approach to social situation modeling based on the dramaturgical and dissonance theories. A new component (Dramaturgical Module) is described with implementation used to generate example behavior depicting new social modeling capabilities and a believable representation of the relevant psychological theories. We present a case scenario with a dramaturgical interpretation of dynamic social situations and related cognitive dissonances resulting in a simple and flexible classification. Easily usable in reasoning, planning or affect generation, dramaturgical interpretation is additionally presented here as basis of social affect generation. Copyright © 2015 John Wiley & Sons, Ltd.

first paper, Changbo Wang, Qiang Zhang, and Fanlong Kong, from East China Normal University in Shanghai, China, present a highly effective method of modeling and animating debris flows with adaptive grid.The debris flow is modeled as Bingham plastic fluid with view-dependent adaptive grid to model the flow volume, and the boundless grids can cover the large scale region of debris flow.Then the mixed grids are built for confluent flows, and two-way coupling interaction between flows and environment is considered.After extracting the debris flow surface, adaptive surface tension combining wave particles equation is used to enhance the details, and sprays are generated by particles considering the interaction between two fluid volumes.

and Nathan Sturtevant from the

The positions of the hand joints are important high-level features for hand-based human-computer interaction. We present a novel method to predict the 3-D joint positions from the depth images and the parsed hand parts obtained with a pretrained classifier. The hand parts are utilized as the additional cue to resolve the multimodal predictions produced by the previous regression-based method without increasing the computational cost significantly. In addition, we further enforce the hand motion constraints to fuse the per-pixel prediction results. The posterior distribution of the joints is formulated as a weighted product of experts model based on the individual pixel predictions, which is maximized via the expectation-maximization algorithm on a learned low-dimensional space of the hand joint parameters. The experimental results show the proposed method improves the prediction accuracy considerably compared with the rivals that also regress for the joint locations from the depth images. Especially, we show that the regressor learned on synthesized dataset also gives accurate prediction on real-world depth images by enforcing the hand part correlations despite their discrepancies.

Trust is one source of information that has been widely adopted to personalize online services for users, such as in product recommendations. However, trust information is usually very sparse or unavailable for most online systems. To narrow this gap, we propose a principled approach that predicts implicit trust from users' interactions, by extending a well-known trust antecedents framework. Specifically, we consider both local and global trustworthiness of target users, and form a personalized trust metric by further taking into account the active user's propensity to trust. Experimental results on two real-world datasets show that our approach works better than contemporary counterparts in terms of trust ranking performance when direct user interactions are limited.

demonstrate a pipeline where humanoid 3D models can be incorporated within seconds into an animation system and infused with a wide range of capabilities, such as locomotion, object manipulation, gazing, speech synthesis, and lip syncing.They offer a set of heuristics that can associate arbitrary joint names with canonical ones and describe a fast retargeting algorithm that enables them to instill a set of behaviors onto an arbitrary humanoid skeleton on-the-fly.In the second paper, Mika Tapani Rantanen, and Martti Juhola, from the University of Tampere, Finland, examine how a path-planning problem can be solved in changing environments using probabilistic roadmap planners.They show that probabilistic roadmaps can be built in such a way that they work with dynamic obstacles; but as their experiments show, the roadmap graph must be built carefully.They compare three different methods that are used to connect the nodes of the roadmap graph.One of these is a distance-based method, which they present in this paper.

ABSTRACT Simulating a crowded scene like a busy shopping street requires tight packing of virtual characters. In such cases, collisions are likely to occur, and the choice in collision detection shape will influence how characters are allowed to intermingle. Full collision detection is too expensive for crowds, so simplifications are needed. The most common simplification, the fixed‐width, pose‐independent cylinder, does not allow intermingling of characters, as it will either cause too much empty space between characters or undetected penetrations. As a possible solution to this problem, we introduce the bounding cylinder hierarchy (BCH), a bounding volume hierarchy that uses vertical cylinders as bounding shapes. Because the BCH is a generalization of the single cylinder, we expect that this representation can be easily integrated with existing crowd simulation systems. We compare our BCH with commonly used collision shapes, namely the single cylinder and oriented bounding box tree, in terms of query time, construction time, and represented volume. To get an indication of possible crowd densities, we investigate how close characters can be before collision is detected and finally propose a critical maximum depth for the BCH. Copyright © 2014 John Wiley & Sons, Ltd.

Hand pose tracking and gesture recognition are useful for human-computer interaction, while a major problem is the lack of discriminative features for compact hand representation. We present a robust hand parsing scheme to extract a high-level description of the hand from the depth image. A novel distance-adaptive selection method is proposed to get more discriminative depth-context features. Besides, we propose a Superpixel-Markov Random Field (SMRF) parsing scheme to enforce the spatial smoothness and the label co-occurrence prior to remove the misclassified regions. Compared to pixel-level filtering, the SMRF scheme is more suitable to model the misclassified regions. By fusing the temporal constraints, its performance can be further improved. Overall, the proposed hand parsing scheme is accurate and efficient. The tests on synthesized dataset show it gives much higher accuracy for single-frame parsing and enhanced robustness for continuous sequence parsing compared to benchmarks. The tests on real-world depth images of the hand and human body show the robustness to complex hand configurations of our method and its generalization power to different kinds of articulated objects.

Lack of motivation to provide ratings and eligibility to rate generally only after purchase restrain the effectiveness of recommender systems and contribute to the well-known data sparsity and cold start problems. This paper proposes a new information source for recommender systems, called prior ratings. Prior ratings are based on users' experiences of virtual products in a mediated environment, and they can be submitted prior to purchase. A conceptual model of prior ratings is proposed, integrating the environmental factor presence whose effects on product evaluation have not been studied previously. A user study conducted in website and virtual store modalities demonstrates the validity of the conceptual model, in that users are more willing and confident to provide prior ratings in virtual environments.

In this paper, a novel human-virtual human interaction system is proposed. This system supports a real human to communicate with a virtual human using natural body language. Meanwhile, the virtual human is capable of understanding the meaning of human upper body gestures and reacting with its own personality by the means of body action, facial expression and verbal language simultaneously. In total, 11 human upper body gestures with and without human-object interaction are currently involved in the system. They can be characterized by human head, hand and arm posture. In our system implementation, the wearable Immersion CyberGlove II is used to capture the hand posture and the vision-based Microsoft Kinect takes charge of capturing the head and arm posture. This is a new sensor solution for human-gesture capture, and can be regarded as the most important contribution of this paper. Based on the posture data from the CyberGlove II and the Kinect, an effective and real-time human gesture recognition algorithm is also proposed. To verify the effectiveness of the gesture recognition method, we build a human gesture sample dataset. Additionally, the experiments demonstrate that our algorithm can recognize human gestures with high accuracy in real time.

ABSTRACT In this paper, we propose a method to achieve effective facial emotional expressivity for embodied conversational agents by considering two types of asymmetry when exploiting the valence–arousal–dominance representation of emotions. Indeed, the asymmetry of facial expressions helps to convey complex emotional feelings such as conflicting and/or hidden emotions due to social conventions. To achieve such a higher degree of facial expression in a generic way, we propose a new model for mapping the valence–arousal–dominance emotion model onto a set of 12 scalar facial part actions built mostly by combining pairs of antagonist action units from the Facial Action Coding System. The proposed linear model can automatically drive a large number of autonomous virtual humans or support the interactive design of complex facial expressions over time. By design, our approach produces symmetric facial expressions, as expected for most of the emotional spectrum. However, more complex ambivalent feelings can be produced when differing emotions are applied on the left and right sides of the face. We conducted an experiment on static images produced by our approach to compare the expressive power of symmetric and asymmetric facial expressions for a set of eight basic and complex emotions. Results confirm both the pertinence of our general mapping for expressing basic emotions and the significant improvement brought by asymmetry for expressing ambivalent feelings. Copyright © 2013 John Wiley & Sons, Ltd.

This issue is a special issue with selected papers from Motion in Games (MIG) 2012, which was held during November 15–17 in Rennes, France. Five papers were selected by a review committee composed of Paul Kry, McGill University; Rachel McDonnell, Trinity College Dublin; and Arjan Egges, Utrecht University. The review committee took into account not only the manuscripts but also the presentations and the potential for impact on the motion in games area that is being nurtured by MIG. This special issue contains four out of the five selected papers. The fifth paper will appear in the next issue of Computer Animation & Virtual Worlds. The first paper on this issue is from Peter Sandilands, Myung Geol Choi and Taku Komura, from the University of Edinburgh, UK. The authors propose a technique for action motion capture that allows them to capture an object's motion and geometry alongside a character's movement and local environment, using a magnetic motion capture system and a RGB-D sensor. Traditional methods of actor motion capture do not give any information about the spatial relationship between objects you may interact with, or are limited to large props and motions that are not occluded during capture. The proposed method not only gives greater information when placing a character in the scene, but enables the authors to digitally recreate the scene in motion without significant animator work after capture. The second paper by Junghyun Ahn, Stephane Gobron, Daniel Thalmann, and Ronan Boulic, from Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, and NTU, Singapore, addresses emotional expressivity for embodied conversational agents by considering asymmetric facial expressions. The asymmetry of facial expressions helps to convey complex emotional feelings such as conflicting and/or hidden emotions due to social conventions. The proposed linear model can automatically drive a large number of autonomous virtual humans, or support the interactive design of complex facial expressions over time. The approach produces facial expressions for most of the emotional spectrum and it can also achieve more complex ambivalent feelings when differing emotions are applied on the left and right sides of the face. The third paper by Robert Backman and Marcelo Kallmann from the University of California, Merced, presents a system that allows non-programmers to create generic controllers for physically-simulated characters. The core of the proposed system is based on a directed acyclic graph of trajectory transformations, which can be modified by feedback terms and serve as reference motions tracked by the physically simulated character. The authors introduce tools to enable the automatic creation of robust and parameterized controllers suitable for running in real-time applications, such as in computer games. The entire process is accomplished by means of a graphical user interface. The paper demonstrates how the system can be intuitively used to design a simbicon-like walking controller and a parameterized jump controller to be used in real-time simulations. The last paper of this issue is by Jongmin Kim, Yeongho Seol and Jehee Lee, from the Seoul National University, Korea. The authors describe a real-time performance animation system that reproduces full-body character animation based on sparse 3D motion sensors on a performer. Producing faithful character animation from this setting is a mathematically ill-posed problem because input data from the sensors are not sufficient to determine the full degrees of freedom of a character. Given the input data from 3D motion sensors, similar poses are selected from a motion database and a local model is built for transforming on-line the low-dimensional input signal into a high-dimensional character pose. A regression method based on kernel CCA (Canonical Correlation Analysis) is employed and it effectively handles a wide variety of motions. Examples show that various human motions are naturally reproduced by the proposed method.

This issue contains five regular papers. Ahmad Abdul Karim, Thibaut Gaudin, Alexandre Meyer, Axel Buendia and Saïda Bouakaz, from Université Lyon 1 and Spir.Ops in France, present a fully procedural method capable of generating in real time a wide range of locomotion for multi-legged characters in a dynamic environment, without using any motion data. Their system consists of several independent blocks: a character controller, a gait/tempo manager, a 3D path constructor and a footprints planner. The four modules work cooperatively to calculate in real time the footprints and the 3D trajectories of the feet and the pelvis. The system can animate dozens of creatures using dedicated level of detail techniques and is totally controllable allowing the user to design a multitude of locomotion styles through a user-friendly interface. In the second paper, Amit Kumar and Aparajita Ojha, from PDPM Indian Institute of Information Technology in Jabalpur, in India, propose a new approach to natural path planning by adding wavelet noise to a path generated using subdivision-based corridor map method. Because wavelet noise is almost perfectly band-limited and provides good details with minimal aliasing effects, the resulting path becomes smoother and more natural. Moreover, by appropriately choosing the levels of down/up sampling in the wavelet noise generation algorithm, frequency of wavelet noise can be adjusted. This serves as an effective tool in bringing variations in path as per the requirement. The third paper by Yanzhen Wang, Yueshan Xiong, Kai Xu and Dong Liu, from National University of Defense Technology in Changsha, Hunan, in China, describes a surgical procedure simulation system for the training of arthroscopic ACL reconstruction involving operations such as puncturing, probing, incision and drilling. In this system, the authors employ a linear elastic finite element method and position-based dynamics for deformable modelling. Simplified vertex duplicating method and an implementation of real-time Boolean operations are proposed for the topological change of tissue models involved in the incision simulation and tunnel construction. Two specially designed force-feedback models are introduced for the haptic rendering of probing and drilling operations. In the fourth paper by Siddharth Hegde, Christos Gatzidis and Feng Tian, from Bournemouth University, in UK, look at the different methods presented over the past few decades that attempted to recreate digital paintings. Whereas previous surveys concentrate on the broader subject of non-photorealistic rendering, the focus of this paper is firmly placed on painterly rendering techniques. The authors compare different methods used to produce different output painting styles such as abstract, colour pencil, watercolour, oriental, oil and pastel. Although some methods demand a high level of interaction using a skilled artist, others require simple parameters provided by a user with little or no artistic experience. The last paper by Llyr ap Cenydd and Bill Teahan, from Bangor University, in UK, describes a system for dynamically animating the locomotive behaviour of arthropods in real time, facilitating realistic and autonomous traversal across an arbitrary environment. By combining a de-centralized reactive behavioural model with a hybrid approach to motion that utilizes the comparative advantages of physical simulation and kinematic control, the system is capable of automatically generating complex organic motion over a wide range of surface features, independent of structural complexity. The reactive embodiment of the creature, combined with the physical simulation of the virtual world enables emergent behaviours to form that are entirely based on circumstance, including rigid-body interaction, grip recovery and adaptive wall climbing.

