Computer Animation and Virtual Worlds

Cover image for Vol. 28 Issue 1

Early View (Online Version of Record published before inclusion in an issue)

Edited By: Nadia Magnenat Thalmann and Daniel Thalmann

Impact Factor: 0.548

ISI Journal Citation Reports © Ranking: 2015: 88/106 (Computer Science Software Engineering)

Online ISSN: 1546-427X

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  1. 1 - 22
  1. RESEARCH ARTICLES

    1. Interactive authoring of bending and twisting motions of short plants using hand gestures

      Kan Chen and Henry Johan

      Version of Record online: 9 FEB 2017 | DOI: 10.1002/cav.1747

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      In this paper, we propose an approach to interactively author the bending and twisting motions of short plants using hand gestures, especially suitable for grass, flowers, and leaves. Our method is based on the observations that hand motions can represent the bending and twisting motions of short plants and using a hand to describe motions is natural and proficient for human. We therefore use a hand as a “puppet” to author the animation of one single short plant based on transferring the motions of a hand to the motions of a short plant. We first author the global motions of the short plant followed by the motions of its elements such as leaves and flowers. We also propose a framework to utilize the animation results to animate a field of short plants and further adjust the motion effects according to the properties of the short plants, such as rigidity. As a result, users can intuitively and rapidly author and generate their desired motions of short plants under the influence of external forces. Especially, our method is accessible to non-expert users and suitable for fast prototyping and authoring specific motions of short plants such as in cartoons.

  2. SPECIAL ISSUE PAPERS

    1. Perceptual evaluation of synthetic gaze jitter

      Krzysztof Krejtz, Andrew Duchowski, Heng Zhou, Sophie Jörg and Anna Niedzielska

      Version of Record online: 2 FEB 2017 | DOI: 10.1002/cav.1745

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      We present a procedural model to synthesize the subtleties of eye motions. Our model adds microsaccadic jitter and pupil unrest, both modeled by pink noise, to the standard main sequence. Perceptual experiments show that when the motion is data-driven or parameterized pink noise, some jitter, but not too much, is perceived as more natural than when it is excessive or absent.

    2. Robust standing control with posture optimization

      Zumra Kavafoglu, Ersan Kavafoglu and Arjan Egges

      Version of Record online: 24 JAN 2017 | DOI: 10.1002/cav.1746

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      We present a physics-based approach for robust center of mass shifting during standing. Desired standing posture is defined by a number of high-level features and an online optimization process calculates the kinematic postures for the lower body and the pelvis. A physics-based arm control strategy is devised for increasing the robustness of the character. The proposed approach results in robust standing motions with automatic knee-bending behavior as the character shifts its center of mass in all dimensions.

  3. RESEARCH ARTICLES

    1. Novel fluid detail enhancement based on multi-layer depth regression analysis and FLIP fluid simulation

      Yuxing Qiu, Lipeng Yang, Shuai Li, Qing Xia, Hong Qin and Aimin Hao

      Version of Record online: 13 DEC 2016 | DOI: 10.1002/cav.1741

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      In this paper, a novel integrated method for effective modeling and realistic enhancement of scale-sensitive fluid simulation details is proposed. The core of the method is the organic of multi-layer depth image regression analysis and fluid implicit particle fluid simulation, of which the regression analysis induces the criterion where the fluid details should be produced.

    2. A synergy-based control solution for overactuated characters: Application to throwing

      Ana Lucia Cruz Ruiz, Charles Pontonnier, Jonathan Levy and Georges Dumont

      Version of Record online: 24 NOV 2016 | DOI: 10.1002/cav.1743

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      We present a low-dimensional solution for the control of overactuated models in animation, such as musculoskeletal models. Our framework extracts synergies from human subjects and adapts them through a series of optimizations.We apply the framework on throwing motions, and the results show that these motions can be accurately reproduced on a character with a simplified muscular structure, while preserving important characteristics in the original synergies or control signals.

