Computer Animation and Virtual Worlds

Cover image for Vol. 25 Issue 5-6

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

Edited By: Nadia Magnenat Thalmann and Daniel Thalmann

Impact Factor: 0.422

ISI Journal Citation Reports © Ranking: 2013: 97/105 (Computer Science Software Engineering)

Online ISSN: 1546-427X

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  1. 1 - 24
  1. Research Articles

    1. Vortex particle smoke simulation with an octree data structure

      Zhanpeng Huang, Guanghong Gong and Liang Han

      Article first published online: 24 NOV 2014 | DOI: 10.1002/cav.1625

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      An octree space partition is employed to subdivide vortex particles into individual groups. According to the inquired position, vortex particles in different groups are accumulated and composed as a single super vortex particle, so that the number of participated vortex particles is greatly decreased to reduce computational cost.

  2. Special Issue Papers

    1. Planning approaches to constraint-aware navigation in dynamic environments

      Kai Ninomiya, Mubbasir Kapadia, Alexander Shoulson, Francisco Garcia and Norman Badler

      Article first published online: 27 OCT 2014 | DOI: 10.1002/cav.1622

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      This paper presents a path planning framework that handles spatial constraints imposed upon the system. The type of constraints specified could include staying behind a building, walking along walls, or avoiding the line of sight of patrolling agents. We introduce two advanced environment representations that balance computational efficiency and search space density in constrained system. An extended anytime dynamic planner is used to compute constraint-aware paths while efficiently repairing solutions to account for varying dynamic constraints or an updating world model.

  3. Research Articles

    1. 3D street art illusions: embedding chalk stylized rendering of 3D objects into a pavement photo

      Der-Lor Way and Cheng-Han Hsieh

      Article first published online: 7 OCT 2014 | DOI: 10.1002/cav.1624

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      User inputs a photo and 3D model. First, a user needs to annotate two pairs of parallel lines in the street image. Then, two vanishing points are estimated for recovering the camera's position. The 3D models are rendered using the proposed chalk stylized rendering technique at the same camera position. Finally, the object's non-photorealistic rendered image is embedded into a street photo by using a modified Poisson blending approach.

    2. Interconnecting distributed virtual worlds using Metabots: performance evaluation against the traditional client-server model

      Theodore Kotsilieris, George T. Karetsos, Ioannis Anagnostopoulos and Nikoletta A. Dimopoulou

      Article first published online: 30 SEP 2014 | DOI: 10.1002/cav.1623

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      Virtual Worlds evolution is breaking the barriers of virtual isolation, whereas mobile agents have been established as a solid programming method for heterogeneous networking and computing environments. This article proposes a distributed Virtual World reference platform for enhanced users' experience. The concept of Metabot is used to demonstrate the convergence of software agents' characteristics with 3D World avatar attributes, and a relevant implementation scheme is presented along with experimental results that prove the performance enhancements achieved.

  4. Special Issue Papers

    1. Basis enrichment and solid–fluid coupling for model-reduced fluid simulation

      Dan Gerszewski, Ladislav Kavan, Peter-Pike Sloan and Adam W. Bargteil

      Article first published online: 12 SEP 2014 | DOI: 10.1002/cav.1612

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      We present several enhancements to dimensionally reduced fluid simulations: a basis enrichment scheme to mix data-driven and analytic modes, and a new approach to two-way solid-fluid coupling. Our enrichment scheme enables the combination of the generality of eigenmodes with the context awareness and art directability of data-driven modes. Our approach to solid-fluid coupling combines vortex panel methods for solid fluid coupling, dynamic pressure for fluid solid coupling, the method of images to handle domain boundaries, and a quadtree-based method to accelerate the solid fluid coupling.

  5. Research Articles

    1. Position-based rigid-body dynamics

      Crispin Deul, Patrick Charrier and Jan Bender

      Article first published online: 5 SEP 2014 | DOI: 10.1002/cav.1614

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      We propose a stable position-based approach for large-scale simulations of rigid bodies at interactive frame rates. Our method solves positional constraints between rigid bodies and can therefore be seamlessly integrated into other position-based methods. Moreover, our approach supports the interaction of particles and rigid bodies by using common constraints, which allows for a two-way coupling with deformables.

    2. Combining inverse blending and Jacobian-based inverse kinematics to improve accuracy in human motion generation

      Liang Zhang and Guido Brunnett

      Article first published online: 5 SEP 2014 | DOI: 10.1002/cav.1615

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      We present a hybrid method for motion editing combining motion blending and Jacobian-based IK. A blending-based IK solver is first employed before the result is improved by a Jacobian-based IK solver, and a weight map is introduced to accelerate the searching in the weight space. With the proposed method, user defined constraints are satisfied accurately, and the resulting motions are realistic even when extrapolations are required.