This special issue contains 28 papers selected from the Computer Animation and Social Agents 2013 (CASA'2013) Conference. This conference was founded by the Computer Graphics Society in 1988 in Geneva and has, since then, been held in various countries around the world, 2011 in China, last year in Singapore, this year in Istanbul, Turkey, and next year in Houston, USA. The 3-day conference features more than 55 speakers who present their most current research in the areas of computer animation, autonomous social robots and virtual humans, and how these technologies can be leveraged to advance related areas, such as music, virtual cities, and crowd control. Addressing this year's conference are human motion modeling expert associate professor Jinxiang Chai from Texas A&M University and renowned haptics researcher, associate professor Cagatay Basdogan of Koc University. This year, we received 141 full papers and selected only 28 of those for this special issue; meaning, an acceptance rate of only 20%. It is needless to say that these are of high quality, all having been reviewed by at least three reviewers. The themes are various, covering the entire international field of research in computer animation and virtual worlds and sorted by their sessions in the conference; they are as follows. Crowd Simulation, Fluid Simulation, Natural Phenomena and Lighting, Face/Hair Animation and Rendering, Virtual Cities and Path Planning, Paint Simulation, Medical/Immersive Applications, Virtual Agents, 3D Mesh Deformation, Human Action Recognition, 3D Mesh and Geometric Modeling, and Human Motion. We would like to thank the authors for having submitted a paper to CASA'2013 as well as the Program Committee members, the external reviewers, and all the people who have contributed to the success of CASA 2013 in Istanbul. Nadia Magnenat-Thalmann Mustafa Kasap Daniel Thalmann Tolga Capin Selim Balcisoy Tolga Eren Norman Badler Selim Balcisoy Ronan Boulic Yiyu Cai Tolga Capin Marc Cavazza Bing-Yu Chen Yiorgos Chrysanthou Sabine Coquillart Frederic Cordier Justin Dauwels Etienne De-Sevin Zhi-Gang Deng Fabian Di Fiore Yves Duthen Arjan Egges Abdennour El Rhalibi Petros Faloutsos Ugur Gudukbay Mario Gutierrez James Hahn Ying He Shi-Min Hu Zhiyong Huang Veysi Isler Jean-Pierre Jessel Sophie Joerg Chris Joslin Prem Kalra Mustafa Kasap Scott King Taku Komura Caroline Larboulette Rynson Lau Wonsook Lee Tsai-Yen Li Ming Lin Anderson Maciel Nadia Magnenat Thalmann Dinesh Manocha Rachel Mcdonnell Franck Multon Soraia Musse Junyong Noh Igor Pandzic George Papagiannakis Laura Papaleo Nuria Pelechano Christopher Peters Julien Pettre Flavien Picon Tiberiu Popa Nicolas Pronost Isaac Rudomin Hyewon Seo Hubert Shum Matthias Teschner Daniel Thalmann Xin Tong Andy W. H. Khong Huamin Wang Jun Wang Enhua Wu Junsong Yuan Cem Yuksel Zerrin Yumak Jian Zhang Zhengyou Zhang Jianmin Zheng

We present a vision-based approach for robust 3D fingertip and palm tracking on depth images using a single Kinect sensor. First the hand is segmented in the depth images by applying depth and morphological constraints. The palm is located by performing distance transform to the hand contour and tracked with a Kalman filter. The fingertips are detected by combining three depth-based features and tracked with a particle filter over successive frames. Quantitative results on synthetic depth sequences show the proposed scheme can track the fingertips quite accurately. Besides, its capabilities are further demonstrated through a real-life human-computer interaction application.

This paper presents an interactive dynamic controller used to generate locomotion patterns for humanoid robots. The purpose of this work is to provide animators and artists easy and intuitive tools to design expressive motions for humanoid robots. A review of similar work in the computer animation community has guided our choices regarding the implementation and level of interaction between the user and an inverse dynamics solver. We have used our controller on a model of the Aldebaran humanoid robot Nao, and have generated a few expressive locomotion patterns that are presented in the experimental section of this paper.

ABSTRACT Traversing dense crowds can be challenging, but it is especially difficult in a virtual environment where the user is limited to simple input devices. Predicting near‐future user movements with a hidden Markov model allows nearby autonomous agents to react politely, that is, to specifically avoid impeding the movement of the user. This predictive model and simple avoidance scheme are tested by six subjects in 360 short interactive games and by a 10‐participant two‐alternative forced choice questionnaire. Polite agents are found to significantly improve the player's ability to navigate quickly and without collision, and the resulting character movements showed increased naturalness for two of the three game scenarios. Copyright © 2012 John Wiley & Sons, Ltd.

In the first paper, proposed by Cihan Halit and Tolga Capin from Bilkent University in Turkey, an automatic approach to extract key frames from a motion capture sequence is proposed.The input sequence is treated as motion curves to obtain a "motion saliency."With this approach, around 8% of the frames are selected to be key frames for motion capture sequences.The next paper on feature sensitive deformation for triangular mesh models comes from Shandong University in China.The four co-authors propose a novel surface deformation method based on a feature sensitive (FS) metric.Examples are included to show that the feature sensitive deformation method better preserves mesh details, especially features, than in existing Laplacian methods.The third paper co-authored by Andreas Alexandros Vasilakis and Ioannis Fudos from the University of Ioannina in Greece proposes a GPU skinning based method based on a refined skeletonization.To avoid the artifacts generated in previous skinning approaches and the associated high training costs, the authors have developed an efficient and robust rigid skinning technique that applies blending patches around joints.To achieve real time animation, they have adapted all steps of their rigid skinning algorithm so that they are performed efficiently on the GPU.

2011 in Chengdu, China.The last two papers are regular papers.In the first paper, Min Meng, Lubin Fan and Ligang Liu from Zhejiang University, in Hangzhou, China, present a novel sketch-based tool, called iCutter (short for Intelligent Cutter), for cutting out semantic parts of 3D shapes.When a user performs a cutting task, he or she only needs to draw a freehand stroke to roughly specify where cuts should be made without much attention.Then iCutter intelligently returns the best cut that meets the user's intention and expectation.The authors demonstrate various examples to illustrate the flexibility and applicability of their iCutter tool.Inmaculada Rodriguez and Anna Puig from the University of Barcelona and Marc Esteva from the Autonomous University of Barcelona, in Spain, propose, in the third paper, a generic interaction framework, which controls intelligent objects' actions in different virtual world platforms.These actions are based on the state of external platform-independent AI-based systems such as multiagent and rule-based systems.The authors have evaluated the proposed framework by means of two intelligent objects, a door and a notice board, incorporating them in Second Life and OpenWonderland virtual worlds.These objects allow to work along three advanced aspects of a serious virtual environment.

This issue contains six papers. In the first paper, Changbo Wang, Chenhui Li, Jinqiu Dai, and Yang Li, from East China Normal University in Shanghai, China, present a new rendering method based on adaptive lattice for lighting participating media of translucent materials such as marble, wax, and shaft light. Firstly, multi-scale hierarchical lattice is constructed. Then, an adaptive method to trace diffuse photons and marked specular photons with different phase functions is suggested. Multiple lights and heterogeneous materials are also considered here. Further, the mixed rendering method and GPU accelerate technology are introduced to render different light effects under different participating media. Yijiang Zhang, Julien Pettré, Jan Ondrej, Xueying Qin, Qunsheng Peng, and Stéphane Donikian from Zhejiang University in Hangzhou, China and IRISA in Rennes, France, propose, in the second paper, a video-based mixed reality system enabling interaction between real and virtual humans in real scenes. The real scene is captured by a camera, and the evolution of the environment is obtained by video analysis, which provides the constraint for the motion of virtual characters. Next, the virtual characters are modeled to move around the scene, keeping away from real obstacles and other virtual characters. To seamlessly integrate the virtual characters, the alpha map of each real pedestrian is carefully extracted. In the third paper, Jong-Hyuk Kim and Jung-Ju Choi from Ajou University in Suwon, Korea, and Christoph M. Hoffmann from Purdue University in USA propose a method to parameterize the skin deformation by skeletal motion. They present skin deformation by multiplication of two matrices, one of which encodes the basis matrix that deformation takes place and the other does the time-varying signals that capture the virtual muscle action. The time-varying signals are then parameterized by joint angles using RBF, which provides a fast and intuitive way to control the skin deformation. Furthermore, given a set of two skin deformations, they capture the style between the deformations and transfer the style into another deformation data by using only matrix computations. The fourth paper by Jianping Hu and Qi Xie from Northeast Dianli University, in Jilin, China, and Xiuping Liu from Dalian University of Technology in China present a subdivision connectivity remeshing approach. The main contribution lies in adopting a low distortion spherical parameterization approach to generate high-quality subdivision connectivity meshes. Besides, a simple and efficient point location method on the sphere based on the uniform partition of the rectangle is presented, which is used to find the containing triangle in the spherical mesh for each point on the sphere rapidly. The method can generate high-quality subdivision connectivity meshes fast, which can be applied to level of detail and progressive transmission. In the fifth paper, Kyusung Cho, Jinki Jung, Sang-Wook Lee, Sang Ok Lim, and Hyun Seung Yang from KAIST in Daejeon, Korea, present a markerless tracking method for augmented reality books, which recognizes and tracks a large number of pages in real-time, even on PCs with low computation power. For fast recognition with respect to a large number of pages, they propose a generic randomized forest. They also define the spatial locality of the subregions in an image to resolve the problem of a dropping recognition rate under a complex background. For tracking with minimal jittering, they propose the adaptive keyframe-based tracking method, which automatically updates the current frame as a keyframe when it describes the page better than the existing one. The last paper by Erdem Akagunduz, Ilkay Ulusoy, and Murat Yirci from Middle East Technical University in Turkey presents a new dynamic volume spline model for human face skin. The performance of the model is discussed on the basis of the estimation of the results of facial surgery of three different patients. Face models of the patients are obtained from 3D CT/MR scans by segmenting the skull, muscle, and skin layers. The control points of the dynamic volume spline are localized masses with viscoelastic material properties. These parameters are computed from the skin material properties that were published in the literature. Once the face models are generated, facial surgery plannings are simulated.

THIS special section is dedicated to the three Best Papers of VRST 2009, which was held in Kyoto, Japan from 18 to 20 November 2009. The papers were first selected by a jury based on the referees’ reports and the oral presentation. The authors were then asked to provide an extended version. The extended papers were then reviewed through a strict peer review process. The first paper, “Robust Relocalization and Its Evaluation for Online Environment Map Construction” by Sehwan Kim, Christopher Coffin, and Tobias Hollerer from the University of California in Santa Barbara, presents robust methodology and evaluation for camera orientation relocalization, using virtual keyframes for online environment map construction. In case of tracking loss, incoming camera frames are matched against known-orientation keyframes to reestimate camera orientation. Instead of solely using real keyframes from incoming video, the proposed approach employs virtual keyframes which are distributed strategically within completed portions of an environment map. The authors compare different system variants using three evaluation methods to show that the proposed system is useful in a practical sense. To improve recovery robustness against lighting changes in indoor and outdoor environments, they propose a new approach based on illumination normalization and saturated area removal. In the second paper, “Natural Perspective Projections for Head-Mounted Displays,” Frank Steinicke, Gerd Bruder, Scott Kuhl, Pete Willemsen, Markus Lappe, and Klaus H. Hinrichs from Munster University in Germany analyze the user’s perception of a virtual environment displayed in a Head Mounted Displayed (HMD), which is rendered with different geometric fields of views. They introduce a psychophysical calibration method to determine the HMD’s actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects—even if these perspectives deviate from the perspectives that are inherently defined by the display field of view. In the third paper, “A Wide-View Parallax-Free EyeMark Recorder with a Hyperboloidal Half-Silvered Mirror and Appearance-Based Gaze Estimation,” Hiroki Mori, Erika Sumiya, Tomohiro Mashita, Kiyoshi Kiyokawa, and Haruo Takemura from Osaka University propose a wideview parallax-free eye-mark recorder with a hyperboloidal half-silvered mirror and a gaze estimation method suitable for the device. Their eye-mark recorder provides a wide field-of-view video recording of the user’s exact view by positioning the focal point of the mirror at the user’s viewpoint. They implemented and evaluated a gaze estimation method for their eye-mark recorder. They apply principal component analysis and multiple regression analysis to determine the relationship between the captured images and their corresponding gaze points.

Digital media are more and more present in our lives, but we are still waiting for interfaces and devices completely adapted to this content. In this paper, we present the virtual shelf, an application dedicated to interact with our digital music collection. Our concept is to visualize our music collection in a familiar environment, a classic CD shelf, and to interact with it in a natural way, using the well-known drag-and-drop paradigm: you can drop an album in your friend's shelf to automatically add it to his/her personal music collection, or you can drop it on a close sound player in order to play the selected album on this device.

In this paper, we present a fuzzy mechanism to update in a more natural way the emotional and mood states of virtual humans. To implement this mechanism, we take into account the ten personality scales defined by Minnesota Multiphasic Personality Inventory to endow virtual humans with a real personality. In this manner, we apply different sets of fuzzy rules to change and regulate the affective state of virtual humans according to their personality, emotional and mood history, and the level of intensity of events they perceive from their environment.

Our goal is to create dancing crowds in cyber worlds and to use this feature to support creative endeavors such as pre-visualization of choreography and actual stage performances. In this paper we present a method of motion planning using dance motion clips. We describe a trial algorithm of collision avoidance using a grid map. We also present methods to create variety in animation for dance choreographies. As a result, we confirmed that most collisions could be avoided by the motion planning method. However, the need for some improvements in creating a conceptual dancing crowd was found.

This volume of Computer Animation and Virtual Worlds (CAVW) contains a selection of papers submitted to CASA 2010, the 23rd International Conference on Computer Animation and Social Agents. CASA is one of the premier international conferences in the field of computer animation and social agents, organized under the auspices of the Computer Graphics Society (CGS). It has been founded in 1988, and, over the last years, it has been organized in Europe: Geneva (2002, 2004, 2006), Hasselt (2007), Amsterdam (2009); in USA: Philadelphia (1998, 2000), New Jersey (2003); and in Asia: Seoul (2001, 2008), Hong Kong (2005). This year, CASA 2010 was organized in Saint-Malo, France from the 30th of May to the 2nd of June 2010. The organization was done by Bunraku, an INRIA Project-team in common with CNRS, INSA of Rennes, University of Rennes 1, and Ecole Normale Supérieure de Cachan. The CASA 2010 edition received 104 submissions from 27 countries and 6 continents. Each submission received at least 3 reviews and 32 among them were selected to appear in this special issue of Computer Animation and Virtual Worlds. We thank all the authors who have submitted their work to this conference allowing us to present this nice and diversified program. We thank also the International Program Committee members and the additional external reviewers for the time and energy they have invested in the reviewing process. A particular thank goes to the INRIA conference support team, especially to Edith Blin-Guyot and Steeve Tessier, for their support in organizing the conference, taking care of financial, material, and organizational matters. CASA 2010 has been sponsored by INRIA, by the IRIS European Network of Excellence (Integrating Research in Interactive Storytelling), by GDR IG (Groupement de Recherche Informatique Graphique), by Fondation Michel Métivier, by the Brittany Regional Council, by the University of Rennes 1, by the Ecole Normale Supérieure de Cachan, and by the Biometrics Company. The 32 papers presented in this special issue are divided into several categories: Cartoon and Sketch-based animation techniques, Stylized animation, Deformable models, Meshes, Physically based animation, Motion Analysis and Synthesis, Steering and Crowds, Facial expression, Social Agents, and finally Augmented Reality.

This issue contains four regular papers. The first paper, by Qingqiong Deng and Xiaopeng Zhang from the CAS Institute of Automation in China, Gang Yang from the Beijing Forestry University, and Marc Jaeger from the INRIA Saclay in Montpellier, France present a new foliage simplification framework for level of detail (LOD) of plant geometric models and forest rendering. Leaf density is introduced to adapt compression to the local distribution of leaves, so that more visually relevant details are kept. With a specific design of LOD storage structure, the costly hierarchical traversal of a binary tree is replaced by simple linear lookup array retrieval. This structure is GPU-oriented and decreases the communication between the CPU and the GPU for LOD level model loading in rendering. Sun-Uk Hwang, Beom-Chan Lee, Jeha Ryu, Kwan H. Lee, and Yong-Gu Lee from GIST-Mechatronics in Korea propose a temporal smoothing technique for haptic interaction using a sensing glove in multi-modal applications. The technique employs two processes: (1) a noise reduction method to reduce jitter noise at the sensors in the sensing glove, and (2) an adaptive force extrapolation for time-varying haptic and video frame rates. The authors have developed a test platform to assess a simple box model and relatively complex models such as gamephone, portable media player. The third paper, by Nicolas Stoiber from Orange Laboratory in France, Renaud Seguier from Supelec, and Gaspard Breton from Orange Laboratory present an animation system that gathers the advantages of two approaches in animation: parameter-based animation and performance-based animation. By analyzing a database of facial motion, the authors create the human appearance space, which provides a coherent and continuous parameterization of human facial movements, while encapsulating the coherence of real facial deformations. The method optimally constructs an analogous appearance face for a synthetic character. In the fourth paper, I-Chen Lin, Wen-Hsing Chang, Yung-Sheng Lo, Jen-Yu Peng, and Chan-Yu Lin also from the National Chiao Tung University in Taiwan introduce, in the last paper, a novel optimization framework for estimating the static or dynamic surfaces with details. The proposed method uses dense depths from a structured-light system or sparse ones from motion capture as the initial positions, and exploits non-Lambertian reflectance models to approximate surface reflectance. Multi-stage shape-from-shading is then applied to optimize both shape geometry and reflectance properties.

