In this paper, we extensively evaluate the effectiveness of using a user's social media activities for estimating degree of depression. As ground truth data, we use the results of a web-based questionnaire for measuring degree of depression of Twitter users. We extract several features from the activity histories of Twitter users. By leveraging these features, we construct models for estimating the presence of active depression. Through experiments, we show that (1) features obtained from user activities can be used to predict depression of users with an accuracy of 69%, (2) topics of tweets estimated with a topic model are useful features, (3) approximately two months of observation data are necessary for recognizing depression, and longer observation periods do not contribute to improving the accuracy of estimation for current depression; sometimes, longer periods worsen the accuracy.

We propose a portable umbrella-shaped device called U-brella as an application of “vibrationizing” information. Vibrationizing is a term coined to mean the transformation of various types of information into a vibration. Funbrella is an earlier version of U-brella that allows users to experience rain with vibrations, while U-brella offers them the ability to feel ultraviolet rays by converting them into vibration. We first conceptualized the implementation of U-brella: improving the mechanism of Funbrella's vibration generator to make it lighter and easier to carry. Then we conducted a user study to confirm the efficiency of our system's vibrationizing and users' impressions of U-brella. The results showed that the participants easily perceived the amount of ultraviolet rays and that they really felt the rays pour down upon their heads with U-brella.

This paper describes Ambient Party Room, which is a room-shaped information environment for party situations. This system estimates the conversation states by measuring participants' nonverbal cues and displays various types of information to stimulate the conversation. In this study, we reconstructed the system architecture from an early prototype and newly examined several types of information stimulus using a floor display, wall displays, and speakers. We conducted an experiment in which six participants talked freely in Ambient Party Room. Results showed that both profile-based information stimulus and feedback information of participants' behaviors contributed to their activated conversations.

In this paper, we investigate the effectiveness of the records of user's activities in Twitter, which is a popular microblogging site, for estimating his/her depressive tendency. We construct multiple regression model to estimate user's depressive tendency from the frequencies of words used by the user. We perform experiments to estimate participants' depressive tendencies using the constructed regression model. Our experimental results show that there exists medium positive correlation (correlation coefficient r ≃ 0.45) between the Zung's Self-rating Depression Scale, which is a popular measure for estimating depressive tendency, and estimated score obtained from the regression model.

We propose a room-shaped information environment called Ambient Suite that enhances interpersonal communication. In Ambient Suite, the room itself works as both sensors to estimate the conversation states of participants and displays to present information to stimulate conversation. This paper introduces an implementation assumed standing-party situations as a typical use case of Ambient Suite. From the result of user study using its implementation, we confirmed that our system adequately encouraged participant conversations.

We propose a furry and scalable multi-touch display called the “FuSA2Touch Display.” The furry type of tactile sensation of this surface affords various interactions such as stroking or clawing. The system utilizes plastic fiber optic bundles to realize a furry-type texture. The system can show visual feedback by projection and detects multi-touch input. We implemented a 24-inch display, and found that our implemented display encourages users to interact with it in various actions.

Recently, laser-based people-tracking systems have received increasing attention for their ability to localize human subjects precisely in crowded situations. However, in a real environment, there exist many kinds of moving objects other than people, and previous methods have focused only on humans. To design a more sophisticated system, it is necessary to distinguish humans from observed objects and recognize their individual condition-for example, the kind and amount of belongings they are carrying. However, in previous methods using 2D laser range finders (LRFs), it proved difficult to recognize the type of target since all sensors observe a common horizontal plane and only the 2D contours of their targets. In this study, to recognize the type of target, we observe the 3D shapes of objects moving in their environment by installing LRFs with an angle of inclination. So far, in the area of 3D modeling, LRFs have been used to construct 3D models of static objects by moving the sensor and registering multiple views. In contrast, our method observes moving objects by using a static LRF network in the environment. Experimental results are shown to confirm the effectiveness of the proposed method.

