The dynamic effects of smoke are impressive in illustration design, but it is a troublesome and challenging issue for inexpert users to design smoke effects without domain knowledge of fluid simulations. In this work, we propose DualSmoke, a two-stage global-to-local generation framework for interactive smoke illustration design. In the global stage, the proposed approach utilizes fluid patterns to generate Lagrangian coherent structures from the user’s hand-drawn sketches. In the local stage, detailed flow patterns are obtained from the generated coherent structure. Finally, we apply a guiding force field to the smoke simulator to produce the desired smoke illustration. To construct the training dataset, DualSmoke generates flow patterns using finite-time Lyapunov exponents of the velocity fields. The synthetic sketch data are generated from the flow patterns by skeleton extraction. Our user study verifies that the proposed design interface can provide various smoke illustration designs with good user usability. Our code is available at https://githubcom/shasph/DualSmoke.

In this study, we propose an efficient city-generation method based on user sketches that combine a deep generative model with the procedural modeling approach. The proposed framework adopts the deep learning-based network of conditional generative adversarial networks. For the data training, we randomly generated three-dimensional cities from perlin noise. The contours of the cities were extracted by the holistically-nested edge detection approach. The proposed method is a deep learning model that uses paired data of cities generated by a procedural model, along with the corresponding hand-drawn style sketches.

Bi-manual interaction in virtual reality (VR) is generally used and has unlimited potential in interdisciplinary fields such as health care, education, and industry due to the facts of its conveniences, intuition, and beyond. With the continuous development of these interfaces, passive monitoring of user state can play a key role in extending the immersive VR manual experience and tracking activities for user well-being. To date, research on investigation immersive and intuitive manual experience has mostly conducted in questionnaire. It may have several disadvantages such as differences in understanding and interpretation or hard to convey feelings and emotions. However,when using VR devices, physiological signals, such as electroencephalograms (EEG), are recorded, the interaction of the user in the virtual environment can be adjusted in real time according to the cognitive state of the user. The current VR headset provides a logical, convenient, and non-obtrusive framework for mounting EEG sensors. The study evaluates the feasibility of passively monitoring cognitive work loads via EEG during classical gesture tasks in the interactive VR environment. Data were collected from 15 participants and the EEG features were analyzed with respect to task performance. The results indicate that participants feel more intuitive and relaxed when using Vive wands in the virtual environment but the Leapmotion has the great potential for providing immersive experience.

Drawing the facial features of anime characters at different ages is challenging in the creation process. Since characters’ facial features at different ages have obvious differences, it is difficult, especially for novices to accurately illustrate the age features of anime characters. Conventional data-driven drawing interfaces for anime characters focus on the visual features of hair, emotion, and coloring but fail to provide age-specific drawing guidance. To address this gap, we propose AgeFace, an interactive drawing interface that assists users in creating facial features with age-specific features based on user input strokes. We evaluated the usability of AgeFace by a user experience experiment and a comparison experiment with baseline approaches. The results verified that AgeFace could achieve better performance in usability and better support in the creative process than baseline systems.

This research focuses on interpreting the Eshelby twist behavior into kinetic façade design, which is a continuous crystallographic twist generated by the torsional force of an axial screw dislocation in a one-dimensional nanowire structure. The mechanism can be adjusted to the kinetic façade, changing dynamically rather than being static or fixed and allowing movement to occur on a building's surface with the potential to reduce sunlight exposure. Natural light is essential for making human work in building spaces more productive. The solution to the issue of inappropriate natural light in indoor spaces is a kinetic façade, which is self-adjustable according to sunlight intensity. The simulation results before and after installing the façade show the sunlight exposure value were 2030 kWh/m2and 300 kWh/m2per year, respectively. 2030 kWh/m2, this value is too excessive for direct sunlight for users living in the space. As a result, the sunlight exposure value after installation is acceptable for users; it is verified that the proposed design can strongly decrease sunlight exposure. These findings indicate that the Eshelby twist is the principal phenomenon facilitating façade movement.