This contains five regular papers. The first paper, by Hui Chen and Hanqiu Sun, from The Chinese University of Hong Kong and Xiaogang Jin, from State Key Lab of CAD&CG, Zhejiang University in China propose a novel haptic-constraint modeling method based on interactive metaballs, during which the haptic-constraint tools are attracted to the target location and then control the touch-enabled deformation within the constrained areas. The interactive force feedbacks facilitate designers to accurately deform the target regions and fine carve the details as their intention on the objects. Experimental results show that the dynamic sense of touch during the haptic manipulation is intuitively simulated to users, via the interacting interface the authors have developed. Chunyong Ma, Ge Chen, Yong Han, Yongyang Qi, and Yong Chen from Ocean University of China introduce a virtual city oriented VR-GIS platform which synthesizes several latest information technologies including virtual reality, 3D geographical information system, remote sensing, and multi-dimensional visualization. The platform is a seamless integration of VR functions and GIS analysis methods, which can be used to organize and present massive spatial data. It also supplies 3D spatial analysis functions, 3D visualization for spatial process and natural simulation, and serves as an engine platform for digital city The third paper, by Jieje Zhu, from University of Central Florida and Zhigeng Pan, Sun Chao, and Wenzhi Chen from Zhejiang University in China present a method to separate occluded objects in multiple layers by utilizing depth, color, and neighborhood information. Scene depth is obtained by stereo cameras and two Gaussian local kernels are used to represent color, spatial smoothness. These three cues are intelligently fused in a probability framework, where the occlusion information can be safely estimated. They apply their method to handle occlusions in Video-based Augmented Reality where virtual objects are simply overlapped on real scenes. In the fourth paper, Hyewan Seo, Joon-Won Bang, Soon-Hyun Jeon from Chungnam National University, and Ji-Man Park, from Samsung Data Systems in Korea present their work on a 3D billiards game featuring a haptic interface. Most of the existing games available today concentrate on the development of sophisticated physics engines to obtain realistic motion of billiards balls or of sound engines for realistic sound effect. Their focus in this work is on the improved realism on the hitting action of the game with the aid of haptic device. They compute accurate feedback force on the haptic handle, considering the exact point of contact and physically faithful collision response. They present the physically based modeling of the game environment, including the collision interaction among billiards balls, and between the table and billiards balls. Soo Jeong Kim, Jyung Jun Gil, HyungSeok Kim, Sang Beom Lim, and Jee-in Kim from Konkuk University in Korea propose a method to adapt the interfaces and interaction processes of heterogeneous devices. The interaction capability of the devices is modeled by categorizing elementary actions and measuring its effect in semantic behaviors. With this model, an interaction process can be modified to a given device by changing sequence of elementary actions for each behavior. In the pilot test, the authors showed the possibility of interaction adaptation for different situations. With the proposed adaptation mechanism, interface, and interaction can be modeled for the device independently and can be transferred over different interaction environments.

Abstract In this paper we address the problem of creating accurate joint models from real motions while allowing scalability. We propose an automatic method to model, scale, and simulate non‐idealized joints from the external motion of markers. We demonstrate the method on the human knee joint modeling for musculoskeletal analysis and for character animation. The resulting joints, called correlative joints, are character and motion independent and rely on linear combinations of degrees of freedom calculated from multiple regression laws. We show that by using such models, inverse kinematics (IK) solvers find better solutions when tracking motions and solving constraints. Importing correlative joints into new models involves only minimal requirements on landmarks locations and no costly additional computations. Copyright © 2010 John Wiley & Sons, Ltd.

This special issue contains the journal extension of the Best Paper, Best Application and other five selected papers of ACM VRCAI 2008. The first paper by Hanhoon Park, NHK Science & Technical Research Laboratories, Japan, Jihyun Oh, Realtimevisual Inc., Byung-Kuk Seo and Jong-Il Park, Hanyang University, Korea, proposes an automatic method for flexibly adjusting the confidence of visual cues in model-based camera tracking. The adjustment is based on the conditions of the target object/scene and the reliability of the initial or previous camera pose. The method can achieve real-time performance and successfully applied to a mobile augmented reality (AR) guidance system for a museum. This paper is the Best Paper of VRCAI 2008. The second paper, by Guangzheng Fei, Communication University of China, Won-Sook Lee, University of Ottawa, Canada, Zijun Xin and Huikai Dong, Communication University of China, and Chris Joslin, Carleton University, Canada, describes an animation creation system called PASCAL that supports sketch based modeling and physics augmented locomotion simultaneously. The system uses sketches and reconfigurable space canvases as basic modeling primitives and uses physics to improve the expressiveness and efficiency of several animation techniques to obtain controllable and plausible locomotion animation. The usability evaluation of the system was conducted both with professional and novice animators. This paper wins the Best Application of VRCAI 2008. In the third paper, Yimin Wang and Jianmin Zheng, from Nanyang Technological University, Singapore, propose an edge-based parameterization method, in which the edges rather than the vertices of the mesh are treated as the target for parameterization. It first parameterizes the edges on the two boundaries of the tubular mesh, then parameterizes the internal edges based on the mean value coordinates, and finally computes the parameters of the mesh vertices. The method does not need cutting of the mesh. It improves conventional cutting-based algorithms, which cut the mesh to make it a disk topologically, and overcomes the problems of cutting paths that are the zigzag paths leading to suboptimal parameterizations and the difficulty in finding good cutting paths. Some applications such as surface fitting and texture mapping are also provided. Jie Zhang, Soh-Khim Ong, and Andrew Yeh-Ching Nee from National University of Singapore, present, in the next paper, an implementation of machining simulation in a real machining environment applying AR technology. This in situ machining simulation system allows a machinist to analyze the simulation process, adjust the machining parameters, and observe the results in real-time in a real machining environment. Such a system is useful for machinists and trainees during the trial and learning stages, allowing them to experiment with different machining parameters on a real machine without having to worry about possibilities of machine and tool breakages. Experiments were conducted on a real 3-axis CNC machine to validate and evaluate the performance of the system and the feedback from a survey carried out with the experiments is very positive. Corey Manders, Farzam Farbiz, Ka Yin Tang, Miaolong Yuan, Gim Guan Chua, and Susanto Rahardja of A*STAR Institute for Infocomm Research, Singapore, present, in the next paper, a system for interacting with 3D objects in a 3D virtual environment. Using the notion that a typical head-mounted display does not cover the user's entire face, they use a fiducial marker placed on the HMD to locate the user's exposed facial skin. Using this information, a skin model is built and combined with the depth information obtained from a stereo camera. The information when used in tandem allows the position of the user's hands to be detected and tracked in real time. Once both hands are located, the system allows the user to manipulate the object with five degrees of freedom (translation in x, y, and z axis with roll and yaw rotations) in virtual three-dimensional space using a series of intuitive hand gestures. In the sixth paper, by Jiejie Zhu and Zhigeng Pan of Beihang University and Zhejiang University, Chao Sun of Beihang University, and Wenzhi Chen of Zhejiang University, China, the authors propose an approach to separate occluded objects in multiple layers by utilizing depth, color, and neighborhood information. Scene depth is obtained by stereo cameras and two Gaussian local kernels are used to represent color and spatial smoothness. These three cues are intelligently fused in a probability framework, where the occlusion information can be safely estimated. Experiment results showed that the approach can correctly register virtual and real objects in different depth layers, and provide a spatial-awareness interaction environment. The seventh paper is also the last paper by Chunyong Ma, Ge Chen, Yong Han, Yongyang Qi, and Yong Chen of Ocean University of China. The paper introduces a virtual city oriented VR-GIS platform which synthesizes several latest information technologies including virtual reality, 3D geographical information system, remote sensing and multi-dimensional visualization. The platform is a seamless integration of VR functions and GIS analysis methods, which can be used to organize and present massive spatial data. It also supplies 3D spatial analysis functions, 3D visualization for spatial process and natural simulation, and serves as an engine platform for digital city. The two last papers will appear in the 5th regular special issue.

Populating virtual environments (VEs) with large crowds is a subject that has been tackled for several years. Solutions have been proposed to offer realistic trajectories as well as interactivity, but limitations remain on the environment dimensions with respect to population density. In this paper, we extend the concept of motion patches [Lee et al. 2006] to densely populate large environments. We build a population from a set of blocks containing a pre-computed local crowd simulation. Each block is called a crowd patch. We address the problem of computing patches, assembling them to create VEs, and controlling their content to answer designers' needs. Our major contribution is to provide a drastic lowering of computation needs for simulating a virtual crowd at run-time. We can thus handle dense populations in large-scale environments with performances never reached so far. Our results illustrate the real-time population of a potentially infinite city with realistic and varied crowds interacting with each other and their environment. We discuss the advantages and drawbacks of the proposed solution, and its possible improvements in the future.

Due to its intrinsic complexity, full-body postural input has been mostly limited to off-line motion capture and to on-line puppetry of a virtual character with little interaction with its environment (e.g. floor). The motion capture technology is now mature enough to envision the on-line full-body postural control of virtual mannequins involved in precise reaching tasks. We have investigated such tasks for mannequins of differing body heights in comparison to that of the system user. Such broad-range avatar control is relevant for virtual prototyping in various industrial sectors as a single person is responsible for evaluating a virtual prototype for a full range of potential end-users. In the present paper we report on two scaling strategies that can be enforced in such a context of height-differing avatar control. Both scaling strategies have been evaluated in a wide-range reach study both in front of a stationary immersive display and with an HMD. A comparison is also made with a baseline scenario, which exploits a simple rigid shape (i.e. a proxy), to assess the specific influence of controlling a complex articulated avatar.

Abstract Crowd animation is a topic of high interest which offers many challenges. One of the most important is the trade‐off between rich, realistic behaviors, and computational costs. To this end, much effort has been put into creating variety in character representation and animation. Nevertheless, one aspect still lacking realism in virtual crowd characters resides in their attention behaviors. In this paper, we propose a framework to add gaze attention behaviors to crowd animations. First, we automatically extract interest points from character or object trajectories in pre‐ existing animations. For a given character, we assign a set of elementary scores based on parameters such as distance or speed to all other characters or objects in the scene. We then combine these subscores in an overall scoring function. The scores obtained from this function form a set of gaze constraints that determine where and when each character should look. We finally enforce these constraints with an optimized dedicated gaze Inverse Kinematics (IK) solver. It first computes the displacement maps for the constraints to be satisfied. It then smoothly propagates these displacements over an automatically defined number of frames. We demonstrate the efficiency of our method and our visually convincing results through various examples. Copyright © 2009 John Wiley & Sons, Ltd.

Dematerialized music and MP3 players offer to the user the possibility of carrying his musical content everywhere. However, at home, the music collection is generally not centralized, split between different rooms and audio supports (CDs, MP3s, etc). In this paper, we propose a multi-room sound system based on several sound satellites distributed among the rooms of the house, and on a remote control which is able to localize itself with the help of available Wi-Fi networks. The user only has to choose his favorite music on the remote control, and then the music will automatically start on the nearest satellites. Our goal is to offer an ambient intelligence audio system, inspired by the latest multi-room sound systems, which takes advantage of an indoor localization system based on Wi-Fi in order to propose a new experience to the user.

In this paper, we present the technical details and the challenges we faced during the development and evaluation phases of our wearable indoor guiding system which consists of a virtual personal assistant guiding the user to his/her desired destination. The main issues that will be discussed can be classified in three categories: context detection, real-time 3D rendering and user interaction.

By nature, human beings perceive their environment mostly using sight and audition. Vibrotactile feedback has proven satisfying results in the domains of simple multimodal interaction, for immersion and navigation purposes. The scope of this research is to evaluate the additional value of tactile feedback on the user upper body limbs to pass 3D directional information. This paper presents the development of a vibrotactile jacket and its software interface. A validation concept test bench has been setup to measure the effect of our vibrotactile device onto the response time to localize a target in a virtual environment over visual and auditory cue. Early results are encouraging by showing clear benefits of our vibrotactile system while the complexity of the multimodal environment is increasing.

This tutorial will present the latest techniques to model fast individualized animatable virtual humans for Real-Time applications. As a human is composed of a head and a body, we will analyze how these two parts can be modeled and globally animated as in real-life. More precisely, we will show how we can model and deform human bodies and heads. Facial animation will be also addressed from motion facial capture and voice to the simulation of interactive realistic talking virtual humans, including personality models and complete body gestures. We will describe how we can model crowds in realtime using dynamic meshes, static meshes and impostors. Techniques to introduce variety in crowds including individual animation with accessories will be explained.

This issue contains five regular papers. The first paper, by Marcelo Kallmann from University of California in Merced, USA, presents a novel whole-body analytical Inverse Kinematics (IK) method integrating collision avoidance and customizable body control for animating reaching tasks in real-time. Body control is achieved with the interpolation of pre-designed key body postures, organized as a function of the direction to the goal to be reached. Arm postures are computed by the analytical IK solution for human-like arms and legs, extended with a new simple search method for achieving postures avoiding joint limits and collisions. In addition, a new IK resolution is presented that directly solves for joints parameterized in the swing-and-twist decomposition. The second paper, by Man Hee Lee and In Kyu Park from Inha University in Korea, explains an image-based method for modeling 3D objects with curved surfaces based on the NURBS representation. The user fits the feature curves on a few calibrated images with 2D NURBS curves using the interactive user interface. Then, 3D NURBS curves are constructed by stereo reconstruction of the corresponding feature curves. Using these as building blocks, NURBS surfaces are reconstructed by the known surface building methods including bilinear surfaces, ruled surfaces, generalized cylinders, and surfaces of revolution. In the third paper, Frank Patrick Vidal and Nigel W. John from University of Wales and Derek A. Gould and Andrew E. Healey from the Royal Liverpool University in UK present an integrated system for training ultrasound guided needle puncture. Their aim is to provide a validated training tool for Interventional Radiology (IR) that uses actual patient data. A hybrid surface/volume haptic rendering of an ultrasound transducer is proposed to constrain the device to remain outside the bony structures when scanning the patient's skin. The authors also propose a volume haptic model that implements an effective model of needle puncture. Force measurements have been made on real tissue and the resulting data are incorporated into the model. Seunghyun Han, Mingyu Lim, Dongman Lee, and Soon J. Hyun, from the Information and Communications University in Korea, introduce, in the next paper, a scalable interest management scheme for Distributed Virtual Environments. Their new scalable filtering scheme reduces not only the number of messages during interaction in a region and among neighboring regions, but also the number of multicast addresses without significant computational overhead. For interaction among neighboring regions, the authors propose a sub-region concept to select only a subset of users from the neighboring regions based on proximity, the distribution of the users, locations, and the viewing direction of a user. The last paper, by Anderson Maciel and Suvranu De from the Rensselaer Polytechnic Institute in USA, presents an efficient dynamic point algorithm for line-based collision detection in real-time Virtual Environments. The algorithm for computing the interaction with a line-shaped haptic cursor has a near constant complexity. It relies on space-time coherence and topological information to maintain proximity information between a line segment and triangle meshes. The line is represented by a dynamic point, which is chosen to be the closest point on the line to any potentially colliding triangle. The algorithm may be used for collision detection and response with rigid and deformable objects with no performance penalty.