We propose a system that allows multiple groups of users at remote locations to naturally share a 3D image of real objects. All users can interactively observe a 3D stereoscopic image without distortion from their own viewpoints. The system basically consists of a combination of systems: imaging and display. The imaging system captures the real object's images from certain number of viewpoints which are used to generate stereoscopic images from arbitrary viewpoints based on an image-based rendering technique implemented on GPU. The display system interactively generates a 3D virtual image of the real object based on the IllusionHole technique. Users at one place just put the real object on their imaging system to capture a set of its images from sparse viewpoints around it; other groups of multiple users at remote places connected by networks observe its virtual image from arbitrary viewpoints on their display systems.

"MADO Interface" is a tangible user interface consisting of a compact touch-screen display and physical blocks. "MADO" means "window" in Japanese, and MADO Interface is utilized as the real window into the virtual world. Users construct a physical object by simply combining electrical blocks. Then, by connecting MADO Interface to the physical object, they can watch the virtual model corresponding to the physical block configuration (shape, color, etc.) The size and the viewpoint of the virtual model seen by the user depend on the position of MADO Interface, maintaining the consistency between the physical and virtual worlds. In addition, users can interact with the virtual model by touching the display on MADO Interface. These features enable users to explore the virtual world intuitively and powerfully.

We propose a novel interface called Tearable that allows users to continuously experience the real sense of tearing paper. To provide such a real sense, we measured the actual vibration data of tearing a piece of real paper and analyzed them. Based on this data, we utilized hook-and-loop fasteners and a DC motor for representing the sense of tearing. We compared the force given by Tearable with that by a piece of real paper and recommended its reproducibility and usability. In addition, we evaluated Tearable with questionnaires after user experiences.

Abstract We solve the light transport problem by introducing a novel unbiased Monte Carlo algorithm called replica exchange light transport, inspired by the replica exchange Monte Carlo method in the fields of computational physics and statistical information processing. The replica exchange Monte Carlo method is a sampling technique whose operation resembles simulated annealing in optimization algorithms using a set of sampling distributions. We apply it to the solution of light transport integration by extending the probability density function of an integrand of the integration to a set of distributions. That set of distributions is composed of combinations of the path densities of different path generation types: uniform distributions in the integral domain, explicit and implicit paths in light (particle/photon) tracing, indirect paths in bidirectional path tracing, explicit and implicit paths in path tracing, and implicit caustics paths seen through specular surfaces including the delta function in path tracing. The replica‐exchange light transport algorithm generates a sequence of path samples from each distribution and samples the simultaneous distribution of those distributions as a stationary distribution by using the Markov chain Monte Carlo method. Then the algorithm combines the obtained path samples from each distribution using multiple importance sampling. We compare the images generated with our algorithm to those generated with bidirectional path tracing and Metropolis light transport based on the primary sample space. Our proposing algorithm has better convergence property than bidirectional path tracing and the Metropolis light transport, and it is easy to implement by extending the Metropolis light transport.

We present a novel approach for interactive multimedia content creation that establishes an interactive environment in cyberspace in which users interact with autonomous agents generated from video images of real-world creatures. Each agent has autonomy, personality traits, and behaviors that reflect the results of various interactions determined by an emotional model with fuzzy logic. After an agent's behavior is determined, a sequence of video images that best match the determined behavior is retrieved from the database in which a variety of video image sequences of the real creature's behaviors are stored. The retrieved images are successively displayed on the cyberspace to make it responsive. Thus the autonomous agent behaves continuously. In addition, an explicit sketch-based method directly initiate the reactive behavior of the agent without involving the emotional process. This paper describes the algorithm that establishes such an interactive system. First, an image processing algorithm to generate a video database is described. Then the process of behavior generation using emotional models and sketch-based instruction are introduced. Finally, two application examples are demonstrated: video agents with humans and goldfish.