Special skills are required in portrait painting, such as imagining geometric structures and facial detail for final portrait designs. This makes it a difficult task for users, especially novices without prior artistic training, to draw freehand portraits with high-quality details. In this paper, we propose dualFace, a portrait drawing interface to assist users with different levels of drawing skills to complete recognizable and authentic face sketches. Inspired by traditional artist workflows for portrait drawing, dualFace gives two-stages of drawing assistance to provide global and local visual guidance. The former helps users draw contour lines for portraits (i.e., geometric structure), and the latter helps users draw details of facial parts, which conform to the user-drawn contour lines. In the global guidance stage, the user draws several contour lines, and dualFace then searches for several relevant images from an internal database and displays the suggested face contour lines on the background of the canvas. In the local guidance stage, we synthesize detailed portrait images with a deep generative model from user-drawn contour lines, and then use the synthesized results as detailed drawing guidance. We conducted a user study to verify the effectiveness of dualFace, which confirms that dualFace significantly helps users to produce a detailed portrait sketch.

In this paper, we propose a user interface that enables users to intuitively retrieve relevant motions from a database and edit them by drawing motion trajectories on the screen. This system consists of two-stage operations to provide global-level and local-level motion editing: a global stage that enables users to design the body movement in virtual space roughly, and a local stage that enables users to design detailed movements such as limbs movement. We verified the proposed system with character animation editing with both global and local stages.

Visual cryptography (VC) is an encryption technique for hiding a secret image in distributed and shared images (referred to as shares). VC schemes are employed to encrypt multiple images as meaningless, noisy patterns or meaningful images. However, decrypting multiple secret images using a unique share is difficult with traditional VC. We propose an approach to hide multiple images in meaningful shares. We can decrypt multiple images simultaneously using a common share, which we refer to as a magic sheet . The magic sheet decrypts multiple secret images depending on a given share. The shares are printed on transparencies, and decryption is performed by physically superimposing the transparencies. We evaluate the proposed method using binary, grayscale, and color images.

In this article, we introduce an efficient and versatile numerical aerodynamics model for general three-dimensional geometry shapes in potential flow. The proposed model has low computational cost and achieves an accuracy of moderate fidelity for the aerodynamic loads for a given glider shape. In the geometry preprocessing steps of our model, lifting-wing surfaces are recognized, and wake panels are generated automatically along the trailing edges. The proposed aerodynamics model improves the potential theory-based panel method. Furthermore, a new quadratic expression for aerodynamic forces and moments is proposed. It consists of geometry-dependent aerodynamic coefficient matrices and has a continuous representation for the drag/lift-force coefficients. Our model enables natural and real-time aerodynamics simulations combined with general rigid-body simulators for interactive animation. We also present a design system for original gliders. It uses an assembly-based modeling interface and achieves interactive feedback by leveraging the partwise precomputation enabled by our method. We illustrate that one can easily design various flyable gliders using our system.

Abstract A model to rate color combinations that considers human aesthetic preferences is proposed. The proposed method does not assume that a color palette has a specific number of colors, i.e., input is not restricted to a two‐, three‐, or five‐color palettes. We extract features from a color palette whose size does not depend on the number of colors in the palette. The proposed rating prediction model is trained using a human color preference dataset. The model allows a user to extend a color palette, e.g., from three colors to five or seven colors, while retaining color harmony. In addition, we present a color search scheme for a given palette and a customized version of the proposed model for a specific color tone. We demonstrate that the proposed model can also be applied to various palette‐based applications.

This paper proposes a pattern-guided framework for immersed rigid body simulations involving unsteady dynamics of a fully immersed or submerged rigid body in a still flow. Instead of the heavy computation of fluid-body coupling simulations, a novel framework considering different flow effects from the surrounding flow is constructed by parameter estimation of force coefficients. We distinguish the flow effects of the inertial, viscous and turbulent effects to the rigid body. It is difficult to clarify the force coefficients of viscous effect in real flow. In this paper we define the control parameters of viscous forces in rigid body simulator, and propose a energy optimization strategy for determining the time series of control parameters. This strategy is built upon a motion graph of motion patterns and the turbulent kinetic energy. The proposed approach achieves efficient and realistic immersed rigid body simulation results, and these results are relevant to the real-time animations of body-vorticity coupling.

Abstract This paper presents a procedure for modelling aggregates such as piles that consist of arbitrary components. The method generates an aggregate of components that need to be accumulated, and an aggregate shape represents the surface of the target aggregate. The number of components and their positions and orientations are controlled by five parameters. The components, the aggregate shape and the parameters are the inputs for the method which involves placement and refinement steps. In the placement step, the orientation and initial position of a component are determined by a non‐periodic placement such that each component overlaps its neighbours. In the refinement step, to construct a pile structure, the position of each component is adjusted by reducing the overlap.