This issue contains four regular papers and the two best papers of ICEC 2007. The first paper, by Silvia Rueda, Pedro Morillo, and Juan Orduña from the University of Valencia, Spain, proposes a comparative study of the performance provided by awareness methods that are supposed to fully solve the awareness problem in peer-to-peer distributed virtual environments. The paper evaluates the performance of the considered methods on actually distributed systems. The evaluation results show that only a single method actually provides full awareness to avatars. The second paper, by Fan Zhang, Hanqiu Sun, and Chong Zhao, from The Chinese University of Hong Kong, and Lifeng Wang from Autodesk Software, presents an enhanced variant of light space perspective shadow maps to optimize perspective aliasing distribution in possible general cases where the light and view directions are not orthogonal. Authors' experiments have shown the enhanced shadow quality using their algorithm in dynamic scenes. This paper is one of the best papers of ICEC 2007. In the third paper, Liying Wang, Wei Hua, and Hujun Bao, from Zhejiang University, China, formulate the urban planning as a constrained layout optimization problem; they propose an algorithm to solve the problem and procedurally generate models of urban zone. It produces extensive virtual urban environment for computer games and simulations at a low cost. Experimental results prove that their method can efficiently produce the virtual urban scene similar to that designed by urban planners. This paper is one of the best papers of ICEC 2007. Marco Gillies, Xueni Pan, Mel Slater, and John Shawe-Taylor from University College London, UK, introduce, in the next paper, an important aspect of non-verbal expression: people respond to each other's behavior and are highly attuned to picking up this type of response. The paper takes a data driven approach to generating interactive social behavior. Listening behavior is motion captured, together with the audio being listened to. These data are used to learn an animation model of the responses of one person to the other. This allows us to create characters that respond in real-time during a conversation with a real human. Umberto Castellani, from University of Verona, Italy, and Vincent Gay-Bellile and Adrien Bartoli from Universitè Blaise Pascal, The Puy-de-Dôme, France, present, in the next paper, a deformation capture system for surfaces from temporal range data obtained by 3D sensors. The proposed method is based on planar mesh that is deformed so as to fit each range image. The authors show how this is achieved by minimizing a compound cost function combining several data and regularization terms, needed to make the overall system robust so that it can deal with low quality datasets. In the last paper, by James Anderson, Nancie Davidson, Hazel Morton, and Mervyn Jack, from University of Edinburgh, UK, the authors introduce The Spoken Electronic Language Learning (SPELL) system. It is a self-access computer-assisted language learning package that integrates speaker-independent continuous speech recognition technology with virtual worlds and embodied virtual agents. The goal is to create an environment in which learners can converse in the target language within meaningful contextualized scenario. The paper focuses on the technological aspects of the system and its evaluation for usability and robustness, rather than its pedagogical methodology.

Abstract In this issue, you will find a special section on Wireless and Mobile Technologies in Mixed Realities, with four papers introduced by the two guest editors Gurminder Singh and Georges Papagiannakis. The last paper of the issue is a regular paper by I. Mansa et al. entitled “Analysis of coherence strategies for stereo occlusion culling.” This paper explores the benefits that can be achieved for stereoscopic visualization when using occlusion‐culling strategies. It shows the limitations placed by compact and not densely occluded scenarios and the gains that can be achieved when rendering stereo images using occlusion culling. The experiments carried out test combinations of occlusion stereo coherence and occlusion frame coherence. The algorithm presented can be easily implemented and provides a significant boost in performances.

Real-time crowd motion planning requires fast, realistic methods for path planning as well as obstacle avoidance. The difficulty to find a satisfying trade-off between efficiency and believability is particularly challenging, and prior techniques tend to focus on a single approach. In this paper, we present a hybrid architecture to handle the path planning of thousands of pedestrians in real time, while ensuring dynamic collision avoidance. The scalability of our approach allows to interactively create and distribute regions of varied interest, where motion planning is ruled by different algorithms. Practically, regions of high interest are governed by a long-term potential field-based approach, while other zones exploit a graph of the environment and short-term avoidance techniques. Our method also ensures pedestrian motion continuity when switching between motion planning algorithms. Tests and comparisons show that our architecture is able to realistically plan motion for many groups of characters, for a total of several thousands of people in real time, and in varied environments.

This paper presents a new library called MHaptic for bimanual haptic interaction within generic virtual environments. It has been specifically designed to work with a Haptic WorkstationTM. MHaptic provides tools for accelerated development of virtual environment applications with haptic feedback like device calibration, user comfort improvements and access to low level parameters. Due to its integration with the Ageia PhysX library, it facilitates the dynamic animation of virtual objects. A realistic hand model based on mass-spring systems allows natural and intuitive manipulation. MHaptic is complemented by an authoring tool that associates information required for haptic feedback to existing virtual environments. The combination of the library and the authoring tool creates a framework for easy development of complex VR haptic applications.

This paper presents a solution to interactive navigation planning and real-time simulation of a very large number of entities moving in a virtual environment. From the environment geometry analysis, we deduce a structure called navigation graph, which is the base to our method. After the description of this structure, we introduce a set of algorithms dedicated to answer navigation queries with a set of various solution paths and to execute the planned navigation in an efficient manner. We equally demonstrate method performance and robustness over several examples.

Interactive control of a virtual character through full body movement has a wide range of applications. However, there is a need for systems that accurately reproduce the motion of a performer while accounting for surrounding obstacles. We propose an approach based on a Prioritized Inverse Kinematics constraint solver. Several markers are placed on the user's body. A set of kinematic constraints make the virtual character track these markers. At the same time, we monitor the instantaneous displacements of a set of geometric primitives, called observers, attached to different parts of the virtual character. When an observer enters the influence area of an obstacle, its motion is damped by means of automatically created preventive constraints. The IK solver satisfies both maker and preventive constraints simultaneously, yielding postures of the virtual character that remain close to those of the user, while avoiding collisions with the virtual environment. Our performance measurements show the maturity of the IK technology for real-time full-body interactions.

With the advent of ubiquitous and pervasive computing environments, one of promising applications is a guidance system. In this paper, we propose a mobile mixed reality guide system for indoor environments, [email protected] A mobile computing device (Sony's Ultra Mobile PC) is hidden inside a jacket and a user selects a destination inside a building through voice commands. A 3D virtual assistant then appears in the see-through HMD and guides him/her to destination. Thus, the user simply follows the virtual guide. [email protected] also suggests the most suitable virtual character (e.g. human guide, dog, cat, etc.) based on user preferences and profiles. Depending on user profiles, different security levels and authorizations for content are previewed. Concerning indoor location tracking, WiFi, RFID, and sensor-based methods are integrated in this system to have maximum flexibility. Moreover smart and transparent wireless connectivity provides the user terminal with fast and seamless transition among Access Points (APs). Different AR navigation approaches have been studied: [Olwal 2006], [Elmqvist et al.] and [Newman et al.] work indoors while [Bell et al. 2002] and [Reitmayr and Drummond 2006] are employed outdoors. Accurate tracking and registration is still an open issue and recently it has mostly been tackled by no single method, but mostly through aggregation of tracking and localization methods, mostly based on handheld AR. A truly wearable, HMD based mobile AR navigation aid for both indoors and outdoors with rich 3D content remains an open issue and a very active field of multi-discipline research.

Abstract This paper explores the issue of interactive low‐dimensional human motion synthesis. We compare the performances of two motion models, i.e. Principal Components Analysis (PCA) or Probabilistic PCA (PPCA), for solving a constrained optimization problem within a low‐dimensional latent space. We use PCA or PPCA as a first step of preprocessing to reduce the dimensionality of the database to make it tractable, and to encapsulate only the essential aspects of a specific motion pattern. Interactive user control is provided by formulating a low‐dimensional optimization framework that uses a Prioritized Inverse Kinematics (PIK) strategy. The key insight of PIK is that the user can adjust a motion by adding constraints with different priorities. We demonstrate the robustness of our approach by synthesizing various styles of golf swing. This movement is challenging in the sense that it is highly coordinated and requires a great precision while moving with high speeds. Hence, any artifact is clearly noticeable in the solution movement. We simultaneously show results comparing local and global motion models regarding synthesis realism and performance. Finally, the quality of the synthesized animations is assessed by comparing our results against a per‐frame PIK technique. Copyright © 2007 John Wiley & Sons, Ltd.

Handling the evolving permanent contact of deformable objects leads to a collision detection problem of high computing cost. Situations in which this type of contact happens are becoming more and more present with the increasing complexity of virtual human models, especially for the emerging medical applications. In this context, we propose a novel collision detection approach to deal with situations in which soft structures are in constant but dynamic contact, which is typical of 3D biological elements. Our method proceeds in two stages: First, in a preprocessing stage, a mesh is chosen under certain conditions as a reference mesh and is spherically sampled. In the collision detection stage, the resulting table is exploited for each vertex of the other mesh to obtain, in constant time, its signed distance to the fixed mesh. The two working hypotheses for this approach to succeed are typical of the deforming anatomical systems we target: First, the two meshes retain a layered configuration with respect to a central point and, second, the fixed mesh tangential deformation is bounded by the spherical sampling resolution. Within this context, the proposed approach can handle large relative displacements, reorientations, and deformations of the mobile mesh. We illustrate our method in comparison with other techniques on a biomechanical model of the human hip joint.

Despite its history of several decades and impressive achievements, developing a VR application is still a complex task. Setting-up a Virtual Environment requires choosing a suitable combination of elements from a large amount of technologies, software frameworks, animation/modeling formats and many other components. In this paper we present an overview of the efforts focused on defining a commonly accepted set of specifications -standards- for the multiple "ingredients" of a VR application. Our analysis of current and previous initiatives provides elements to answer the question about whether or not we can talk about "standard VR".

Instead of the reality in which you can see your own limbs, in virtual reality simulations it is sometimes disturbing not to be able to see your own body. It seems to create an issue in the proprio-perception of the user who does not completely feel integrated in the environment. This perspective should be beneficial for the users. We propose to give the possibility to the people to use the first and the third-person perspective like in video games (e.g. GTA). As the gamers prefer to use the third-person perspective for moving actions and the first-person view for the thin operations, we will verify this comportment is extendable to simulations in augmented and virtual reality.

Abstract This paper presents an original model with methodologies that integrate in a novel way different types of an autonomous virtual agent's perception in a virtual environment. Our first new approach permits the coherent management of the shared virtual environment for the simulations of an autonomous virtual agent (AVA). Our second approach allows the prediction or the estimation of both the orientation and the attention of an AVA in a virtual environment. By means of a test application with a ‘virtual goalkeeper’, we demonstrate the speed and the robustness of our technique. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract Expressive facial animation synthesis of human like characters has had many approaches with good results. MPEG‐4 standard has functioned as the basis of many of those approaches. In this paper we would like to lay out the knowledge of some of those approaches inside an ontology in order to support the modeling of emotional facial animation in virtual humans (VH). Inside this ontology we will present MPEG‐4 facial animation concepts and its relationship with emotion through expression profiles that utilize psychological models of emotions. The ontology allows storing, indexing and retrieving prerecorded synthetic facial animations that can express a given emotion. Also this ontology can be used a refined knowledge base in regards to the emotional facial animation creation. This ontology is made using Web Ontology Language and the results are presented as answered queries. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract This paper introduces a framework for real‐time simulation and rendering of crowds navigating in a virtual environment. The solution first consists in a specific environment preprocessing technique giving rise to navigation graphs, which are then used by the navigation and simulation tasks. Second, navigation planning interactively provides various solutions to the user queries, allowing to spread a crowd by individualizing trajectories. A scalable simulation model enables the management of large crowds, while saving computation time for rendering tasks. Pedestrian graphical models are divided into three rendering fidelities ranging from billboards to dynamic meshes, allowing close‐up views of detailed digital actors with a large variety of locomotion animations. Examples illustrate our method in several environments with crowds of up to 35 000 pedestrians with real‐time performance. Copyright © 2006 John Wiley & Sons, Ltd.

In this paper, we present our spreadsheet framework, which uses a spreadsheet-like interface for exploring biomedical datasets. The principles and advantages of this class of visualization systems are illustrated, and a case study for the analysis of hip joint congruity is presented. Throughout this use case, we see how end users can compare different datasets, apply parallel operations on data, create analysis templates, and how this helps them in the exploration process.

Motion blending is widely accepted as a standard technique in computer animation, allowing the generation of new motions by interpolation and/or transition between motion capture sequences. To ensure smooth and seamless results, an important property has to be taken into account: similar constraints sequences have to be time aligned. But traditional blending approaches let the user choose manually the transition time and duration. In addition, according to the animation context, blending operations should not be performed immediately. They can only occur during a precise period of time, while preserving specific physical properties. We present in this paper an improved blending technique allowing automatic controlled transition between motion patterns whose parameters are not known in advance. This approach ensures coherent movements over the parameter space of the original input motions. To illustrate our approach, we focus on walking and running motions blended with jumps, where animators may vary the jump length and style. The proposed method specifies automatically the support phases of the input motions, and controls on the fly a correct transition time. Moreover the current locomotion type and speed are smoothly adapted given a specific jump type and length.

Nowadays virtual humans such as non-player characters in computer games need to have a real autonomy in order to live their own life in persistent virtual worlds. When designing autonomous virtual humans, the action selection problem needs to be considered, as it is responsible for decision making at each moment in time. Action selection architectures for autonomous virtual humans should be individual, motivational, reactive and proactive to obtain a high degree of autonomy. This paper describes in detail our motivational model of action selection for autonomous virtual humans in which overlapping hierarchical classifier systems, working in parallel to generate coherent behavioral plans, are associated with the functionalities of a free flow hierarchy to give reactivity to the hierarchical system. Finally, results of our model in a complex simulated environment, with conflicting motivations, demonstrate that the model is sufficiently robust and flexible for designing motivational autonomous virtual humans in real-time.

We present a system for real-time configuration of multimodal interfaces to Virtual Environments (VE). The flexibility of our tool is supported by a semantics-based representation of VEs. Semantic descriptors are used to define interaction devices and virtual entities under control. We use portable (XML) descriptors to define the I/O channels of a variety of interaction devices. Semantic description of virtual objects turns them into reactive entities with whom the user can communicate in multiple ways. This article gives details on the semantics-based representation and presents some examples of multimodal interfaces created with our system, including gestures-based and PDA-based interfaces, amongst others.