This paper details the design and evaluation of the Delphian Desktop, a mechanism for online spatial prediction of cursor movements in a Windows-Icons-Menus-Pointers (WIMP) environment. Interaction with WIMP-based interfaces often becomes a spatially challenging task when the physical interaction mediators are the common mouse and a high resolution, physically large display screen. These spatial challenges are especially evident in overly crowded Windows desktops. The Delphian Desktop integrates simple yet effective predictive spatial tracking and selection paradigms into ordinary WIMP environments in order to simplify and ease pointing tasks. Predictions are calculated by tracking cursor movements and estimating spatial intentions using a computationally inexpensive online algorithm based on estimating the movement direction and peak velocity. In testing the Delphian Desktop effectively shortened pointing time to faraway icons, and reduced the overall physical distance the mouse (and user hand) had to mechanically traverse.

This paper proposes a virtual chopsticks system using force feedback and object deformation with FEM (finite element model). The force feedback model is established by using a leverage based on the correct chopsticks handling manner, and the force is applied to the index and middle finger. The object deformation is obtained in real-time by calculating inverse stiffness matrix beforehand. We performed experiments to compare the hardness of virtual objects. As a result, we found that a recognition rate of almost 100% can be achieved between virtual objects where the logarithmic difference in hardness is 0.4 or more, while lower recognition rates are obtained when the difference in hardness is smaller than this.

We present a novel method for interactive retrieval of 3D shapes using ysical objects. Our method is based on simple ysical 3D interaction with a set of tangible blocks. As the user connects blocks, the system automatically recognizes the shape of the constructed ysical structure and picks similar 3D shape models from a preset model database, in real time. Our system fully supports interactive retrieval of 3D shape models in an extremely simple fashion, which is completely non-verbal and cross-cultural. These advantages make it an ideal interface for inexperienced users, previously barred from many applications that include 3D shape retrieval tasks.

We propose a method to extract motion individuality from the form of a sport expert and to apply it to figures that have different segment lengths. For this purpose, a standard motion is established by removing the subjective motion from an actor who conducts a sport skillfully, and the surface features (angular velocity and torque of the joint) are extracted for each joint angle difference in each animation frame between the original motion of the sports expert and the standard motion. The surface features and relative timing in the deep structure are transmitted to the characters having different segment lengths by applying them to a standard motion of the characters, which is also made by removing subjective motion in advance.

In this paper, we propose a new technique based on recent neuroimaging studies as a tool for the assessment of interactive systems. For this purpose, we analyze the mental process that takes place while human subjects learn to use new tools by using two different approaches. One is an experiment on task performance based on the conventional direct testing method of a user interface, and the other is an indirect method based on recent neuroimaging studies that indirectly estimate the process of interaction through the observation of the human brain activities. The results obtained from the direct experiment on performance evaluation are compared with those from the indirect analysis of the human brain activity, which is measured by a non-invasive neuroimaging measuring method. The process of acquisition of internal models while subjects learn to use new tools is also discussed.

We propose a real-time interactive system that enables users to generate, manipulate and edit the shape model of a tree based on growth simulation by directly indicating its global and spatial information. For this purpose, three-dimensional (3D) spatial information is introduced to the well-known L-system as an attribute of the growth simulation. Moreover, we propose an efficient data structure of L-strings in order to speed up the process.

This paper describes a method for the consolidated manipulation of virtual and real objects using a "magnetic metaphor". The method reduces the behavioral differences between the virtual and real objects. A limited number of physical laws are selected and simulated for the virtual objects; at the same time, limitations are placed on the physical laws for the real objects. Accordingly, a compromise can be found between the physical laws that operate on virtual objects and those which operate on real objects. Therefore, a system with this method enables a user to manipulate virtual and real objects in a similar manner by expecting the same responses and behaviors according to the same physical laws. Experimental results show that the proposed method improves the task performance in the manipulation of virtual and real objects existing in the same environment simultaneously.

The paper describes a retrieval technique for video databases that is based on gestures. The proposed technique gives users a method to create various video content by intuitive interaction. This database system can extract feature parameters from video, perform automatic indexing, retrieve an appropriate result, and replace a presented object with the retrieval result in real time. Furthermore, we implement the fundamental functions of the proposal database. The retrieval accuracy and computational cost of the system are also described.

