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Computer Animation and Virtual Worlds

Cover image for Vol. 26 Issue 3-4

May-August 2015

Volume 26, Issue 3-4

Pages i–ii, 195–481

  1. Issue Information

    1. Top of page
    2. Issue Information
    3. Editorial
    4. Special Issue Papers
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      Issue information (pages i–ii)

      Article first published online: 8 MAY 2015 | DOI: 10.1002/cav.1668

  2. Editorial

    1. Top of page
    2. Issue Information
    3. Editorial
    4. Special Issue Papers
    1. You have free access to this content
  3. Special Issue Papers

    1. Top of page
    2. Issue Information
    3. Editorial
    4. Special Issue Papers
    1. You have free access to this content
      Simultaneous estimation of elasticity for multiple deformable bodies (pages 197–206)

      Shan Yang and Ming Lin

      Article first published online: 8 MAY 2015 | DOI: 10.1002/cav.1649

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      Material property has great importance in deformable body simulation and medical robotics. We propose a novel elasticity estimation algorithm that can recover the elasticity parameters of multiple deformable bodies or multiple regions of one deformable body simultaneously from images. We validate our algorithm with both synthetic test cases and real patient computed tomography images.

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      Advanced ordinary differential equation based head modelling for Chinese marionette art preservation (pages 207–216)

      Hui Liang, Jian Chang, Xiaosong Yang, Lihua You, Shaojun Bian and Jian Jun Zhang

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1651

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      As an important pillar in Traditional Chinese marionette art, the head carving is of irreplaceable cultural and artistic values. This paper introduces a novel ordinary differential equation based modelling technique to model marionette head, which has been specially tailored to suit the modelling complexity and the need of accurate description of shapes. It offers smoothly sewing ordinary differential equation swept patches to represent the distinct features of a marionette head with sharp variance of local geometry.

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      Skill learning based catching motion control (pages 217–225)

      Gökçen Çimen, Zümra Kavafoǧlu, Ersan Kavafoǧlu, Tolga Çapın and Haşmet Gürcay

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1659

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      We present a real-time physics-based approach that generates natural and physically plausible ball catching motions. Such a complex task, like ball catching, can be achieved with the proper combination of rather simple motor skills, such as standing, walking, and reaching. We showed that correct planning of catching phases—ready, reaching, adapting, and catching—using reinforcement learning system can create accuracy in timing and realistic and natural look in animations.

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      Behavior generation for interactive virtual humans using context-dependent interaction meshes and automated constraint extraction (pages 227–235)

      David Vogt, Ben Lorenz, Steve Grehl and Bernhard Jung

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1648

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      In this paper, we propose several extensions to the interaction mesh approach based on statistical analyses of the underlying example interactions. By applying PCA and correlation analysis in addition to joint distance calculations, both the interaction mesh topology and the constraints used for mesh optimization can be generated in an automated fashion that accounts for the spatial and temporal contexts of the interaction.

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      PCMD: personality-characterized mood dynamics model toward personalized virtual characters (pages 237–245)

      Juzheng Zhang, Jianmin Zheng and Nadia Magnenat-Thalmann

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1660

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      Instead of heuristically designing behaviors for certain personalities, this paper bridges the gap between personalities and behaviors using a medium concept, mood. We propose a personality-characterized mood dynamics model, in which the overall mood approaches the personality after sufficient interactions to endow the virtual characters with consistent and flexible behavior patterns given certain personalities.

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      Dramaturgical and dissonance theories in explicit social context modeling for complex agents (pages 247–257)

      Jaroslaw Kochanowicz, Ah-Hwee Tan and Daniel Thalmann

      Article first published online: 8 MAY 2015 | DOI: 10.1002/cav.1639

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      Expanding the spectrum of agent social capabilities is an important challenge in agent-based simulation and other domains. While humanlike emotionality has been vastly explored in the last 20 years, little research addresses explicit, psychologically believable social situation modeling. In this paper, we develop a new approach to social situation modeling based on the dramaturgical and dissonance theories. A new component (Dramaturgical Module) is described with implementation used to generate example behavior depicting new social modeling capabilities.

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      SpaceTime: adaptive control of the teleported avatar for improved AR tele-conference experience (pages 259–269)

      Dongsik Jo, Ki-Hong Kim and Gerard Jounghyun Kim

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1645

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      This paper presents a novel method to first establish a spatial and object-level match between the remote and local sites and adapts the position and motion of the teleported avatar into the local AR space according to the matched information. This results in a natural looking and spatially correct rendering of the remote user in the local augmented space and a significantly improved tele-conference experience and communication performance.

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      Symmetric telepresence using robotic humanoid surrogates (pages 271–280)

      Arjun Nagendran, Anthony Steed, Brian Kelly and Ye Pan

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1638

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      In this manuscript, the authors explore the possibility of symmetric three-dimensional telepresence where both sides (participants) are “teleported” simultaneously to each other's location; the overarching concept of symmetric telepresence in virtual environments is extended to telepresence robots in physical environments. Results reveal that the symmetric robotic telepresence allowed participants to use and understand gestures in cases where they would otherwise have to describe their actions verbally.