This paper presents an innovative 3D reconstruction of ancient fresco paintings through the real-time revival of their fauna and flora, featuring groups of virtual animated characters with artificial-life dramaturgical behaviours in an immersive, fully mobile augmented reality (AR) environment. The main goal is to push the limits of current AR and virtual storytelling technologies and to explore the processes of mixed narrative design of fictional spaces (e.g. fresco paintings) where visitors can experience a high degree of realistic immersion. Based on a captured/real-time video sequence of the real scene in a video-see-through HMD set-up, these scenes are enhanced by the seamless accurate real-time registration and 3D rendering of realistic complete simulations of virtual flora and fauna (virtual humans and plants) in a real-time storytelling scenario-based environment. Thus the visitor of the ancient site is presented with an immersive and innovative multi-sensory interactive trip to the past. Copyright © 2005 John Wiley & Sons, Ltd.

This paper aims to propose a novel approach to generate new generic human walking patterns using motion-captured data, leading to a real-time engine intended for virtual humans animation. The method applies the PCA (principal component analysis) technique on motion data acquired by an optical system to yield a reduced dimension space where not only interpolation, but also extrapolation are possible, controlled by quantitative speed parameter values. Moreover, with proper normalization and time warping methods, the generic presented engine can produce walking motions with continuously varying human height and speed with real-time reactivity

After implementing a motivational model of action selection applied to autonomous virtual humans inspired by models of animals' decision-making, the problem consists of testing it in good conditions for validation. Indeed this model has to respect the six criteria that we define according to Tyrell's requirements for designing a mechanism of action selection. So we use the real-time framework VHD++ for advanced virtual human simulation and we define a simulated environment with many conflicting motivations. Finally a video shows the first results where the virtual human's decision-making follows the six criteria and so validates our model in the simulated environment

This paper presents a novel method of collaborative problem solving for intelligent agents in virtual environments. We describe a planner for STRIPS-like domains enhanced by techniques of "delegated computing". Instead of having one central planner with complete information about the world, the concept of delegation is used. In this way, we achieve agent collaboration in a dynamic system, where each of the agents has its own partial plan, but the plans are implicitly coordinated towards a common goal. We demonstrate these techniques in a virtual reality simulation with virtual humans solving a logistical problem.

This article shows that the creation of cyberworlds (interactive virtual environments) can be an excellent educational tool covering a wide range of computer science and engineering disciplines. We present the experiences gathered during more than one semester of work with computer science students in the framework of semester projects developed at the virtual reality lab of EPFL. Our objective is to share the lessons learnt by both the students and researchers (project advisors). We describe the projects proposed, the methods applied to help the students reach the objectives, the problems faced during the development work and how we managed to solve them.

The present paper describes the integration of a multi-finger haptic device with deformable objects in an interactive environment. Repulsive forces are synthesized and rendered independently for each finger of a user wearing a Cybergrasp force-feedback glove. Deformation and contact models are based on mass-spring systems, and the issue of the user independence is dealt with through a geometric calibration phase. Motivated by the knowledge that human hand plays a very important role in the somatosensory system, we focused on the potential of the Cybergrasp device to improve perception in Virtual Reality worlds. We especially explored whether it is possible to distinguish objects with different elasticities. Results of performance and perception tests are encouraging despite current technical and computational limitations.

This paper addresses evaluation and visualization of stress and strain on soft biological tissues in contact given three-dimensional models of reconstructed organs from magnetic resonance images (MRI), we use an anatomy-based kinematical model combined with a soft tissues model to represent their shape and behavior. Then, we compute resulting distribution of stress and strain on deforming surface when motion is simulated. The computed stress and strain are then effectively visualized using an interactive animation framework. Experimental results are illustrated in the case of the hip joint cartilage.

This paper presents a telerehabilitation system for kinesthetic therapy (treatment of patients with arm motion coordination disorders). Patients can receive therapy while being immersed in a virtual environment (VE) with haptic feedback. Our system is based on a Haptic Workstation that provides force-feedback on the upper limbs. One of our main contributions is the use of a handheld device as the main interface for the therapist. The handheld allows for monitoring, adapting and designing exercises in real-time (dynamic VE). Visual contact with the patient is kept by means of a webcam.

Abstract Representing motions as linear sums of principal components has become a widely accepted animation technique. While powerful, the simplest version of this approach is not particularly well suited to modeling the specific style of an individual whose motion had not yet been recorded when building the database: it would take an expert to adjust the PCA weights to obtain a motion style that is indistinguishable from his. Consequently, when realism is required, the current practice is to perform a full motion capture session each time a new person must be considered. In this paper, we extend the PCA approach so that this requirement can be drastically reduced: for whole classes of cyclic and noncyclic motions such as walking, running or jumping, it is enough to observe the newcomer moving only once at a particular speed or jumping a particular distance using either an optical motion capture system or a simple pair of synchronized video cameras. This one observation is used to compute a set of principal component weights that best approximates the motion and to extrapolate in real‐time realistic animations of the same person walking or running at different speeds, and jumping a different distance.

Abstract Our approach is based on the multi‐sensory integration of the standard theory of neuroscience, where signals of a single object coming from distinct sensory systems are combined. The acquisition steps of signals, filtering, selection and simplification intervening before proprioception, active and predictive perception are integrated into virtual sensors and a virtual environment. We will focus on two aspects: 1) the assignment problem: determining which sensory stimuli belong to the same virtual object and (2) the sensory recoding problem: recoding signals in a common format before combining them. We have developed three novel methodologies to map the information coming from the virtual sensors of vision, audition and touch as well as that of the virtual environment in the form of a ‘cognitive map’. Copyright © 2004 John Wiley & Sons, Ltd.

This last issue of 2004 contains three papers.The first deals with the rendering of natural waters taking fluorescence into account.This is a step forward to more realism.

This article addresses 2-dimensional layout of high-dimensional biomedical datasets, which is useful for browsing them efficiently We employ the isomap technique, which is based on classical MDS (multi-dimensional scaling) but seeks to preserve the intrinsic geometry of the data, as captured in the geodesic manifold distances between all pairs of data points while classical approaches can see just the Euclidean structure. According to first two of isomap's coordinates, the high-dimensional data points are arranged in a plane. Experimental results with images of marine creatures' shapes and 3D bone renderings are presented.

This article addresses visualization of deformation or shape differences between bones while conventional visualization techniques are often about a single bone such as its 3D reconstruction. Given a pair of bones with a set of corresponding anatomical landmarks, we compute displacement vectors describing the deformation from one bone to the other at the landmark points on one of the bones. Out of these prescribed ones, a displacement vector at each vertex on the bone surface is derived using a multi-level approximation technique of scattered data. Based on the value of inner product between a displacement vector and a surface normal at each vertex, color is mapped. Considering error-prone estimation of the landmark location in real applications, approximations at different levels are realized instead of exact interpolation as usually done in elastic image registration. Experimental results on a pair of femoral bones are presented.

In most vehicle simulators, complete physical mockups equipped with steering wheel, gearshift and pedals are required. These devices are essential in trying to simulate real conditions, but as a drawback the system becomes expensive, huge (non mobile), and limited to reflect changes on the vehicle type, dimensions, or interior design. We have implemented different configurations for an immersive vehicle simulator, ranging from the use of a real mockup equipped with force-feedback steering wheel, gearshift and pedals, to fully virtual control metaphors, which are based only on trackers and datagloves. We propose such fully virtual control metaphors as an alternative to minimize the use of physical devices in simulators.

We present the architecture of the VHD++ real-time development framework that after several years of intensive research, design, and development effort has been released and enters its validation phase. We discuss the key aspects involved in architectural structure, design and practical implementation of an efficient, flexible and extendible real-time software framework based on the modern 3D game-engine design principles. This framework supports researchers and application developers with rapid, component based development of VR/AR systems featuring advanced virtual character simulation technologies. The discussion covers motivation, main concepts, survey of related work, the main functional and design requirements, design principles and key architectural elements. It concludes with the initial validation results including overview of existing VHD++ based VR/AR virtual character simulation applications.

This paper presents an evaluation of the benefits and user acceptance of a multimodal interface in which the user interacts with a game-like interactive virtual reality application "The Enigma of the Sphinx". The interface consists of a large projection screen as the main display, a "magic wand", a stereo sound system and the user's voice for "casting spells". We present our conclusions concerning "friendliness" and sense of presence, based on observations of more than 150 users in a public event.

We define cyberpeople as people represented on thenet using embodiment. These people can be either Avatarsthat are a representation of a real human or completelysynthesized virtual humans or Autonomous VirtualAgents (AVAs). In this paper, we discuss the two kinds ofcyberpeople and show how it will become difficult in thenear future to distinguish Avatars from AVAs. We willdemonstrate with examples how embodied agents becomemore and more intelligent and autonomous.

We present a method for improving robustness in feature-based tracking of human motion. Motion flows of features estimated by a standard tracker are modified to be coherent with neighboring ones. This coherence constraint is computed based on a smooth approximation to initial motion flows computed by the tracker. With these tracking results, we demonstrate motion segmentation of different body parts in an image sequence.

We present a fully automated approach to camera registration for augmented reality systems. It relies on purely passive vision techniques to solve the initialization and real-time tracking problems, given a rough CAD model of parts of the real scene. It does not require a controlled environment, for example placing markers. It handles arbitrarily complex models, occlusions, large camera displacements and drastic aspect changes. This is made possible by two major contributions: the first one is a fast recognition method that detects the known part of the scene, registers the camera with respect to it, and initializes a real-time tracker, which is the second contribution. Our tracker eliminates drift and jitter by merging the information from preceding frames in a traditional recursive tracking fashion with that of a very limited number of key-frames created off-line. In the rare instances where it fails, for example because of large occlusion, it detects the failure and reinvokes the initialization procedure. We present experimental results on several different kinds of objects and scenes.

This real-time augmented reality demonstration relies on our tracking algorithm described in V. Lepetit et al (2003). This algorithm considers natural feature points, and then does not require engineering of the environment. It merges the information from preceding frames in traditional recursive tracking fashion with that provided by a very limited number of reference frames. This combination results in a system that does not suffer from jitter and drift, and can deal with drastic changes. The tracker recovers the full 3D pose of the tracked object, allowing insertion of 3D virtual objects for augmented reality applications.

The tutorial will explain the techniques for integrating virtual humans into virtual and real environments. It will first present the concept of avatars and autonomous virtual actors and the main techniques to create and animate them (body and face). It will present the concepts of behavioral animation, crowd simulation, intercommunication between virtual humans, and interaction between real humans and autonomous virtual humans. The tutorial will also address the advanced topics of real-time cloth animation with application in fashion design. Finally, the tutorial will present the use of the virtual human technology in virtual heritage, social phobia, training, and health emergency.

Abstract We present new techniques that use motion planning algorithms based on probabilistic roadmaps to control 22 degrees of freedom (DOFs) of human‐like characters in interactive applications. Our main purpose is the automatic synthesis of collision‐free reaching motions for both arms, with automatic column control and leg flexion. Generated motions are collision‐free, in equilibrium, and respect articulation range limits. In order to deal with the high (22) dimension of our configuration space, we bias the random distribution of configurations to favor postures most useful for reaching and grasping. In addition, extensions are presented in order to interactively generate object manipulation sequences: a probabilistic inverse kinematics solver for proposing goal postures matching pre‐designed grasps; dynamic update of roadmaps when obstacles change position; online planning of object location transfer; and an automatic stepping control to enlarge the character's reachable space. This is, to our knowledge, the first time probabilistic planning techniques are used to automatically generate collision‐free reaching motions involving the entire body of a human‐like character at interactive frame rates. Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three‐Dimensional Graphics and Realism

The MPEG-4 standard specifies a set of low-level animation parameters for body animation, but does not provide any high-level functionality for the control of avatars or embodied agents. In this paper we discuss the required features for a script format allowing designers to easily specify complex bodily behaviors, and describe a system and its associated syntax - Body Animation Script (BAS) - which fulfills these requirements in a flexible way. The described architecture allows the organization and parametrization of predefined MPEG-4 animations and their integration with real-time algorithmic animations, such as pointing at a specific location or walking. This system has been implemented at EPFL in the framework of the EU SoNG project, in order to allow intelligent software agents to control their 3D graphical representation and end-users to trigger rich nonverbal behaviors from an online interface. It has been integrated into AML - the Avatar Markup Language.

Interactive systems, games, VR and multimedia systems require more and more flexible Virtual Humans with individualities. Behavioral animation seems to be the best way to develop this kind of applications, but there is still a major problem to select the right laws and rules to implement individual but believable behaviors. To create motion laws, there are mainly two approaches: 1) Recording the motion using motion capture systems, then to try to alternate such a motion to create this individuality. This process is tedious and there is no reliable method at this stage. 2) Creating computational models which are controlled by a few parameters. One of the major problem is to find such models and to compose them to create complex motion. Such models can be created for walking, grasping, but also for groups and crowds.

This article describes an approach based on hierarchical radial basis functions for the reconstruction and modification of motion/image data, which are formulated as problems of scattered data interpolation. Assuming little about the data and choosing highly scalable/well adjustable basis functions, the approach can handle both the reconstruction and the manipulation in a unified and widely applicable manner: standard approaches are often applicable, but have limited scope due to their constrained assumptions about the number or location of the data points. Reconstruction of captured motion data and warping of face images are demonstrated.

This article describes a method of constructing parametric models out of captured motion and skeleton data. Casting the problem as scattered data interpolation, our work is based on a multi-step approximation for the interpolation function with motion data compressed by principal component analysis. This leads to smaller storage and faster computation than those of previous approaches based on classical methods of exact interpolation. As a result, motion models can be constructed out of a rich set of example data, but can be used for real-time applications. We demonstrate a motion model controllable by attributes including those invariant for each individual, such as age, gender, height and weight. A parametric skeleton model is also constructed and demonstrated.

Abstract While virtual crowds are becoming common in non‐real‐time applications, the real‐time domain is still relativelyunexplored. In this paper we discuss the challenges involved in creating such simulations, especially the needto efficiently manage variety. We introduce the concept of levels of variety. Then we present our work oncrowd behaviour simulation aimed at interactive real‐time applications such as computer games or virtualenvironments. We define a modular behavioural architecture of a multi‐agent system allowing autonomous andscripted behaviour of agents supporting variety. Finally we show applications of our system in a virtual realitytraining system and a virtual heritage reconstruction. ACM CSS: I.3.7 Three‐Dimensional Graphics and Realism—Animation, I.2.11 Distributed ArtificialIntelligence—Multi‐agent systems

shared virtual environments under three different conditions: (1) voice only, (2) represented by avatars with blinking eyes and lip movements during speech, and (3) represented by avatars that additionally included head movements.Such studies provide valuable information on how people use various non-verbal cues during interaction, and can inform the design of virtual humans.We are grateful to the people who provided detailed reviews of all the papers submitted to this special issue and helped us select these five outstanding examples of research on autonomous virtual humans:

Their contribution is in the field of image segmentation.They observe the possibility of using the overall and class-conditional error rates as criteria for selecting the optimal sampling of the linear and morphological scale spaces.

In this paper, we extend our previous work (Proc. Computer Animation and Simulation, pp. 125-135, Aug. 2000) and propose a muscle model that is suitable for computer graphics based on physiological and anatomical considerations. Muscle motion and deformation is automatically derived from one or several action lines, each action line being deformed by a 1D mass-spring system. The resulting model is fast, can accommodate most superficial human muscles, and could easily be integrated into current modeling packages. Example animations can be found at.

