Computer Animation and Virtual Worlds

Cover image for Vol. 26 Issue 5

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

Edited By: Nadia Magnenat Thalmann and Daniel Thalmann

Impact Factor: 0.463

ISI Journal Citation Reports © Ranking: 2014: 90/104 (Computer Science Software Engineering)

Online ISSN: 1546-427X


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  1. Research Articles

    1. Modeling flocks with perceptual agents from a dynamicist perspective

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

      Article first published online: 26 AUG 2015 | DOI: 10.1002/cav.1676

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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.

    2. Topology-aware moving least square deformation for 2D characters

      Xun Wang, Wenwu Yang, Wangbin Kou, Bailin Yang and Guozheng Wang

      Article first published online: 24 AUG 2015 | DOI: 10.1002/cav.1675

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      This paper presents a 2D MLS deformation method that takes into account the topology of the shape. The method allows the user to control shape deformation using either sets of points or line segments and is able to generate visually pleasing results where the possible distortion is effectively avoided. In addition, an area-preserving variant of the MLS deformation is proposed. This approach is simple and effective and is suitable for the editing of the incompressible objects.

    3. Assessing similarity models for human-motion retrieval applications

      Jakub Valcik, Jan Sedmidubsky and Pavel Zezula

      Article first published online: 24 AUG 2015 | DOI: 10.1002/cav.1674

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      Processing motion capture data requires an effective similarity model to extract suitable motion features along with their comparison method. However, it is hard to define the most appropriate model for the specific application. We try to solve this problem by proposing a generic framework (HAMMER) that assesses candidate similarity models on the basis of ground-truth data provided for the specific application.

    4. Character motion synthesis by principal component analysis and motion control interface by hands

      Masaki Oshita, Hayato Oshima, Yuta Senju and Syun Morishige

      Article first published online: 11 AUG 2015 | DOI: 10.1002/cav.1673

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      We propose an interactive character motion control interface that uses hands. We applied principal component analysis to a set of sample poses and assigned the extracted principal components to each degree of freedom of the hands (such as the hand positions and finger bending/extending angles). The user can control the blending weights of the principal components and deform the character's pose by moving their hands and bending/extending their fingers for altering the standing pose and performing various actions with deformations.

  2. Special Issue Papers

    1. Interest-driven avatar neighbor-organizing for P2P transmission in distributed virtual worlds

      Mingfei Wang, Jinyuan Jia, Ning Xie and Chenxi Zhang

      Article first published online: 28 JUL 2015 | DOI: 10.1002/cav.1670

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      This paper proposes a dynamic node-organizing mechanism that aims to solve neighbor table churning and frequent message exchanging in scene data transmission. We use an interest similarity-measuring algorithm to construct node clusters based on an avatar's behavioral characteristics and measure the cluster stability in terms of interest entropy, so as to maintain a stable neighbor mesh for each node. The experimental results show that our proposed mechanism enables us to improve the transmission efficiency significantly in distributed virtual environments.

  3. Research Articles

    1. Approximate resolution of asynchronous conflicts among sequential collaborations in dynamic virtual environments

      Jun Lee, Mingyu Lim, SungJun Park, HyungSeok Kim, Heedong Ko and Jee-In Kim

      Article first published online: 4 JUL 2015 | DOI: 10.1002/cav.1669

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      Our primary objective is to provide a semi-automatic resolution of the asynchronous conflicts using the relations of the affected objects. We develop a novel approximate resolution algorithm using a task-based modeling mechanism to resolve the asynchronous conflicts with their corresponding tasks. The participants can set flexible relations among shared objects. Following the setting of the relations, the proposed system detects asynchronous conflicts of the shared objects and resolves the conflicts automatically according to the predefined relations.

    2. Fast accessing Web3D contents using lightweight progressive meshes

      Laixiang Wen, Ning Xie and Jinyuan Jia

      Article first published online: 4 JUL 2015 | DOI: 10.1002/cav.1672

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      This paper proposes a similarity-aware data reduction method together with progressive meshes, called lightweight progressive meshes (LPM). LPM aims to excavate similar components in a 3D model, generates progressive meshes representation of each component left after removing redundant components, and organizes all the processed data using a structure called lightweight scene graph. Using LPM, the transmission of Web3D contents could be lightweight and progressive so that it is efficient and effective under limited bandwidth, especially when delivering large models.