    3. Populating virtual cities using social media

      Abdullah Bulbul and Rozenn Dahyot

      Version of Record online: 24 NOV 2016 | DOI: 10.1002/cav.1742

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      This paper presents a method for automatically populating geo-located virtual cities using the information gathered from social media. We place and orient static agents in a city considering where people look at, which is extracted from the shared visual content in social networks. Additionally, dynamic agents are distributed along the city to reflect the volume of temporal and spatial distribution of social media activity.

  4. SPECIAL ISSUE PAPERS

    1. The effect of animation controller and avatar on player perceptions

      Aline Normoyle and Sophie Jörg

      Version of Record online: 20 NOV 2016 | DOI: 10.1002/cav.1731

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      Designing controllers for digital games requires making trade-offs between the naturalness of the character's motions and the promptness of the character's response. In a study comparing different controllers, we find that players are most satisfied with their own performance using our controller with the least natural motions, that differences in animation can alter players' enjoyment, that players do not necessarily report increased motion quality in a game even when they do outside of the game, and that the appearance of the avatar model affected the perception of the character.

    2. Real-virtual fusion model for traffic animation

      Xin Yang, Wanchao Su, Jian Deng, Xiaogang Jin, Guozhen Tan and Zhigeng Pan

      Version of Record online: 12 OCT 2016 | DOI: 10.1002/cav.1740

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      We present an animated traffic simulation method to enhance the sense of reality and diversity of traffic flows. Our method includes continuous data input providing an interactive control function. Using our method, we can generate traffic animations with inverse and irregular vehicle driving behaviors.

  5. Research Articles

    1. Computational mental simulation: A review

      Mihai Polceanu and Cédric Buche

      Version of Record online: 12 OCT 2016 | DOI: 10.1002/cav.1732

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      Mental simulation is a central capability of the human mind. Computational approaches are limited to particular uses, but pave the way towards a generic anticipation framework for virtual and robotic agents. The authors discuss current issues, draw insights and propose a way to unify seemingly separate capabilities into a single agent architecture.

    2. A parsimonious model for locomotor in virtual agents based on dynamical coupling with the environment

      Angel Zaldivar Pino, Manuel Gonzalez Bedia and Francisco José Seron Arbeloa

      Version of Record online: 4 OCT 2016 | DOI: 10.1002/cav.1733

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      In this paper, the main proposition assumes that the agent does not need a full model or to make inferences before taking actions; rather, the information necessary for any action can be derived from the environment with simple computations and very little internal state. The agents are endowed with a sensing device, an oscillator network as controller and actuators to interact with the environment. The parameter values are defined in an evolutionary process depending on the task to be performed.

    3. Perception of collisions between virtual characters

      Sybren A. Stüvel, A. Frank van der Stappen and Arjan Egges

      Version of Record online: 20 SEP 2016 | DOI: 10.1002/cav.1728

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      This paper investigates the accuracy of human observers in recognizing collisions between virtual characters. We show the result of two user studies, where participants classify scenarios as “colliding” or “not colliding.” On average respondents correctly classified 72% (static) and 68% (animated) of the scenarios. The maximum uncertainty was observed when the characters are overlapping slightly and that there is a significant bias towards answering “not colliding.” We also discuss differences in bias in the recognition of upper-and lower-body collisions.

  6. Special Issue Papers

    1. Generating hand motion from body motion based on hand pose estimation

      Masaki Oshita and Yuta Senju

      Version of Record online: 6 SEP 2016 | DOI: 10.1002/cav.1730

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      We propose a method to generate hand motion from full-body motion. We train a support vector machine from a number of full-body motions with manually specified hand-pose keyframes in order to choose one of four key hand poses based on the full-body pose. We realize smooth transitions between key hand poses and add small movements of fingers for generating plausible hand motions.

  7. RESEARCH ARTICLES

    1. Exploitation of multiplayer interaction and development of virtual puppetry storytelling using gesture control and stereoscopic devices

      Hui Liang, Jian Chang, Shujie Deng, Can Chen, Ruofeng Tong and Jian Jun Zhang

      Version of Record online: 16 AUG 2016 | DOI: 10.1002/cav.1727

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      Digital storytelling is a powerful pedagogical tool for young children. In this paper, we 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. Experiments show great potential to stimulate young children's learning abilities through collaboration tasks.