    3. Corruptible social agents

      J. Octavio Gutierrez-Garcia and Luis-Felipe Rodríguez

      Article first published online: 5 SEP 2014 | DOI: 10.1002/cav.1613

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      A belief-desire-intention framework for modeling corruptible social agents supported by (i) the functional event calculus and (ii) a fuzzy logic system for belief update is proposed. Results obtained from agent-based simulations show that (i) the bribery rate increases as more external entities attempt to bribe agents and (ii) the more anti-corruption factors agents believe to be true, the less prone to perpetrate acts of corruption.

  6. Special Issue Papers

    1. Dynamic sprites: artistic authoring of interactive animations

      Ben Jones, Jovan Popovic, James McCann, Wilmot Li and Adam Bargteil

      Article first published online: 28 JUL 2014 | DOI: 10.1002/cav.1608

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      Dynamic Ssprites combine artist input and physics based animation to create stylized, interactive objects for virtual environments.

  7. Research Articles

    1. Realistic and stable simulation of turbulent details behind objects in smoothed-particle hydrodynamics fluids

      Xuqiang Shao, Zhong Zhou, Jinsong Zhang and Wei Wu

      Article first published online: 28 JUL 2014 | DOI: 10.1002/cav.1607

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      This paper presents a novel realistic and stable turbulence synthesis method to simulate the turbulent details generated behind objects in SPH fluids. Moreover, in order to efficiently catch turbulent details for rendering, we propose an octree-based adaptive surface reconstruction method for particle-based fluids.

    2. Predicting audio step feedback for real walking in virtual environments

      Markus Zank, Thomas Nescher and Andreas Kunz

      Article first published online: 3 JUL 2014 | DOI: 10.1002/cav.1611

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      In order to increase immersion in virtual worlds, we present a novel method for triggering audio step feedback for real walking in virtual environments using accelerometers and gyroscopes attached to a user's feet in combination with a prediction method based on characteristic gait events. In this way, it is possible to trigger the playback of a synthetic step sound at the right time by predicting the correct time for the audio feedback from sensor data.

    3. Anticipated velocity based guidance strategy for wheeled mobile evader amidst stationary and moving obstacles in bounded environment

      Amit Kumar and Aparajita Ojha

      Article first published online: 30 JUN 2014 | DOI: 10.1002/cav.1609

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      This work is concerned with a class of pursuit-evasion game problems involving single pursuer and single evader. The environment is bounded and unknown to both players. In addition to this, static and dynamic obstacles are also present in the environment. A novel technique based on anticipated-velocity of the pursuer is proposed for a nonholonomic wheeled mobile evader to navigate and escape from the fast pursuer.

  8. Special Issue Papers

    1. Facetons: face primitives for building 3D architectural models in virtual environments

      Naoki Sasaki, Hsiang-Ting Chen, Daisuke Sakamoto and Takeo Igarashi

      Article first published online: 17 JUN 2014 | DOI: 10.1002/cav.1603

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      We present facetons, geometric modeling primitives designed for building architectural models especially effective for a virtual environment where six degrees of freedom input devices are available. A faceton is an oriented point floating in the air and defines a plane of infinite extent passing through the point. With the simple interaction of faceton, users can easily create 3D architecture models.

  9. Research Articles

    1. Efficient and effective cage generation by region decomposition

      Chuhua Xian, Guiqing Li and Yunhui Xiong

      Article first published online: 28 APR 2014 | DOI: 10.1002/cav.1571

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      Cage generation is important for cage-based deformation in computer animation. To build a proper cage, we use voxelization-based method to decompose the input model into broad and narrow regions and then construct partial cages using different strategies and unite them to get a cage. Experiment results demonstrate that our method is effective, efficient, and robust to model transformation.

    2. Generating a multiplicity of policies for agent steering in crowd simulation

      Cory D. Boatright, Mubbasir Kapadia, Jennie M. Shapira and Norman I. Badler

      Article first published online: 28 APR 2014 | DOI: 10.1002/cav.1572

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      Data from an offline planner is used to feed training samples into a machine learning process. A collection of policies are learned based on this data, creating steering similar to the slower process but capable of running at interactive framerates. Time was reduced from hours to 10 frames per second with orders of magnitude more agents.