An ideal stereoscopic display system for multiple users is proposed. It allows three or more people to simultaneously observe individual stereoscopic image pairs from their own viewpoints. The system tracks the head positions of all of the users and generates distortion-free images for each eye of each user. The system consists of a normal display and a display mask, which has a hole in its center. The display mask is placed over the display surface at a suitable distance from it. By controlling the position of the image drawing area for each user according to the corresponding user's viewpoint, each user can observe the stereoscopic image pairs shown in an individual area of the display system with shutter glasses. On the other hand, no user is able to see the image drawing areas of the other users because these areas are adequately occluded by the display mask. Accordingly, the display system can simultaneously provide intelligible 3D stereoscopic images for three or more moving observers without flicker or distortion.

This paper presents a method of interactively generating natural hand gesture animation using reduced dimensionality from multiple captured data sequences of finger motions conducting specific tasks. This method is achieved by introducing an estimation with multiple regression analysis. Even when the skeletal structure of the user who inputs the motion is different from that of the shape model in the computer, the motion that a user imagines is generated. Experimental results obtained from the interface applied to virtual object manipulation showed that the proposed method generates animation naturally, just as users would expect. This method enables us to make input devices that require minimal user training and computer calibration, and helps to make the user interface intuitive and easy to use.

Methods of interactive image generation using processed video contents, and its 3D model capture are proposed; we mainly stress the key technique of the system and the implementation of moving 3D object extraction. In order to reflect a user's intention for generating new multimedia contents, we discuss the methods of storage, retrieval, and presentation. This system is an example of the novel creation of multimedia contents by using the technologies of computer vision and virtual reality. The user is able to generate novel multimedia contents without shape modeling by a human. The proposed low-cost extraction and interaction algorithm can track objects at 8 frames/sec with sufficient accuracy.

ActiveCube is a bi-directional user interface that supports a person's creative work through constructing and interacting with 3D virtual objects by using actual physical cubes. With this flexible interface, the user can easily construct various 3D structures in a virtual environment by simply combining the cubes. All of the faces of the cubes are the same and can be connected to any face of any other cube. A computer recognizes the constructed 3D structure in real time, so consistency is always maintained between the real environment and its corresponding representation in a virtual environment. Each cube is equipped with a processor for autonomous simulation and communication functions between cubes. A cube also utilizes a sensor for detecting the operational intention of the user and/or a display/actuator used as an output channel. Users can interact with ActiveCube in various ways by using the sensors, and the response to the interaction is also shown by displays/actuators installed on the cube. Each ActiveCube is equipped with both input and output devices, which makes the interface intuitive and helps to clarify the causal relationship between the input of the user's operational intention and the output of simulation results.

This paper describes an interactive manipulation technique for objects extracted from video images by an efficient algorithm in order to produce multimedia contents. An object contained in a video image must be able to be extracted at a reasonable speed and a moving object able to be tracked with sufficient accuracy. Moreover, real object interactions that meet such criteria must be established using techniques for manipulating objects in virtual worlds. The proposed technique has potential to generate novel multimedia contents without using shape modeling. An interactive digital fishtank is described as one example application of the proposed technique. In this application, the user is able to obtain various video sequences of fishtanks from the original video sequence.

A technique is proposed for object manipulation with a virtual tool using multiple exact interactions. Exact test is introduced that uses real-time collision detection for both hand-and-tool and tool-and-object interactions. Chopsticks are adopted for one of the trials of our technique; although they have a very simple shape, they do have multiple functions. Here, a virtual object is manipulated by the virtual chopsticks, which are used by the motion of a user's hand captured by a hand gesture input device. Exact interaction is applied between the hand and chopsticks based on correct table manners. Experimental results demonstrate the effectiveness of the proposed multiple exact interactions, especially for precise object alignment tasks.