We describe an approach to construct interactive virtual environments, which are suitable for the development of artificial virtual human life simulations. Our main goal is to have virtual human actors living and working autonomously in virtual environments. In our approach, virtual actors have their own motivations and needs, and by sensing and exploring their environment, an action selection mechanism is able to determine at anytime the suitable actions to take. We adapt basic actor motivations and needs to urban situations, where most actions involve interactions with the environment. Thus, a specific technique to define actor-object interactions is used, where pre-defined interaction plans are put inside interactive objects, and just selected during the simulation. We explain the steps taken in order to construct and animate such environments, and we also present a test simulation example.

Our research focuses on animating autonomous virtual humans which are able to take decisions by themselves. We especially address in this paper the technical problem of integrating altogether the physical simulation of agents (represented as virtual humans in a 3D environment) and their behaviours and motivations, driven by a Beliefs, Desires and Intentions architecture. We also explain how goals drive plans, and how an agent can coherently handle concurrent tasks.

present a virtual mobile or moving sculpture system in the third paper.In order to display the virtual mobile interactively, the authors describe the use of the virtual wind model, the constraint dynamics solver and the impulse dynamics solver incorporated in the developed system.The fourth and last paper by G. Besuievsky and X. Pueyo from the University de Girona presents an efficient algorithm to compute animations in radiosity environments.The authors claim that the method is an alternative for computing non-interactive radiosity animations for moderately complex scenarios.

We describe a model for simulating crowds of humans in real time. We deal with a hierarchy composed of virtual crowds, groups, and individuals. The groups are the most complex structure that can be controlled in different degrees of autonomy. This autonomy refers to the extent to which the virtual agents are independent of user intervention and also the amount of information needed to simulate crowds. Thus, depending on the complexity of the simulation, simple behaviors can be sufficient to simulate crowds. Otherwise, more complicated behavioral rules can be necessary and, in this case, it can be included in the simulation data in order to improve the realism of the animation. We present three different ways for controlling crowd behaviors: by using innate and scripted behaviors; by defining behavioral rules, using events and reactions; and by providing an external control to guide crowd behaviors in real time. The two main contributions of our approach are: the possibility of increasing the complexity of group/agent behaviors according to the problem to be simulated and the hierarchical structure based on groups to compose a crowd.

This paper discusses the main issues for creating Interactive Virtual Environments with Virtual Humans emphasizing the following aspects: creation of Virtual Humans, gestures, interaction with objects, multimodal communication.

Optical motion capture provides an impressive ability to replicate gestures. However, even with a highly professional system there are many instances where crucial markers are occluded or when the algorithm confuses the trajectory of one marker with that of another. This requires much editing work on the part of the animator before the virtual characters are ready for their screen debuts. In this paper, we present an approach to increasing the robustness of a motion capture system by using a sophisticated anatomic human model. It includes a precise description of the skeleton's mobility and an approximated envelope. It allows us to accurately predict the 3-D location and visibility of markers, thus significantly increasing the robustness of marker tracking and assignment, and drastically reducing-or even eliminating-the need for human intervention during the 3D reconstruction process.

This paper summarizes recent experiences and case studies to model behaviors of virtual humans in three typical situations: interaction with complex objects, interaction with the user in immersive environments, and social behaviors in crowds.

Current virtual reality technologies provide many ways to interact with virtual humans. Most of those techniques, however, are limited to synthetic elements and require cumbersome sensors. We have combined a real-time simulation and rendering platform with a real-time, non-invasive vision-based recognition system to investigate interactions in a mixed environment with real and synthetic elements. In this paper, we present the resulting system, the example of a checkers game between a real person and an autonomous virtual human to demonstrate its performance.

Presents the VPARK (Virtual Park) system, which includes a networked virtual environment (NVE) system called W-VLNET and an "attraction building system" that is able to create and modify the attractions used in the NVE. Both systems have been developed in the Windows NT environment. The paper outlines the techniques for communication, scene management, facial and body animation, and general user interaction modules. The use of VRML97 and MPEG-4 SHNC is overviewed for the purpose of outlining the compatability of the system with other similar virtual reality systems. The software provides realistic virtual actors as well as sets of high-level actions that are applicable to them in real-time. Related issues on obtaining actor models and animating them in real time are presented. The creation process of an attraction incorporates assembling animation units through a timeline. Using this software, the users are able to bring their own scenario-based applications into a shared virtual environment.

In this paper we present a new framework in Augmented Reality context for rapid evaluation of prototypes before manufacture. The design of such prototypes is a time consuming process, leading t o the need of previous evaluation in realistic interactive environments. We have extended the definition of modelling object geometry with modelling object behaviour being able to evaluate them in a mixed environment. Such enhancements allow the development of tools and methods to test object behaviour, and perform interactions between real virtual humans and complex real and virtual objects.We propose a framework for testing the design of objects i an augmented reality context, where a virtual human is able to perform evaluation tests with an object composed of rea and virtual components. In this paper our framework is described and a case study is presented.

In order to display huge scenes with virtual human inhabitants evolving inside a virtual city, we propose a methodology to create and manage different levels of detail for a well-segmented scene without "re-meshing" the scene during simulation. A database dedicated to urban life simulation, providing data for planning human actions and behaviour, is completed such a way to furnish information about the most adapted displayed representations.

In this paper, we present an integration framework for heterogeneous motion generators. The objective is to outline issues that are currently easily solved in professional post‐processing systems used in film and game production but which cannot be transposed as is to real‐time systems with autonomous agents. We summarise our approach for articulated agent‐modelling and their animation by combining heterogeneous motion generators, such as real‐time motion capturing, key‐framing, inverse kinematics, procedural walking. We propose an agent/action‐oriented framework. Activity properties such as action simultaneity and motion blending, spatial coherence, motion‐flow update schemes, agent attachments, and location corrections, are the main topics handled by our generic animation framework. Numerous examples throughout the paper illustrate our approach and outline encountered problems and solutions or open research directions.

In this paper, we present a new method for solving the Motion Retargeting Problem, by using an intermediate skeleton. This allows us to convert movements between hierarchically and geometrically different characters. An Inverse Kinematics engine is then used to enforce Cartesian constraints while staying as close as possible to the captured motion.

Ohtsuka from the Nippon Telegraph and

Columbia University present a method of computation of swept volumes that permits an arbitrary polyhedral object to be swept through an arbitrary trajectory.The method has an advantage above other methods in terms of ¯exibility and robustness.The authors of the second paper, H. Sun and M. Green from the University of Alberta, present a framework for interactive animation that allows an animator to specify the reactions of the objects to events generated by other objects in the 3D scene and also by the user interacting with it.This approach enables the animators to compose interactively complex scene behaviors.The third paper, by

Rendering and animating in real-time a multitude of articulated characters presents a real challenge, and few hardware systems are up to the task. Up to now, little research has been conducted to tackle the issue of real-time rendering of numerous virtual humans. This paper presents a hardware-independent technique that improves the display rate of animated characters by acting on the sole geometric and rendering information. We first review the acceleration techniques traditionally in use in computer graphics and highlight their suitability to articulated characters. We then show how impostors can be used to render virtual humans. We introduce concrete case studies that demonstrate the effectiveness of our approach. Finally, we tackle the visibility issue.

The paper shows a novel approach to model and control interactive objects for simulations with virtual human agents when real time interactivity is essential. A general conceptualization is made to model objects with behaviors that can provide: information about their functionality changes in appearance from parameterized deformations, and a complete plan for each possible interaction with a virtual human. Such behaviors are described with simple primitive commands, following the actual trend of many standard scene graph file formats that connects language with movements and events to create interactive animations. In our case, special attention is given to correctly interpret object behaviors in parallel; a situation that arrives when many human agents interact at the same time with one same object.

The paper proposes virtual input devices based on collision detection for easy construction of interactive 3D graphics applications which use a motion capture system as a real time input device. Each virtual input device is composed from several collision sensor objects and an actuator object. These objects are software components represented as a visible object which users can manipulate on a computer screen. Each virtual input device has a certain metaphor associated with its role that is determined by location and composition structure of its components. Therefore, it is possible to define various virtual input devices easily only by combining several sensor objects and an actuator object through direct manipulations on a computer screen. The paper presents a realization mechanism and actual examples of virtual input devices.

We show that we can effectively fit complex animation models to noisy image data. Our approach is based on robust least squares adjustment and takes advantage of three complementary sources of information: stereo data, silhouette edges and 2D feature points. We take stereo to be our main information source and use the other two whenever available. In this way, complete head models-including ears and hair-can be acquired with a cheap and entirely passive sensor, such as an ordinary video camera. The motion parameters of limbs can be similarly captured. They can then be fed to existing animation software to produce synthetic sequences.

Performing 3D interactions with virtual objects easily becomes a complex task, limiting the implementation of larger applications. In order to overcome some of these limitations, this paper describes a framework where the virtual object aids the user to accomplish a pre-programmed possible interaction. Such objects are called Smart Objects, in the sense that they know how the user can interact with them, giving clues to aid the interaction. We show how such objects are constructed, and exemplify the framework with an application where the user, wearing a data glove, can easily open and close drawers of some furniture. Keywords Virtual Reality, manipulation, interaction, data glove, virtual objects, virtual environments. 1. INTRODUCTION Virtual Reality (VR) technology has been employed on various different applications, as for example: human factor analysis, navigation in virtual environments, training, visualisation, and design of objects. A common point to all applications i...

Agents in virtual environments require a combination of perception and action to behave in an autonomous way. We extend a software architecture for the management of actions blending, called AGENTlib, with a perception mechanism. The perception system provides a uniform interface to various techniques in the field of virtual perception, including synthetic vision, database access and perception persistency. We describe the framework we designed to efficiently filter valuable information from the scene and we address concerns about computation redundancy and data propagation through multiple filtering modules.

In this paper, we outline the creation of an Informed Environment, dedicated to urban life simulation.We propose methods and tools for creating and providing the information necessary for animating virtual humans in a city using an Informed Environment. The Informed Environment is based on a hierarchical decomposition of a urban scene into Environment Entities providing geometrical information as well as semantic notions, thus allowing a more realistic simulation of human behaviour. In this manner, virtual humans can integrate with a certain kind of urban knowledge.

In networked virtual environments (NVEs), users are represented by their virtual embodiments. The articulated structure of these embodiments introduces a new complexity in the representation and streaming of animations, especially when the number of participants in the simulation increases. This requires real-time algorithms to decrease the networking overhead. The dead-reckoning technique is a way to reduce the required bit rate, and has been used for simple nonarticulated objects in popular NVE systems. We introduce a dead-reckoning technique for articulated virtual human figures, based on the MPEG-4 body animation specification, using Kalman filtering.

We investigate how the movement measurement technologies developed for virtual reality applications can be applied to track in real-time the full body posture of a human being. The accuracy of this information is of definite importance to evaluate the feasibility of complex tasks involving human beings. We present a full body movement measurement approach. It provides a realistic conversion in real-time with a reasonable number of sensors. Associated with the hand movement measurement and correction algorithms we provide a pertinent visual and vibrotactile feedback to the performer.

We present a versatile, behavioral, and rule-based animation system that includes autonomous humanoid actors whose behavior is based on synthetic sensors that are used for perceiving the virtual environment. We combine the following in a consistent approach: L-systems, a behavioral production rule system; a particle system; an acoustic environment model, including a speech recognition module; a virtual life network; and a humanoid library. Together, these systems create a real-time-structured virtual environment that both high-level autonomous humanoids and interactive users can easily share.

Integrating virtual human animation in networked virtual environments (NVEs) has the potential to create severe network load issues. In NVEs, users are represented by their virtual embodiments. The articulated structure of these embodiments introduces a new complexity in the communication, representation and streaming of animations. This might create a significant overhead, especially as the number of participants in the simulation increases. In this paper, we present problems and solutions to efficiently transmit virtual human data over the network.

The authors propose a method to simulate human beings based on anatomy concepts. They believe that the closer the model is to reality, the better the results will be. Using this approach, they are developing a human representation. The model is divided into three different layers and is presented in three steps: the rigid body conception from a real skeleton, the muscle design and deformation based on physical concepts, and the skin generation. Integration aspects and results are also presented.

In this paper we propose a method to simulate muscle deformation in real-time, still aiming at satisfying visual results; that is, we are not attempting perfect simulation, but building a useful tool for interactive applications. Muscles are represented at 2 levels: the action lines and the muscle shape. The action line represents the force produced by a muscle on the bones, while the muscle shapes used in the simulation consist of a surface based model fitted to the boundary of medical image data. The algorithm to model muscle shapes is described. To physically simulate deformations, we used a mass-spring system with a new kind of springs called "angular springs" which were developed to control the muscle volume during simulation. Results are presented as examples at the end of the paper.

The authors present a novel approach to participant embodiment in networked collaborative virtual environments. The embodiment approach integrates live video into 3D objects for a hybrid participant representation. They implemented their ideas in a Networked Collaborative Virtual Environment system, VLNET and investigated network and rendering issues in comparison with virtual human participant embodiment. The paper presents two distinct case studies demonstrating their ideas. The first one is a tele-teaching application, in which they investigate a shared environment with virtual humans and hybrid embodiments. The second one presents a distributed augmented reality application, in which participants share a mixed environment with real and virtual elements.

Introducing seemingly autonomous virtual beings into virtual environments to co-habit and collaborate with us is a continuous challenge and source of interest. Latest proof of human excitement for virtual life is the current worldwide craze for electronic pets that must be fed and cared for lest they develop a bad character or die. Even more interesting is the inclusion of autonomous actors in networked collaborative virtual environments (NCVEs). They provide a meeting place for people from different geographical locations and virtual beings. In NCVEs one doesn't see correspondents, only their graphical representations in the virtual world, which is the same as for the virtual ones-therefore the communication with virtual beings can come naturally. There is no single solution to the simulation of autonomous behavior. This is an ongoing research topic. Therefore it is interesting to provide an open NCVE system for easy interfacing with various implementations of autonomous behavior. In this way, the system can serve as an application platform with existing algorithms, as well as a research testbed for new autonomous behavior algorithms. The paper studies the requirements for such an open interface and, based on this study, presents an implementation within the Virtual Life Network (VLNET) system. Results are presented in terms of two case studies. A simple one implementing a dumb servant character and a more complex one connecting VLNET with the autonomous agent program Eliza (Weizenbaum, 1966).

This paper presents a crowd modelling method in Collaborative Virtual Environment (CVE) which aims to create a sense of group presence to provide a more realistic virtual world. An adaptive display is also presented as a key element to optimise the needed information to keep an acceptable frame rate during crowd visualisation. This system has been integrated in the several CVE platforms which will be presented at the end of this paper. 1.1 Keywords Autonomous agents, virtual crowds, virtual environments.

There is a large body of research on motion control of legs in human models. However, they require specification of global paths in which to move. A method for automatically computing a global motion path for a human in 3D environment of obstacles is presented. Object space is discretized into a 3D grid of uniform cells and an optimal path is generated between two points as a discrete cell path. The grid is treated as graph with orthogonal links of uniform cost. A* search method is applied for path finding. By considering only the cells on the upper surface of objects on which human walks, a large portion of the grid is discarded from the search space, thus boosting efficiency. This is expected to be a higher level mechanism for various local foot placement methods in human animation.