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      Realistic and stable animation of cloth (pages 281–289)

      Junfeng Yao, Lei Lan, Wenlin Lin, Yingying She and Binbin Zhang

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1650

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      In this paper, we describe a realistic and stable scheme for cloth simulation based on mass-spring system. We modify the semi-implicit integration method and replace the original internal damping term with iterative spring damping forces. The experiments show that our cloth-simulation system can achieve unconditionally stable and much realism.

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      Garment capture from a photograph (pages 291–300)

      Moon-Hwan Jeong, Dong-Hoon Han and Hyeong-Seok Ko

      Article first published online: 4 MAY 2015 | DOI: 10.1002/cav.1653

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      Our paper proposed a novel method that can create the virtual garment from a single photograph of a real garment. We obtain the insight from the pattern drafting theory in the fashion field.

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      Effective skeletons extraction for animated surfaces based on geometry propagation (pages 301–309)

      Zhiqiang Pang, Yong Zhao and Chunxia Xiao

      Article first published online: 8 MAY 2015 | DOI: 10.1002/cav.1658

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      We introduce a registration-based propagation strategy to extract temporally coherent skeletons from the animated surfaces, develop a spatiotemporal L1-medial skeleton extraction method to extract the skeleton branches from the animated surfaces, and present a global skeleton alignment method, which effectively warps the key skeleton to the initial skeletons.

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      Image-inspired haptic interaction (pages 311–319)

      Xingzi Zhang and Alexei Sourin

      Article first published online: 4 MAY 2015 | DOI: 10.1002/cav.1643

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      We convert ordinary photos into tangible images, which can be then haptically rendered. This is performed interactively by augmenting images with haptic models defined in a 3D haptic modelling space distorted by the central projection. The tangible images thus created can realistically simulate actual 3D scenes by implementing the principle “What You See Is What You Touch” while in fact still be 2D images.

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      Real-time haptic manipulation and cutting of hybrid soft tissue models by extended position-based dynamics (pages 321–335)

      Junjun Pan, Junxuan Bai, Xin Zhao, Aimin Hao and Hong Qin

      Article first published online: 22 APR 2015 | DOI: 10.1002/cav.1655

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      Our dissection method uses a hybrid geometric model comprising both surface and volumetric meshes. An extended position-based dynamics approach that supports topology modification and material heterogeneities of soft tissue is presented as the physical model of soft tissues. Besides stretching and volume conservation constraints, this method enforces energy-preserving constraints, which takes the different spring stiffness of material into account and improves the visual performance of soft tissue deformation.

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      GPU-assisted real-time coupling of blood flow and vessel wall (pages 337–345)

      Jiaxiang Guo, Zhiyong Yuan, Xiangyun Liao, Yaoyi Bai and Qianfeng Lai

      Article first published online: 6 MAY 2015 | DOI: 10.1002/cav.1641

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      We present a new approach to solve non-Newtonian viscous force of blood and a parallel mixed particles-based coupling method for blood flow and vessel wall. Meanwhile, we also design a proxy particle-based vessel wall force visualization method.

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      Muddy water animation with different details (pages 347–355)

      Seungho Baek, Kiwon Um and JungHyun Han

      Article first published online: 22 APR 2015 | DOI: 10.1002/cav.1646

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      In this manuscript, we propose the particle-based method to simulate muddy water effects, which are readily observed at locations such as puddles and shorelines. Muddy water is an example of suspension, which is a mixture containing particles that separate into distinct layers if left undisturbed. For this phenomenon, we classified the mud particles into three types and proposed different simulation methods for the types.

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      SPH fluid control with self-adaptive turbulent details (pages 357–366)

      Xiaoyong Zhang and Shiguang Liu

      Article first published online: 4 MAY 2015 | DOI: 10.1002/cav.1637

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      This paper presents a novel self-adaptive control method for SPH fluid. Our method can randomly generate turbulence and effectively prevent the lack of fluid dynamics caused by the artificial viscosity. Experiment results show that our method improves the visual quality of the fluid animation, while greatly preserving the details of the target shape.

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      Adaptive cloud simulation using position based fluids (pages 367–375)

      Charles Welton Ferreira Barbosa, Yoshinori Dobashi and Tsuyoshi Yamamoto

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1657

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      Animation of clouds with particle-based simulation and adaptive splitting of particles.

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      Environment optimization for crowd evacuation (pages 377–386)

      Glen Berseth, Muhammad Usman, Brandon Haworth, Mubbasir Kapadia and Petros Faloutsos

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1652

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      Building layout has a significant impact on the flow patterns of its intended users. We propose a simulation framework that can be used to study the optimal placement of architectural elements, such as pillars or doors, for the purposes of facilitating dense pedestrian flow during the evacuation of a building. Our findings show that the optimal environment configuration depends on the nature of the collision avoidance algorithm used, and there is no single optimal solution for different crowd densities and flow patterns.