Describes an interactive manipulation technique for objects in video images extracted by an efficient algorithm. An object contained in a video image has to be able to be extracted at a reasonable speed and a moving object is able to be tracked within a sufficient accuracy. Moreover, any interaction method for real objects with such functions has to be established using a technique for manipulating objects in virtual worlds. An interactive digital fishtank is described as one example application of the proposed technique. In this application, the user is able to obtain various video sequences of fishtanks from any video sequence.

We propose a manipulation technique to intuitively control the "bird's eye" overview displav of an entire large-scale virtual environment in a display system that present a user with both overviews (global views) and a life-size virtual environment (local view) simultaneously.It enables efficient navigation even in enormous and complicated environments using both global and local views.The motion of the bird's eye viewpoint interlocks with the relative motion of the user's viewpoint and his/her hand, therefore, the user can control the "bird's eve" viewpoint by intuitive manipulation.Sophisticated display techniques are obtained based on the proposed method by introducing some constraints on the parameters of the "bird's eye" viewpoint.Experimental results show a combination of the bird's eye overview image and the life-size local image is displayed to the user by reflecting his/her intuitive manipulation.1

We propose a manipulation environment with virtual and real objects by providing a consolidated manipulation manner for both objects.This approach assists the user and improves the task performance of object manipulation (e.g., speed and accuracy).A limited kinds of physical laws are selected and simulated for virtual objects; at the same time, limitations on the physical laws for real objects are introduced.Accordingly, we reached a compromise between the physical laws that operate on both virtual and real objects.The proposed environment enables a user to manipulate virtual and real objects in the same manner by expecting the same response according to the same physical laws.In the environment, real objects are treated as "substantial" as they are, without using insubstantial images taken by cameras or graphical images generated from geometric shape representations of objects.It is possible to bring a real object into a virtual world on demand, according to the user's irregular and sudden requirements, without using troublesome procedures to reconstruct the object shapes.The configuration of an object manipulation environment using a "magnetic metaphor" is shown as an example.This environment is suitable .forobject manipulation in a combined virtual/real world.

Palmtop displays have been extensively studied, but most of them simply refocus information in the real or virtual world.The palmtop display for dextrous manipulation (PDDM) proposed in this paper allows the users to manipulate a remote object as if they were holding it in their hands.The PDDM system has a small LCD, a 3D mouse and a mechanical linkage (force display).When the user locks onto an object in the center of the palmtop display, s/he can manipulate the object through motion input on the palmtop display with haptic sensation.In this paper, the features of the PDDM with haptic sensation are described, then four operating methods and the haptic representation methods for a trial model are proposed and evaluated.(see Video Figure in the CH196 Video Program)

This paper considers the problem of extracting and tracking complex contours without user interaction. We assume that a complex contour consists of contour segments whose spatial coordinates and intensity gradient vary smoothly in the direction normal to themselves. In our algorithm, digital curves that could correspond to contour segments are extracted by connecting edge pixels using a B-spline based contour segment model. The extracted curves trace the contour segments at the next frame by using the active contour model technique. Experimental results show even occluded contours can be tracked automatically.

We propose a parallel algorithm that efficiently generates an octree from a polyhedral shape representation. The algorithm is simple and can apply to general (non-convex) objects. The parallelized algorithm is based on two ideas for the assignment of multiple processors. The algorithm is implemented and tested on MIMD multi-processors having a shared memory. Experimental results, which demonstrate the effectiveness and efficiency of the proposed method are given (e.g. 2.5 seconds are required to generate an octree shape representation from a polyhedral object having 148 polygons). Through investigation of the performance of the proposed parallel algorithm, the features of the parallelism are discussed.

A new method to detect deformations of facial parts from a face image regardless of changes in the position and orientation of a face using the genetic algorithm is proposed. Facial expression parameters that are used to deform and position a 3D face model are assigned to the genes of an individual in a population. The face model is deformed and positioned according to the gene values of each individual and is observed by a virtual camera, and a face image is synthesized. The fitness which evaluates to what extent the real and synthesized face images are similar to each other is calculated. After this process is repeated for sufficient generations, the parameter estimation is obtained from the genes of the individual with the best fitness. Experimental results demonstrate the effectiveness of the method.