This issue contains three papers.In the first paper, Akio Doi and Takayunki Itoh from the State University of New York at Stony Brook propose a novel formfactor calculation algorithm for acceleration radiosity solutions in complex environments.They also parallelize their approach by dividing a hemisphere-base into regions and assign a region to each processor.The second paper by Christopher Betts from Monash University in Melbourne, Australia, introduces a number of simple techniques that allow very fast rendering of multiple independently moving objects under the conditions of special relativity.In addition to geometric rendering, a simplified lighting model is presented, which allows the apparent colour changes of objects to be observed, along with changes in the apparent direction of illumination.In the third paper, Xuguang Wang and Jean Pierre Verriest from INRETS-LESCO in Bron, France, describe an inverse kinematic algorithm to predict arm reach postures based on the criterion of minimization of the norm of joint angular velocities.The main advantage of the proposed method is that it can take into account the non-linearity of the shoulder joint limit in a direct and easy way.

This issue contains six papers.Two of them are regularly

Interaction between real and virtual humans covers a wide range of topics from creation and animation of virtual actors to computer vision techniques for data acquisition from real world. We discuss the design and implementation of an augmented reality system which allows investigation of different real/virtual interaction aspects. As an example we present an application to create real time interactive drama with real and virtual actors.

We present an animation interface designed to conveniently control the motion capture process. The transition of performer's hand gestures tracked by a dataglove is recognized for software remote control. An intuitive camera metaphor allows one to specify the viewpoint location using the magnetic sensors strapped to the performer's head. The human motion capture is based on the Anatomical Converter, a toolkit to convert sensor measurements into human anatomical rotations in real time. An improved human motion capture technique, the multi-joint control, is introduced.

We propose a model of a tennis game simulation with synthetic actors as players and a referee. The behaviour of these actors is based on their synthetic vision and audition. Physical modeling of the ball dynamic and sound rendering enhance realism. An interactive user can also play against a synthetic actor by using a Space Ball.

The recognition of daily human activities is a decisive interface component for more intuitive virtual reality (VR) interactions. In this paper, we describe a hierarchical model of body actions based on fine-grained action primitives. The associated recognition algorithm allows on-the-fly identification of simultaneous actions. Measurements highlight robustness to participants' variability and high detection rates when using the full potential of the action model. An example illustrates an interaction with a virtual character driven by the participant's action recognition.

Real-time animation of virtual humans requires a dedicated architecture for the integration of different motion control techniques running into so-called actions. In this paper, we describe a software architecture called AGENTlib for the management of action combination. Considered actions exploit various techniques from keyframe sequence playback to inverse kinematics and motion capture. Two major requirements have to be enforced from the end user viewpoint: first, that multiple motion controllers can control simultaneously some parts or whole of the virtual human, and second, that successive actions result in a smooth motion flow

Navigation within the scope of a Networked Collaborative Virtual Environment (NCVE) using an articulated body representation is mores complex then just moving the viewpoint based on user input.In such context, navigation englobes problems such as mapping of user's actions on the embodiment and body constraints in addition to the usual ones such as universal support for different devices and global motion constraints.We take a broader look at the problems, clasify them and present a solution for navigation in NCVEs.Basic navigation involves using some input device to control walk-through or fly-through motion.In the context

Complex virtual human representation provides more natural interaction and communication among participants in networked virtual environments, hence it is expected to increase the sense of being together within the same virtual world. We present a flexible framework for the integration of virtual humans in networked collaborative virtual environments. A modular architecture allows flexible representation and control of the virtual humans, whether they are controlled by a physical user using all sorts of tracking and other devices, or by an intelligent control program turning them into autonomous actors. The modularity of the system allows for fairly easy extensions and integration with new techniques making it interesting also as a testbed for various domains from “classic” VR to psychological experiments. We present results in terms of functionalities, example applications and measurements of performance and network traffic with an increasing number of participants in the simulation.

Pacific Graphics '95, the third international conference on Computer Graphics and its Applications, was held on 21-24 August 1995, in Seoul, Korea.Following on the success of the two previous conferences: Pacific Graphics '93 (Seoul, Korea) and Pacific Graphics '94 (Beijing, China), we received 62 submissions from 22 different countries all over the world and, after peer review, selected 24 papers for publication in the conference proceedings: Computer Graphics and Applications, published by World-Scientific, Singapore.(The proceedings also include 10 invited papers.)The four papers presented in this special issue were judged by the programme committee members to be the best of the 24 selected papers presented at the conference.Each of the four papers was further reviewed by experts in the respective research area and the papers were further improved on the basis of comments received.The first paper, by Kim and Elber, presents a symbolic approach to generate blending surfaces between two polynomial and/or rational surfaces.Using a purely symbolic technique, the authors demonstrate how to compute various cross boundary tangent vector fields on each rail curve and represent the blending surfaces as polynomial or rational surfaces.The next paper, by Sun, Wang and Chin, presents a 3D morphing algorithm which transforms one polyhedral model into another.Considering each polyhedron as a graph representing vertex adjacencies, the authors develop a simple and elegant method which generalizes the 2D polygonal morphing algorithms of Sederberg to a 3D polyhedral morphing algorithm.The third paper, by Lee and Shin, presents an efficient ray casting algorithm for terrain rendering from DTMs (digital terrain models).The authors introduce a formal analysis to vertical ray coherence.Based on this analysis, they propose a new technique which covers the entire image plane with non-parallel ray lines.This

proposes methods to generate a visual simulation of forest scenery.Several problems have to be solved: generation of vegetation, representation of trees, silmulation of color changes of leaves, and rendering of numerous trees.The paper emphasizes the last problem.The method proposed is based on 3D textures.The second paper by David E Breen from Computer Graphics Lab, California Institute of Technology, USA shows how the concept of cost minimization for modeling geometrical constraints may be used for several 3D animated modeling tasks.Three application examples are included to demonstrate tha approach: path planning and motion generation for animated actors, generation of geometrically deformed models for visualization, and physically based modelling of woven cloth.

We present a posture design paradigm for the positioning of complex characters. It is illustrated here on human figures. We exploit the inverse kinetics technique which allows the center of mass position control for postures with either single or multiple supports. For the multiple support case, we introduce a compatible flow model of the supporting influence. With this approach, we are able to handle continuous modification of the support distribution. By construction, inverse kinetics presents the same control architecture as inverse kinematics, and thus, it shows equivalent computing cost and similar intuitive concepts. Furthermore, inverse kinetics for the center of mass and inverse kinematics for fixed end effecters can be combined to generate a posture displaying static balance, goal oriented features, and an additional gravity optimization.

The paper presents a model of nonverbal communication and interpersonal relationship between virtual actors. Nonverbal communication improves their believability. They react not only to the presence of the other actors but also to their postures. Furthermore, their interpersonal relationships me affected by the issue of social interactions. To avoid homogenous group behaviors, each actor is set with a different character profile. We present an application of this model to create actors involved in social interactions in a virtual public garden. The animation of virtual actors is based on the library AGENTlib which is dedicated to the management of agent entities able to coordinate perception and action.

We present a formal theory of a behavioral L-system and describe as application a real time structured L-system interpreter. The behavioral L-system is a timed, conditional, stochastic, parametric and environmentally sensitive L-system which allows besides the modeling of plant and fractal development the description and animation of autonomous actors completely defined by production rules. A virtual environment including geometric objects, force fields and sounds and the behaviors of actors can be defined using the same formalism of the behavioral L-systems.

Virtual Actors now play an important role in computer-generated films, Virtual Environments, Telecooperative work, and multimedia. In order to make these actors realistic, it is essential to represent their body shape during the motion. In this paper we present different methods for representing realistic deformations for virtual humans with various characteristics: sex, age, height, weight. Our methods based on a combination of metaballs and splines could be applied to frame-by-frame computer generated-films and Virtual Environments. Several examples are presented: autonomous actors, animation based on flock of birds, networked Virtual Environments.

The manipulation of a virtual object by means of a digital glove is a tedious task for repetitive position and orientation adjustments. In this paper we try to overcome the lack of force feedback of general purpose digital gloves. We propose a solution based only on the interpretation of instantaneous hand posture variations. From this knowledge, a virtual contact model analog to the Coulomb law allows to evaluate the instantaneous nature of the contact, firm or sliding, between virtual sensors attached to the fingers and the virtual object. Although no force feedback is supplied, we are able to derive a visual restitution consistent with the user manipulative intentions while respecting the integrity of solid interaction with friction.

Abstract Availability of Visible Human Dataset (VHD)has provided numerous possibilities for its exploitation in both medical applications and 3D animation. In this paper, we present our interactive tools which enable extraction of surfaces for different organs, including bones, muscles, fascia, and skin, from the VHD. The reconstructed surfaces then are used for defining the inter‐relationship of organs, a process we refer to as topological modeling. A data base is constructed, which encapsulates structural, topological, mechanical and other relevant information about organs. A 3D interactive tool enables the building and editing of this data base. Such a data base can later be used for different applications in fields such as medicine, sports, education, and entertainment.

In the first paper of this issue, Patrizia Palamidese from CNR CNUCE in Pisa, Italy, presents a camera operator-orientated interface which incorporates camera motion rules derived from traditional film practices.The paper also describes an interactive tool for planning camera shots within any 3D geometric world.The second paper, by Norishige Chiba and Ken Ohshida from Iwate University, Kazunobu Muraoka from Morioka College, and Nobuji Saito from Tohoko Institute of Technology in Japan, proposes a method for the visual simulation of leaf arrangement and autumn colours.The paper presents simulation methods based on the estimation of the amount of sunlight and the brightest direction of each part of every leaf.In the third paper, Myung-Soo Kim and Kee-Won Nam from Postech in South Korea, describe an algorithm for the Hermite interpolation of solid orientations with circular blending quaternion curves.The complete algorithm is described in pseudocode as an appendix to the paper.The last paper, by Hanqiu Sun from the University of Winnipeg in Canada, analyses the complexities of modular specification and processing in a general animation scene context, based on the concept of relations, its modelling framework, and state control hierarchies.

This paper presents techniques and tools for creating and animating virtual actors in real scenes. Several problems are explained: real objects hidden by virtual actors and virtual actors hidden by real objects, collision detection between the virtual actor and the real environment correspondence between the real and the virtual cameras, casting shadows of the virtual actors on the real world. Case studies are presented like the virtual actress Marilyn walking with real people on a real street or sitting down on a real chair.>

Abstract Collision detection tests between objects dominate run time simulation of rigid body animation. Traditionally, hierarchical bounding box tests are used to minimize collision detection time. But the bounding boxes do not take shapes of the objects into account which results in a large number of collision detection tests. We propose an adaptive spatial subdivision of the object space based on octree structure to rectify this problem. We also present a technique for efficiently updating this structure periodically during the simulation.

Abstract We describe the HUMANOID environment dedicated to human modeling and animation for general multimedia, VR, and CAD applications integrating virtual humans. We present the design of the system and the integration of the various features: generic modeling of a large class of entities with the BODY data structure, realistic skin deformation for body and hands, facial animation, collision detection, integrated motion control and parallelization of computation intensive tasks.

Abstract We present an overview of some principles of synthetic vision and audition for digital autonomous actors in virtual worlds. After a short review of the state‐of‐the‐art we focus on some aspects of synthetic vision and virtual world constraints. Then, we present a simple real time structured sound renderer. This sound renderer is used as audition channel for synthetic and real actors and synchronized sound track generator for video film productions.

from Middlesex University proposes a method of implicitly storing particles for modelling fluid flow.The paper is illustrated with the modelling of large waterfalls.Dominique Bechmann and Nicolas Dubreuil from the UniversitC Louis Pasteur in Strasbourg, France, introduce an order-controlled method for building an animation by breaking it up into a list of deformations composed of a set of constraints.In addition to each constraint, the user has to control the size and the shape of the deformed area as well as the shape of the deformation.The third paper is an application paper; this means that it does not propose original methods, but a complete and functional application.In this paper, Sudhanshu Kumar Semwal and Paul Gene Swann from the University of Colorado in the U.S.A., apply a ray casting technique to the flow visualization data using linear and B-spline hyperpatch interpolation.

Larry Gtitz and James Hahn from The George Washington University present an approach to articulated figure motion in which motion tasks are defined in terms of goals and ratings.They use genetic programming to automatically derive control programs for the agents which achieve the goals.

The second international conference on Computer Graphics around the Pacific area-Pacific Graphics '94-was held in August 1994 at Beijing, China.In order to share the contributions from the authors in this conference and to improve the mutual communication among researchers and developers with common interests, four papers have been selected from this conference for publication in this special issue.In recent years, the animation of the human body has been a hot topic for research.The paper 'A Dynamic Wrinkle Model in Facial Animation and Skin Ageing' describes a dynamic model to simulate expressive wrinkles in 3D facial animation and skin ageing.In this model, action units in the facial action coding system are used to define facial expressions, and the skin is specified as a nonlinear and inelastic material.The system produces distinctive expressive wrinkles corresponding to different faces with the dynamic model.Generating an image for high qyality with volume rendering is extremely expensive and far from interactive.The time complexity of the volume rendering is determined by the number of cells.In the paper 'Subvolume Projection: A Full Exploitation of Function Coherence for Volume Rendering', the spatial coherence of a function distribution is fully exploited by partitioning a volume into a number of subvolumes.Each subvolume can be considered as containing a single material and treated as the smallest unit instead of cells in the processing.Theoretical analysis and the experimental results show that the new approach improves image quality and reduces rendering time.Fractal geometry provides an outstanding mathematical tool for simulating natural phenomena.However, the recursive process of stochastic modelling in generating random fractals results in difficult problems in the rendering.In the paper on 'A Radiosity Solution for Random Fractal Surfaces', a radiosity solution for rendering random fractals is given.The recursive process of fractal generation is naturally incorporated into the progressive refinement procedure of radiosity solution.Some examples show that this method is efficient.In the paper 'Modelling Radiative Properties of Light Sources and Surfaces', a

Abstract This paper describes a dynamic model to simulate expressive wrinkles in 3D facial animation and skin ageing. A skin surface is defined that can slide over an underlying layer, which constrains the surface by a spring force that simulates the connective fat tissue between them. Muscle masks are constructed to characterize the muscular contractions that provide the facial movement. Skin deformation is simulated through an elastic process assembled with visco and plastic units. By adjusting parameters for this physically based model, distinctive wrinkles for different faces can be generated.

In this paper, we define the concept of digital actors and show their importance in the future interactive digital television and multimedia. We discuss the applications of these digital actors in the new multimedia services especially for training and education. We summarize the main techniques to create and control these digital actors and emphasize the importance to develop new tools for the control and the autonomy of these actors. An integrated and functional system for the animation of digital actors is presented. In particular, we describe the integration of motion control techniques, autonomy based on synthetic sensors and facial communication.>

The scope of this paper is to propose a system for the automatic derivation of a human curved walking trajectory from the analysis provided by its synthetic vision module. The study context is a planar environment with still and sparse foothold locations. A general methodology associates the two low-level modules of vision and walking with a planification module which establishes the middle term path from the knowledge of the visualized environment. The planification is made under the constraint of minimizing the distance, the speed variation and the curvature cost. Moreover, the planification may trigger the alternate walking motion whenever the decreasing in curvature cost is higher than the associated increasing in speed variation cost due to the corresponding halt and restart. Finally, the characteristic of the next step location is derived in the context of a constant velocity walking motion along a circular trajectory.>

Abstract In the computer animation field, the interest for grasping has appeared with the development of synthetic actors. Based on a grasp taxonomy, we propose a completely automatic grasping system for synthetic actors. In particular, the system can decide to use a pinch when the object is too small to be grasped by more than two fingers or to use a two‐handed grasp when the object is too large. The system also offers both direct and inverse kinematics to control the articulations. In order to ensure realistic looking closing of the hand, several of the joints are constrained. A brief description of the system and results are also presented.