This paper presents an effective feature descriptor that integrates intensity order and textures in multi support regions into a compact vector. We first propose the novel Intensity Order Local Binary Pattern (IO-LBP) to encode the texture around each point in an interest region, divide the region according to pixel intensity orders, and then pool patterns to these segments. The IO-LBP descriptor is built by concatenating histograms of all segments together. Besides, multi support regions are used to further improve the discriminative ability. The proposed descriptor can effectively capture both local and global information of an interest region and thus high performance is expected. We evaluate IO-LBP on the standard Oxford dataset and additional images of shadows. Experimental results show that our method is not only invariant to common photometric and geometric transformations, such as illumination change, image rotation, but also robust to complex illumination effects caused by shadows. A significant improvement in performance, comparing to state-of-the-art descriptors, is achieved by IO-LBP.

We present in this paper a framework that generates free fall motions for the object within a still fluid. We introduce a new motion synthesis approach where six characteristic motion prototypes of free fall are defined and synthesized, and then the motion trajectory is specified form free fall motion graph. We automatically create motion sequences using trajectory search tree and pre-computed trajectory database. The proposed approach can produce realistic and controllable free fall motion that could be applied in many different applications, including virtual reality, game and other entertainment productions.

In computer graphics, with improvement in hardware performance, more detailed production of three-dimensional (3D) models is required. However, the modeling process becomes tedious if it is carried out manually, in particular for natural objects because of their complexities. Therefore, it is important to generate content procedurally or automatically in order to efficiently produce such models. Furthermore, a purely procedural approach prevents the user from exercising total control over the outcome. The solution we proposed here is to combine the power of procedural modeling with the flexibility of manual editing. In this paper, we focus on the generation of pebble mosaics to achieve the distribution of numerous pebbles while maintaining distribution controllability. Existing research on rock modeling and digital mosaics has not focused on user-specified arrangements, whereas in this work, we present an interactive method for generating pebble mosaics. This is achieved through designing an underlying tensor field that specifies the pattern of pebble arrangement. The experimental results show that a realistic visual quality is obtained using our proposed method.

In this study, a method for modeling trees with rugged surfaces by simulating tree growth is proposed. The phenomena of cell division is considered for simulating tree growth. There are two types of cells that affect the growth of trees, namely, the apical meristem cells and the cambium cells. The former cells lie at the apex of a branch and are responsible for the extension of the branch. The latter cells cover the surface of the tree and are responsible for its lateral growth. Further, knots are generated by unusual and uneven growth of the cambium cells. To simulate these phenomena, a tree is modeled as a polygon mesh which grows by displacing the vertices of the mesh. Each vertex acts as an apical meristem cell or a cambium cell. The tree growth is defined by an L-System. Subsequently, tree models with rugged surfaces, such as those including knots, are generated.

We are studying non-photo realistic rendering (NPR) with the goal of developing an image expression tool to create artworks by the NPR technique. The purpose of most NPR researches is to simulate typical painting styles, so they focus on techniques to create brushstrokes. These superficially modified images cannot deviate far from the source photo. If a rendered image is seen from a distance, it is difficult to tell the difference from the source photo. This fact makes us realize that other important elements to add artistic expression to the photographs exist. We supposed that the distribution of bright and dark parts over the painting is essential and proposed the effective way to modify that. Our novel technique is based on knowledge about human optical illusions and basic visual design rules. We integrate this technique into our NPR system, which was used to make the artworks selected by SIGGRAPH 2002 2D art gallery. Furthermore, we present new features that allow artist to select appropriate area for extreme expressions, to create many types of brushstrokes, and to choose more than two types of brushstrokes for a single artwork.

Recently, several kinds of mapping technology, such as texture mapping and bump mapping, have played a very important role in the realization of more realistic image synthesis. The textures to be mapped are often obtained by using an optical scanner or a video camera. However, it is not easy to obtain a suitable image by taking a photo. We consider it very important to be able to generate a variety of textures and patterns easily according to the requirements. This paper proposes a new method of generating stone wall patterns as a specific case of a generalized texture generator. The advantage of the method is that it allows the user to generate a variety of stone wall patterns by specifying a few simple parameters. We have applied it to a visual simulation system in order to represent such stone textures as walls, pavements, and steps. This paper also gives some examples of its applications.