We describe a method to detect hand position, posture and finger bendings using multiple camera images. Stable detection can be achieved by using skeleton images, and this is confirmed through experiments. This system can be used as a user interface device in a virtual environment, replacing glove-type devices and overcoming most of the disadvantages of contact-type devices. Future work includes verification of the method's availability as a gesture-based man-machine interface system.

We propose a real-time algorithm for path planning in a dynamically changing 3-D environment where the motion of the obstacles cannot be predicted. The method represents everything in the environment (an arbitrarily shaped robot and static/dynamic obstacles) with an octree that makes no distinction of the movability of objects. A collision free path for a robot with arbitrary motion (translation and rotation) in a dynamic 3-D environment is efficiently sought by using the real-time A* algorithm and the potential field generated from each black cell of the octree. Parallel computation is used to speed up the generation of the potential field. Finally, the experimental results demonstrate the efficiency of the proposed path planning method for a dynamically-changing 3-D environment with arbitrary motion.

A method is proposed to help a user manipulate an object in a virtual environment. The method does not give special properties to the object in advance, and does not use special hardware. Instead, it uses only visual constraints among object features that are dynamically selected while the user manipulates the object. It uses face-to-face, edge-to-face, and vertex-to-face constraints; therefore, it provides a natural and intuitive environment for virtual object manipulation that replicates the task in a real environment. The constraint is transferred with a smooth motion. Experimental results show the effectiveness of this method in providing the user with a natural impression of motion in a virtual environment equipped with 3-D/6-D input devices and a conventional graphic workstation to finish all procedures within the cycle time of the human perceptual processor for objects with complicated shapes.

Proposes an efficient and simple method for finding a collision-free path and orientation for a rigid robot in a dynamic observable 3-D environment for unmanned aerial vehicles (UAVs). The method uses an octree for representing every object (robot and static/dynamic obstacles) in the environment without any distinction of the movability of objects; therefore, all objects are dealt with in the same way. The path of a robot from its starting position to the given goal with arbitrary motion (i.e., translation and rotation) in a 3-D environment is efficiently searched for in successive adjoining regions (octree white cells) by using the potential field generated from each black cell of the octree. The algorithm is simple, so it can easily be accelerated by using parallelization techniques. Experimental results obtained under several conditions, such as a point shaped robot and arbitrarily shaped robots in static/dynamic environments, are reported.

Since their advent, interaction with computers has been a very fascinating field of research. Though, we have come a long way from turning knobs and punching cards to using keyboards and pointing devices, natural language interaction has not seen widespread use as a general means of interaction. The thesis of this paper is that some application fields, specially those dealing with computer graphics, can benefit from the interaction of natural language and hand gestures. This bimodal means of interaction in computer-graphics-based task, complements the deficiencies of just applying either one of the two modes. This paper, describes current research efforts taking place at ATR for combining hand gestures and verbal descriptions for generating, modifying and manipulating 3D computer graphics objects.

We propose a new method for acquiring time-sequential range images that provide dense range data. In our approach, stereo pairs of thermal and intensity images are synchronously acquired and are mutually registered. The thermal images are segmented into isotemperature regions. Contour-based matching is done for the isotemperature regions in the thermal images independently at each time instant, and by temporal correspondence, possible matching pairs of contours are generated. By evaluating the similarities of the pairs, consistent and likely pairs are chosen. To get dense range data, intensity profiles within the isotemperature regions are matched by dynamic programming. Experiments on real scenes, including a sequence showing a moving human being, show promising results.>

We propose an efficient method for detecting potential collisions among multiple objects with arbitrary motion (translation and rotation) in 3D space. The method is useful for online monitoring and path planning in a 3D environment in which there are multiple independently-moving objects. The method consists of two main stages: 1) the coarse stage, an approximate test is performed to identify interfering objects in the entire workspace using octree representation of object shapes; and 2) the fine stage, polyhedral representation of object shapes is used to more accurately identify any object parts that might cause interference and collisions. For this purpose, specific pairs of faces belonging to any of the interfering objects found in the first stage are tested, thus performing detailed computation on a reduced amount of data. Experimental results, which demonstrate the efficiency of the proposed collision detection method, are given.