  8. Research Articles

    1. Interaction with virtual crowd in Immersive and semi-Immersive Virtual Reality systems

      Marios Kyriakou, Xueni Pan and Yiorgos Chrysanthou

      Version of Record online: 15 AUG 2016 | DOI: 10.1002/cav.1729

  9. Special Issue Papers

    1. Anticipatory balance control and dimension reduction

      Amir H. Rabbani, Michiel van de Panne and Paul G. Kry

      Version of Record online: 13 JUL 2016 | DOI: 10.1002/cav.1726

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      Learned center-of-mass reference trajectories enable anticipatory control for a variety of tasks, including (from left to right top to bottom): fast changes of pose; punching; catching and lifting; pushing; hitting and pulling.

  10. Research Articles

    1. Simulation and visualization of adapting venation patterns

      Monssef Alsweis, Oliver Deussenn and Jia Liu

      Version of Record online: 24 JUN 2016 | DOI: 10.1002/cav.1723

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      Illustration of visually realistic development system for different leaves type is described by a growth function relative elementary growth rate that reacts to hormone (Auxin) sources embedded in the leaf blade.

    2. Image-based embroidery modeling and rendering

      Dele Cui, Yun Sheng and Guixu Zhang

      Version of Record online: 8 JUN 2016 | DOI: 10.1002/cav.1725

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      This paper presents an image-based embroidery rendering method, which combines stroke-based rendering techniques with the Phong lighting model to generate picturesque images with embroidery style. We build a 3D stitch model and derive some most commonly used stitch patterns from it. Then we segment the input image into regions, calculate region-wise parameters to apply single or multiple layers of stitches onto the specific regions and render them under a virtual light source to create the effects of lighting and shading.

    3. Essential techniques for laparoscopic surgery simulation

      Kun Qian, Junxuan Bai, Xiaosong Yang, Junjun Pan and Jianjun Zhang

      Version of Record online: 2 JUN 2016 | DOI: 10.1002/cav.1724

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      In this paper, we proposed 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.

    4. Determining personality traits of racing game players using the open racing car simulator: toward believable virtual drivers

      Andre Possani-Espinosa, J. Octavio Gutierrez-Garcia and Isaac Vargas Gordillo

      Version of Record online: 26 MAY 2016 | DOI: 10.1002/cav.1722

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      A decision tree methodology for profiling players based on their goal-oriented driving behaviors is proposed. 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.

    5. Realistic modeling of porous materials

      Rodrigo Baravalle, Leonardo Scandolo, Claudio Delrieux, Cristian García Bauza and Elmar Eisemann

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1719

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      *We designed a new algorithm for porous geometry generation using dynamical systems and particle systems.*The generated bubbles automatically follow any provided object shape.*It is possible to obtain several materials varying intuitive parameters (bubble's randomness, separation, etc,).

    6. Incorporating particle motion into an ADF for fast coupling of fluids with rigid and deformable solids

      Jong-Hyun Kim, Chang-Hun Kim and Jung Lee

      Version of Record online: 18 APR 2016 | DOI: 10.1002/cav.1689

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      We 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. In some previous methods, the motion of every water particle is checked when simulating the collision with the solid in the coupling process, and the computational cost becomes very great as the number of particles increases. If only the particles on the leaf nodes surrounding the solid are considered, this reduces the computational cost of collision detection, but some collisions may not be detected. This may lead to the “tunneling” artifact, in which particles with high velocities skip across the layer of leaf nodes.

  11. Special Issue Papers

    1. Multi-group motion planning in virtual environments

      Erion Plaku, Sara Rashidian and Stefan Edelkamp

      Version of Record online: 9 FEB 2016 | DOI: 10.1002/cav.1688

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      Towards enhancing automation, this paper proposes an approach for multi-group motion planning, where the objective is to compute a collision-free and dynamically feasible trajectory that reaches at least one goal from each group. The approach is based on a hybrid search which uses generalized traveling salesman tours over a roadmap to guide the sampling-based expansion of a motion tree. The approach works in conjunction with physics-based game engines to provide an increased level of realism.

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