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      Guidance path scheduling using particle swarm optimization in crowd simulation (pages 387–395)

      Sai-Keung Wong, Pao-Kun Tang, Fu-Shun Li, Zong-Min Wang and Shih-Ting Yu

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1636

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      We propose a method for using particle swarm optimization (PSO) to compute optimal guidance paths for crowd in an agent-based simulation. The inputs of our system are guidance paths that provide hints for the movement directions of agents. Our method adjusts the guidance paths by using PSO based on a fitness function defined by the users.

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      An efficient lane model for complex traffic simulation (pages 397–403)

      Tianlu Mao, Hua Wang, Zhigang Deng and Zhaoqi Wang

      Article first published online: 8 MAY 2015 | DOI: 10.1002/cav.1642

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      This paper presents a novel method to model lanes based on the road axis under the Frenet frame. It couples mileage information with three-dimensional geometric information and keeps strictly consistent for mileage among neighboring lanes, so that is more functional and more efficient, especially for complex traffic simulation with a large number of lane-changes.

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      Vehicle–pedestrian interaction for mixed traffic simulation (pages 405–412)

      Qianwen Chao, Zhigang Deng and Xiaogang Jin

      Article first published online: 22 APR 2015 | DOI: 10.1002/cav.1654

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      Our approach aims to capture the realistic process of vehicle-pedestrian interaction for mixed traffic simulation. We model a decision-making process for their interaction based on a gap-acceptance judging criterion, and then design a novel environmental feedback mechanism for both vehicles' and pedestrians' behavior-control models to drive their motions. We demonstrate that our proposed method can soundly model vehicle-pedestrian interaction behaviors in a realistic and efficient manner and is convenient to be plugged into various traffic simulation systems.

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      Hybrid-based snow simulation and snow rendering with shell textures (pages 413–421)

      Sai-Keung Wong and I-Ting Fu

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1644

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      Snow is modeled as a hybrid structure that handles movable snow and static snow separately. Movable snow is represented by a set of particles, whereas static snow is modeled as grid cells. For a piece of movable snow (e.g., snowflake), the particles are connected using springs. To render the snow, we adopt a shell structure that has a series of concentric, semitransparent, and textured shells.

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      Interactive tree modeling and deformation with collision detection and avoidance (pages 423–432)

      Yong-Joon Kim, Jong-Hwa Woo, Myung-Soo Kim and Gershon Elber

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1661

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      We present an interactive tree modeling and deformation system that supports an efficient collision detection and avoidance using a bounding volume hierarchy of sweep surfaces. Starting with conventional tree models (given as meshes), we convert them into sweep-surfaces and deform their branches interactively while detecting and avoiding collisions with many other branches.

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      Boundary-dominant flower blooming simulation (pages 433–443)

      Jianfang Li, Min Liu, Weiwei Xu, Haiyi Liang and Ligang Liu

      Article first published online: 22 APR 2015 | DOI: 10.1002/cav.1647

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      This paper presents a new method based on a recent biological observation that flower opening is caused by a boundary-dominant morphological transition in a curved lamina. By controlling the in-plane expansion and out-of-plane curl growth, realistic and convincing flower blooming results are generated.

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      Giant soap bubble creation model (pages 445–455)

      Namjung Kim, SaeWoon Oh and Kyoungju Park

      Article first published online: 29 APR 2015 | DOI: 10.1002/cav.1640

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      Unlike small spherical soap bubbles, giant soap bubbles stretch significantly and undergo globally varying and locally consistent deformations because of time-varying surface tensions. Our Gibbs elasticity-based and Marangoni elasticity-based deformable model enables physical behaviors that evolve into a minimal surface exhibiting capillary waves, oscillating motion, and standing waves on the giant soap bubbles over time.

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      Controllable data sampling in the space of human poses (pages 457–467)

      Kyungyong Yang, Kibeom Youn, Kyungho Lee and Jehee Lee

      Article first published online: 8 MAY 2015 | DOI: 10.1002/cav.1662

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      Recent markerless pose recognition algorithms have adopted machine learning techniques, utilizing a large collection of motion capture data. We present a new sampling method that resamples a collection of human motion data to improve the pose variability and achieve an arbitrary size and level of density in the space of human poses. The recognition algorithm can also be steered to maximize its performance for a specific domain of human poses.

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      Efficient sketch-based creation of detailed character models through data-driven mesh deformations (pages 469–481)

      Ismail Khalid Kazmi, Lihua You, Xiaosong Yang, Xiaogang Jin and Jian J. Zhang

      Article first published online: 4 MAY 2015 | DOI: 10.1002/cav.1656

      Thumbnail image of graphical abstract

      Our proposed approach includes using user's drawn sketches to retrieve a most similar 3D template model from our dataset and marrying human's perception and interactions with computer's highly efficient computing to extract occluding and silhouette contours of the 3D template model and find correct correspondences quickly. We then combine skeleton-based deformation and mesh editing to deform the 3D template model to fit user's drawn sketches and create new and detailed 3D character models.

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