A new method for estimating human postures at a time instant from multiple images using a genetic algorithm is proposed. The posture parameters to be estimated are assigned to the genes of individuals in the population. For each individual, its fitness evaluates to what extent the multiple human images synthesized by deforming a 3D human model according to the values of the genes are registered to the real multiple human images. Genetic operations such as natural selection, crossover and mutation are performed, and individuals in the next generation are generated. After a certain number of repetitions for these processes, the estimated parameter values are obtained from the individual with the best fitness. Experiments using synthesized human multiple images show promising results.

A new method for acquiring time-sequential range images is proposed. Stereo pairs of thermal and intensity images are synchronously acquired and are mutually registered. Stereo thermal images are segmented into isotemperature regions. Contour based matching is done for the isotemperature regions. To supplement sparse range data obtained from the contour matching, dynamic programming matching is performed for either intensity profiles or edges in the stereo intensity images. By corresponding pixel pairs obtained from the matching processes, the 3-D coordinates of the points can be calculated. Experiments with real scenes having moving human beings show promising results.>

The authors seek to reconstruct a polyhedral representation of surfaces from range data that can adapt to the intrinsic surface shape and that might be used as an accurate CAD model. An adaptive mesh model for hierarchical triangulation of 3-D objects is presented. An adaptive mesh generation algorithm is developed that recursively bisects mesh elements by increasing the number of mesh nodes according to surface curvatures. The recursive subdivision based on such a viewpoint-invariant feature yields the hierarchical surface triangulation that is intrinsic to the surface, and satisfies the absolute accuracy criterion. In order to avoid cracks that often occur during adaptive subdivision, an algorithm is developed that collects subdivision information by recursively expanding the region of reference until a sudden surface change is observed. Computation results on real range data of human faces are shown.>

A homotopy describes the transformation of one arbitrary curve into another that shares the same endpoints. In this paper, we propose a deformable cylinder model, based on homotopy, in which an arbitrary surface interpolated between two contours via a blending function is transformed into another surface over time. We then show how this homotopic deformation can be applied to the realistic animation of human faces in a virtual space teleconferencing system. Specifically, we show that facial expressions such as wrinkling of the forehead and opening and closing of the mouth can be synthesized and animated in real time through 3D homotopic deformations.

A virtual environment, which is created by computer graphics and an appropriate user interface, can be used in many application fields, such as teleopetution, telecommunication and real time simulation.Furthermore, if this environment could be shared by multiple users, there would be more potential applications.Discussed in this paper is a case study of building a prototype of a cooperative work environment using a virtual environment, where more than two people can solve problemscooperatively, including design strategies and implementirig issues.An environment where two operators can directly grasp, move or release stereoscopic computer graphics images by hand is implemented.The system is built by combining head position tracking stereoscopic displays, hand gesture input devices and graphics workstations.Our design goal is to utilize this type of interface for a future teleconferencing system.In order to provide good interactivity for users, we discuss potential bottlenecks and their solutions.The system allows two users to share a virtual environment and to organize 3-D objects cooperatively.

The authors attempt to combine results from different vision cues such as contour, motion and shading in an image sequence to obtain as complete a 3-D model as possible. Two problems must be solved. First, different features may appear to be the same image data. They should be classified so that different methods can be applied precisely. Second, output from different approaches may supplement, or overlap, each other. They should be qualified and then combined correctly and effectively. These issues are addressed by analyzing an image sequence taken when objects rotate around an axis. The features are verified according to their behaviour in the continuous images. Unknown areas and areas with single or multiple measurements are located. A strategy for combining these data is given.>