    3. A geometric approach to animating thin surface features in smoothed particle hydrodynamics water

      Taekwon Jang and Junyong Noh

      Article first published online: 23 JAN 2014 | DOI: 10.1002/cav.1568

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      Explicit interparticle connections are created among smoothed particle hydrodynamics particles to animating thin surface features.

    4. Parallel-optimizing SPH fluid simulation for realistic VR environments

      Chen Huang, Jian Zhu, Hanqiu Sun and Enhua Wu

      Article first published online: 28 DEC 2013 | DOI: 10.1002/cav.1564

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      The paper presents a fast and parallel framework for fluid simulation and rendering for interactive virtual reality environments, including an efficient activity-based particle property reuse algorithm for large-scale simulation, and a parallel marching cubes based on histogram pyramid technique for fast fluid surface rendering.

  10. Special Issue Papers

    1. 3D shape retrieval using viewpoint information-theoretic measures

      Xavier Bonaventura, Jianwei Guo, Weiliang Meng, Miquel Feixas, Xiaopeng Zhang and Mateu Sbert

      Article first published online: 18 DEC 2013 | DOI: 10.1002/cav.1566

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      We present an information-theoretic framework to compute the shape similarity between 3D polygonal models. Three different methods are introduced to evaluate the shape similarity, and they are respectively based on the L2 distance between information spheres, the earth mover's distance between information histograms and the absolute difference between the mutual information of each model. The performance of these techniques is tested using the Princeton Shape Benchmark database.

  11. Research Articles

    1. Contour-based polygonal ambient occlusion using a single-depth texture

      Sang-Gil Lee and Byeong-Seok Shin

      Article first published online: 18 DEC 2013 | DOI: 10.1002/cav.1567

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      Our method is a new shading approach that uses a depth texture by adding the contour levels and the attenuation by distance. In this method, the contour level is an integer value derived from the depth difference at neighboring texels in the depth texture, with the geometry surrounding a surface point.

    2. You have full text access to this OnlineOpen article
      Physically-based forehead animation including wrinkles

      Mark Warburton and Steve Maddock

      Article first published online: 26 NOV 2013 | DOI: 10.1002/cav.1565

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      A fully physically-based animation approach is presented for efficiently producing realistic-looking animations of facial movement, including expressive wrinkles. Detailed voxel-based models are simulated using a graphics processing unit-based finite element solver. Our flexible approach enables different muscle structures and material parameters to be used, for example, to animate different aged skins.

    3. Analytical solutions for tree-like structure modelling using subdivision surfaces

      Xiaoqiang Zhu, Xiaogang Jin and Lihua You

      Article first published online: 26 NOV 2013 | DOI: 10.1002/cav.1563

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      Skeleton-based tree-like shapes modelling with subdivision surfaces. Closed-form solutions for reverse calculation of the control mesh for Catmull–Clark subdivision.

    4. Streaming 3D deforming surfaces with dynamic resolution control

      Lin Zhang, Fei Dou, Zhong Zhou and Wei Wu

      Article first published online: 26 NOV 2013 | DOI: 10.1002/cav.1562

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      In this paper, we introduce an efficient streaming framework based on a decomposing-reconstruction approach, which allows meshes with multi-resolutions to share the same animation simultaneously in real time. The main contribution in this paper are a receiver-based progressive mesh reconstruction approach and a progressive view-dependent technique for frame rate control, as well as an effective interpolation-based optimization approach. The experimental results show that our approach achieves very efficient performance even when deformations of large 3D models are streamed among remote users.

    5. A local adaptive Catmull–Rom to reduce numerical dissipation of semi-Lagrangian advection

      Zhanpeng Huang, Liang Han and Guanghong Gong

      Article first published online: 11 OCT 2013 | DOI: 10.1002/cav.1559

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      The adaptive interpolation clamps undershoots and overshoots selectively to overcome the excessively flattening problem of monotonic Catmull–Rom. The new scheme obtains the same accurate as monotonic Catmull–Rom but conserves the diversity of flow to recover details features of fluid motion. It is easy to integrate to existing fluid simulators.

    6. Fast animation of debris flow with mixed adaptive grid refinement

      Changbo Wang, Qiang Zhang, Fanlong Kong and Yusheng Gao

      Article first published online: 10 AUG 2013 | DOI: 10.1002/cav.1542

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      A highly effective method of modeling and animating of debris flow with adaptive grid is presented. With the view-dependent adaptive and boundless grids, two-way coupling interaction between flows and environment is modeled. Different dynamic realistic debris flow scenes with enhanced details based on adaptive surface tension are successfully animating at interactive rates.

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