The paper describes the VB2 architecture for the construction of three-dimensional interactive applications. The system's state and behavior are uniformly represented as a network of interrelated objects. Dynamic components are modeled by active variables, while multi-way relations are modeled by hierarchical constraints. Daemons are used to sequence between system states in reaction to changes in variable values. The constraint network is efficiently maintained by an incremental constraint solver based on an enhancement of SkyBlue. Multiple devices are used to interact with the synthetic world through the use of various interaction paradigms, including immersive environments with visual and audio feedback. Interaction techniques range from direct manipulation, to gestural input and three-dimensional virtual tools. Adaptive pattern recognition is used to increase input device expressiveness by enhancing sensor data with classification information. Virtual tools, which are encapsulations of visual appearance and behavior, present a selective view of manipulated models' information and offer an interaction metaphor to control it. Since virtual tools are first class objects, they can be assembled into more complex tools, much in the same way that simple tools are built on top of a modeling hierarchy. The architecture is currently being used to build a virtual reality animation system

Abstract There are basically four problems to solve in order to produce realistic animated synthetic actors with hair: hair modeling and creation, hair motion, collision detection and hair rendering. This paper describes a complete methodology to solve these basic four problems. We present how hair styles may be designed with our Hair Styler module. Then we survey the animation model and emphasize a method of collision processing. Finally, we explain how hair may be rendered using an extension of a standard ray‐tracing program. We also show applications of our synthetic actors with various hair styles and different styles of mustaches and beards.

This issue contains five research papers covering various aspects of visualization and animation.The first paper is a typical visualization paper.Craig Liddell and Deren Hansen from New Mexico State University present their research in visualizing and modelling fungal and plant root development and interactions in the soil.The paper shows the power of the synthetic approach, using inductive and deductive visualization, for addressing difficult experimental and conceptual issues in soil microbial ecology.

In the first paper of this issue Jintae Lee and Tosiyasu Kunii from the University of Tokyo, Japan, present a model of a system that is capable of translating text from a natural language into animated sign language.The technique is useful to facilitate communication between the hearing impaired and those with normal speaking capabilities.A hand motion coding method is applied to the hand motion representation.In the second paper, Stephane Jimenez, Annie Luciani and Olivier Raoult, from the Institut d'hformatique et de Mathkmatiques Appliquies de Grenoble, France, show how physical models and dynamic simulation tools can be used for amending and completing a nomimal motion plan provided by a classical geometric path planner.They formulate the motion planning problem through the concepts of generalized obstacle and physical target.Volker Kuhn and Wolfgang Muller from Interactive Graphics Systems Group in Darmstadt, Germany, describe a new approach for the development of flexible, efficient methods and techniques to control multibody systems.They introduce highlevel concepts represented by agents, environments and controllers based on and supported by the object-oriented paradigm.

This issue contains three research papers, one on a global illumination model and two on computer animation.First

This paper discusses the use of physics-based models for animating clothes on synthetic actors in motion.In our approach, cloth pieces are fist designed with polygonal panels in two dimensions, and are then seamed and attached to the actor's body in three dimensions.After the clothes are created, physical properties are simulated and then clothes are animated according to the actor's motion in a physical environment.We describe the physical models we use and then address several problems we encountered.We examine how to constrain the elements of deformable objects which are either seamed together or attached to rigid moving objects.We also describe a new approach to the problem of handling collisions among the cloth elements themselves, or between a cloth element and a rigid object like the human body.Finally, we discuss how to reduce the number of parameters for improving the interface between the animator and the physics-based model.

Abstract A new approach for the animation of articulated figures is presented. We propose a system of articulated motion design which offers a full combination of both direct and inverse kinematic control of the joint parameters. Such an approach allows an animator to specify interactively goal‐directed changes to existing sampled joint motions, resulting in a more general and expressive class of possible joint motions. The fundamental idea is to consider any desired‐joint space motion as a reference model inserted into the secondary task of an inverse kinematic control scheme. This approach profits from the use of half‐space Cartesian main tasks in conjunction with a parallel control of the articulated figure called the coach‐trainee metaphor. In addition, a transition function is introduced so as to guarantee the continuity of the control. The resulting combined kinematic control scheme leads to a new methodology of joint‐motion editing which is demonstrated through the improvement of a functional model of human walking.

Abstract This paper describes interactive facilities for simulating abstract muscle actions using Rational Free Form Deformations (RFFD). The particular muscle action is simulated as the displacement of the control points of the control‐unit for an RFFD defined on a region of interest. One or several simulated muscle actions constitute a Minimum Perceptible Action (MPA), which is defined as the atomic action unit, similar to Action Unit (AU) of the Facial Action Coding System (FACS), to build an expression.

This issue, the first with a new look, contains five research papers.The first paper is a typical visualization paper.Christopher Giertsen from the IBM Bergen Scientific Centre describes an implementation of a volume visualization concept where several modelling and rendering techniques can be applied in any combination, mainly bounded by the creativity of the user.

This issue contains five research papers covering various aspects of Visualization and Animation.In the first paper, by Tatsuo Miyazawa and Koji Koyamada from Tokyo Research Laboratory, IBM Japan, an integrated rendering algorithm for visualizing 3D volumetric and geometric data is proposed.The authors explain how to extend a volume rendering algorithm based on ray-tracing so that it can handle both 3D volumetric

from the Swiss Federal Institute of Technology present an indexed bibliography on Computer Animation.With over 600 references, this bibliography aims to be the most complete to-date.Christian Munkel and Dieter Heermann from the University of Heidelberg present an interesting paper about the visualization of polymer systems.This paper is a typical paper that combines computer simulation and three-dimensional scientific visualization.The authors discuss two important issues in this kind of research: realistic appearance of images and execution time.The last paper describes an interactive, electronic museum where users can move from room to room, and select any exhibit in a room for more detailed examination.One of the most interesting aspects of this research is the new method for navigating through a prerendered 3D space and interacting with objects in that space.

The evolution of computer animation in the last six years has been spectacular. Several outstanding computer-generated films have been produced and have received international awards. Owing to the evolution of graphics hardware, the quality of rendering now allows the simulation of subtle lighting effects or textures. But, also new computer animation techniques appeared as important alternatives to the traditional keyframe methods. The bibliography aims to be the most complete to date. It shows that computer animation is no longer a collection of tricks just for showing special effects. It has become a mature and distinct area with its own techniques and methods

describes a tool for computer-assisted design of visualizations and a technique for monitoring a computational process in a non-invasive fashion.In the second paper, Richard Parent from Ohio State University, discusses the issues relating to the shape transformation problem.He presents a new algorithm for computing the transformation of one shape into another.The paper is interesting, because it solves the problem at the object level rather than at the image level as in the well-known morphing technique.The algorithm establishes a mapping between areas of the objects such that adjacency relationships are preserved.

Abstract A technique is described for adding natural‐looking hair to standard rendering algorithms. Using an explicit hair model, in which each individual hair is represented by a three‐dimensional curve, the technique uses pixel blending combined with Z‐buffer and shadow buffer information from the scene to yield a final anti‐aliased image with soft shadows. Although developed for rendering human hair, this technique can also be used to render any model consisting of long filaments of sub‐pixel width. The technique can be adapted to any rendering method that outputs Z‐buffer and shadow buffer information and is amenable to hardware implementation.

Abstract This paper presents an innovative way of animating actors at a high level based on the concept of synthetic vision. The objective is simple: to create an animation involving a synthetic actor automatically moving in a corridor avoiding objects and other synthetic actors. To simulate this behaviour, each synthetic actors uses a synthetic vision as its perception of the world and so as the unique input to its behavioural model. This model is based on the concept of displacement local automata (DLA), which is similar to the concept of a script for natural language processing. A DLA is an algorithm that can deal with a specific environment. Two DLAs, called follow‐the‐corridor and avoid‐the‐obstacle, are described in detail.

This paper presents a method for combining image synthesis and modeling based on a finite element method (FEM) to get realistic intelligent images. FEM is used for modeling both elastically and plastically deformations of objects, and impacts with or without penetration between deformable objects. The concept of deformable objects is applied to human flesh to improve the behavior of synthetic human grasping and walking. The paper also discusses the introduction of this method in an animation system based on the concept of "intelligent" synthetic actors with automatic motion control performed using A.I. and robotics techniques. In particular, motion is planned at a task level and computed using physical laws.

This paper addresses the problem of simulating deformations between objects and the hand of a synthetic character during a grasping process. A numerical method based on finite element theory allows us to take into account the active forces of the fingers on the object and the reactive forces of the object on the fingers. The method improves control of synthetic human behavior in a task level animation system because it provides information about the environment of a synthetic human and so can be compared to the sense of touch. Finite element theory currently used in engineering seems one of the best approaches for modeling both elastic and plastic deformation of objects, as well as shocks with or without penetration between deformable objects. We show that intrinsic properties of the method based on composition/decomposition of elements have an impact in computer animation. We also state that the use of the same method for modeling both objects and human bodies improves the modeling both objects and human bodies improves the modeling of the contacts between them. Moreover, it allows a realistic envelope deformation of the human fingers comparable to existing methods. To show what we can expect from the method, we apply it to the grasping and pressing of a ball. Our solution to the grasping problem is based on displacement commands instead of force commands used in robotics and human behavior.

Abstract Several ideas and experiments are presented for the creation and realistic animation of three‐dimensional scenes involving human beings conscious of their environment. The various approaches should allow the intelligent creation of human beings using prototypes and generate their animation based on mechanics, artificial intelligence and robotics. This paper discusses the problems involved in three major steps of the simulation of human beings: the creation of the human shapes, the motion of the human skeleton, and the deformation of the surfaces. Several examples are presented illustrating positional constraints, dynamics, behavioural animation and finite element theory.

This paper describes a method for creating and animating a synthetic actress. It emphasizes the methodology used to generate realistic images and motions. In particular, points which are often ignored in the literature are explained in detail: for example, the planning and preparation of models for digitizing, composition, skeleton installation and the animation process itself.

A particle system, as defined by Reeves, is a collection of particles that together represent a fuzzy object. Over a period of time, particles in the system are born, move, change and die. We have introduced interactive control of procedural models into our extensible director-oriented animation system MIRANIM. With this approach, a user may define his/her own evolution laws in particle systems. Systems may be initialized by interactive commands and are then updated by animation blocks, and the laws may return any state variables. Unlike Reeves' work, particle systems may intersect with other surface-based modeling primitives. Our rendering method is based on a scanline A-buffer algorithm, which is an extension of the processing of translucent polygons. This approach proved to be particularly useful for modelling objects destroyed by a fire with the presence of a wind.

Abstract Recent developments in hardware and software have led to the production of complex computer‐generated images and films. Sophisticated algorithms like ray‐tracing, fractals or particle systems allow the generation of very realistic natural scenes. However, the design of images and films is still a painful task for designers, because of the inadequacy of person‐machine interfaces. A large number of parameters is necessary to build objects (curves, surfaces) to define their properties (orientation, size, colour, transparency, texture, reflectance), to specify the viewing angle, to control the lights and shadows, to define and synchronize motions. The technology of artificial intelligence and more specially knowledge engineering makes possible the development of intelligent human‐machine interfaces for image synthesis and animation. Designers may communicate with design and animation systems using natural language. Basic geometric rules may be given to the computer, making it an expert in 3D geometric modeling. Languages based on the concept of frame simplify the intelligent description of complex objects. Expert systems allow the designer to specify the conditions of an image using goal‐directed specifications for cameras and lights. Scripts and actors are particularly appropriate for the description of motions; the impact of these concepts on 3D computer animation is considerable. Finally, the complex problem of animation of articulated bodies may be solved using knowledge‐based animation. Examples are presented using our new language EXPERTMIRA. This language is based on MIRA and PROLOG and incorporates concepts of artificial intelligence, image synthesis and animation.

An innovative kind of procedural model for computer animation is presented in the form of subactor data types. When a subactor data type is defined, many instances of this type may be defined. Each occurrence has the same parameters, but the animation laws applied to the parameters may be completely different. These occurrences of subactors as well as the associated animation laws are controlled in a user-friendly way. Several subactors may be dependent on an actor which may also be globally animated. Subactors based on Coons surfaces and beta-splines surfaces are discussed. Several examples are presented including a clock, a robot and a mask.

Abstract This paper presents a method of colouring pictures by using three kinds of gradation techniques: gradation from a figure to a point, gradation from a figure to a line segment and gradation from a figure to another figure. Intermediate figures are computed by homothesis or interpolation. The gradation is obtained by colouring these intermediate figures. The colours are simulated by using programmed pattern. This approach has allowed us to produce realistic images with a hardware device that is not very good for these types of applications. because of its restricted intensity and colour capabilities. Colour distribution algorithms and gradation techniques are explained in detail. A few examples with shading and texture are shown.

Abstract GRAFANA is an interactive program, which allows the user to produce drawings based on data stored on a disk file. The major advantage and originality of the system is that the user can interactively determine the visual effect of a drawing and immediately see it on the screen. Moreover, any drawing produced by GRAFANA can still be edited by a generalpurpose graphics editor. This system allows the user to obtain precisely the right drawing for any book, paper or report. GRAFANA has been implemented in MIRA‐2D, a graphical Pascal extension. It is available for different machines and kinds of graphical devices.

The MIRALIB library is a powerful graphical library which may be used with MIRA-2D, a graphical PASCAL extension as well as with the standard PASCAL language. MIRALIB includes figure algebra routines, figure measure functions, figure recognition predicates, image transformations as fitting or clearing and animation primitives. The most unusual primitives are presented with the help of a few examples.

Abstract The goal of this paper is to present a graphical Pascal extension, named MIRA. This extension gives the user the means of defining and using specific graphical types. A complete vector arithmetic has been developed and a new structured type has been introduced: the figure type. Instructions to create and delete figures are discussed and it is shown how the graphical types can be used as other Pascal types. The implementation is carried out by a portable Pascal preprocessor.

It is more attractive for students to learn programming concepts like control structures, data structures or recursion by the means of examples based on graphical objects. The use of a graphical PASCAL extension is a well-suited way of realizing this goal. In particular, we emphasize the use of interactive graphical input-output, graphical types and data structures bases on graphical types. Typical examples are arrays of circles or linked lists of figures entered by the student.

Abstract graphical data types have been de signed and implemented as an extension of the PASCAL language. This extension gives the user a way of defining and using specific graphical types. It is shown how these types can be used as other PASCAL types. The concept of image transformation is also presented. This extension has been realized by a preprocessor and major features of the implementation are discussed.

Two of the most demanding subjects in a Computer Science Curriculum are Compiling Techniques and Databases. In both courses, a major problem is: what should be the main project in the laboratory?. Since 1974, we have had students at various universities write compilers (2) in such a course. In each case, a complete compiler has been implemented. We have tried to establish a direct connection between the Compiling Techniques Course and the Databases Course because both can be selectively chosen by the same students.This paper is divided into three parts: first, we outline the content of each course and the relationship existing between them; secondly, we analyze the criteria for language selection with regards to both courses (also with respect to methodology and to structured programming); third, we discuss the language and illustrate it using some examples.