Surface reconstruction and visualization from sparse and incomplete surface data is a fundamental problem and has received growing attention in both computer vision and graphics. The paper introduces a novel approach to recovering and visualizing complex shapes from range data, in which a surface of unknown shape is reconstructed with view-invariant characteristics on arbitrary viewplanes from sparsely sampled surface range data so that the entire surface can be visualized from any view points with constant. The authors develop a graphical reconstruction model based on differential geometry using adaptive and arbitrarily oriented meshes, in which the number of surface nodes is generated dynamically on an active viewing plane and then increased in number and influence one another until the entire surface has been interpolated with a sufficient accuracy. The computation results on real range data of human faces are shown.>

This paper explores a shape-from-contour method for acquiring a 3D model by using a continuous sequence of images taken as an object rotates. The authors analyze the areas that are unexposed to contours and detect them for further investigation. They describe a general approach to use the shape from contours. The goal is to establish a 3D model of the human face for the growing needs of visual communications. Some good results have been obtained.>

A method for object manipulation using an active camera is introduced. By actively moving the camera to proper positions with desired viewing angle from objects of interest, it is possible to acquire data to realize the robust visual feedback control of a robot. This approach avoids complicated 3-D modeling, and the image processing carried out is driven by tasks. Active camera control for robot guidance and image understanding is addressed.>

A computational scheme is presented for obtaining a characteristic description of a free-form curved surface from 3-D range images whose natural modes are in the form of level (equidistance) contours. The novelty in this scheme is that dense surface contours are used to directly estimate the surface curvatures in a systematic fashion without having to explicitly or implicitly compute any partial derivatives. The principle of the scheme is described, and the framework of computational paradigm is outlined for a shape description (shape from level contours) of the free-form curved object from its local surface properties. The objective is to obtain an invariant viewpoint and stable representation that is useful in 3-D object reconstruction and recognition. Although the scheme is based on analysis of level contours, the computation model for shape representation is general and applicable to any dense range image.>

We have studied a stereo-based approach to three-dimensional face modeling and facial image reconstruction virtually viewed from different angles. This paper describes the system, especially image analysis and facial shape feature extraction techniques using information about color and position of face and face components, and image histogram and line segment analysis. Using these techniques, the system can get the facial features precisely, automatically and independent of facial image size and face tilting. In our system, input images viewed from the front and side of the face are processed as follows: the input images axe first transformed into a set of color pictures with significant features. Regions are segmented by thresholding or slicing after analyzing the histograms of the pictures. Using knowledge about color and positions of the face, face and hair regions are obtained and facial boundaries extracted. Feature points along the obtained profile are extracted using information about curvature amplitude and sign, and knowledge about distance between the feature points. In the facial areas which include facial components, regions are again segmented by the same techniques with color information from each face component. The component regions are recognized using knowledge of facial component position. In each region, the pictures are filtered with various differential operators, which are selected according to each picture and region. Thinned images are obtained from the filtered images by various image processing and line segment analysis techniques. Then, feature points of the front and side views are extracted. Finally, the size and position differences and facial tilting between two input images are compensated for by matching the common feature points in the two views. Thus, the three-dimensional data of the feature points and the boundaries of the face are acquired. The two base face models, representing a typical Japanese man and woman, are prepared and the model of the same sex is modified with 3D data from the extracted feature points and boundaries in a linear manner. The images, which are virtually viewed from different angles, are reconstructed by mapping facial texture to the modified model.

Statistical characteristics of video signals for video packet coding, are clarified and a variable-bit-rate coding method for asynchronous transfer mode (ATM) networks is described that is capable of compensating for packet loss. ATM capabilities are shown to be greatly affected by delay, delay jitter, and packet loss probability. Packet loss has the greatest influence on picture quality. Packets may be lost either due to random bit error in a cell header or to network control when traffic is congested. A layered coding technique using discrete-cosine transform (DCT) coding is presented which is suitable for packet loss compensation. The influence of packet loss on picture quality is discussed, and decoded pictures with packet loss are shown. The proposed algorithm was verified by computer simulations.>