    3. Graph-cut based interactive image segmentation with randomized texton searching

      Wei Ma, Yu Zhang, Luwei Yang and Lijuan Duan

      Article first published online: 20 JUN 2015 | DOI: 10.1002/cav.1671

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      A graph-cut-based interactive image-segmentation method is presented in this paper. It integrates texture constraints with color and gradient constraints in the framework of graph cut. In this method, a random texton-searching algorithm is presented to find representative textons for pixels. The textons are then used for construction of the texture constraints. Experimental results show that the proposed method outperforms state-of-the-art methods, especially in segmenting textured images.

    4. Interactive thin elastic materials

      Wen Tang, Tao Ruan Wan and Donjing Huang

      Article first published online: 5 JUN 2015 | DOI: 10.1002/cav.1666

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      Various strain-limiting thresholds produce different results for a thin sheet using a multi-resolution hierarchy. Images show final resting configurations of the finest mesh of the hierarchy. Four-level hierarchy is used with 20 iterations at each level. From left to right, strain-limiting values are[−20%,20%],[−10%,10%],[−5%,5%], and [−2%,2%], decreasing limiting thresholds that generated highly constrained material configuration with intricate surface details.

    5. Interactive constrained dynamics for rigid and deformable objects

      Luca Vezzaro, Davide Zerbato and Paolo Fiorini

      Article first published online: 5 JUN 2015 | DOI: 10.1002/cav.1667

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      Constraint-based approaches have seen widespread usage in interactive simulation of systems of either rigid or deformable objects, but not for the simultaneous simulation of both.We extended such techniques to fully support two-way interaction and explained how to develop different kinds of constraints, with a particular focus on contact response and friction. The method is easily integrated into existing physics engines that use similar constraint solvers and can be made to work with any kind of deformable object paradigm.

    6. Efficient level of detail for texture-based flow visualization

      Daying Lu, Dengming Zhu, Zhaoqi Wang and Jinzhu Gao

      Article first published online: 26 MAY 2015 | DOI: 10.1002/cav.1664

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      This paper proposes an efficient LOD control method for flow visualization through analyzing local similarity trends in movement patterns. Our method could adjust the point location and local region size automatically. We can also adjust the frequency spectrum of the noise texture under various viewing conditions, taking into account not only the depth distance of a sample point from the camera but also the contribution from the corresponding brick.

    7. Perceptual validity in animation of human motion

      S. Ali Etemad, Ali Arya, Avi Parush and Steve DiPaola

      Article first published online: 9 APR 2015 | DOI: 10.1002/cav.1631

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      A paradigm called perceptual validity, composed of four major components, is proposed. The model is concerned with different aspects of the scene such as correct illustration of the stimuli, context, and local/global relations of various visual cues present in human motion. The model is supported by examples from the literature and case studies. The relative significance of the different components of the paradigm is investigated and discussed in detail.

    8. Reconstructing 3D human models with a Kinect

      Guang Chen, Jituo Li, Bei Wang, Jiping Zeng, Guodong Lu and Dongliang Zhang

      Article first published online: 10 FEB 2015 | DOI: 10.1002/cav.1632

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      In this paper, we provide a method of reconstructing 3D naked human models for human bodies or dressed humans using the depth images captured by a single Kinect. The depth images from multi-views are part-wisely registered together, and implicit-surface-based de-noising method is put forward for the coarse data. Afterwards, we fit a statistical model to the registered depth image iteratively in order to obtain the reconstructed 3D human model and apply the reconstructed models in virtual try-on systems.

    9. Interactive digital graffiti canvas system

      Yong Sun Kim, Yongwan Kim and Ki-Hong Kim

      Article first published online: 9 FEB 2015 | DOI: 10.1002/cav.1633

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      The proposed interactive digital painting system provides a realistic graffiti experience in a virtual environment. Spray painting is simulated in real time with the pressure-sensitive, tracked digital spray can. The system visualizes a stereoscopic representation of the virtual environment by tracking the users' head and extends the viewing zone using an optical see-through head-mounted display.

    10. Efficient tetrahedral mesh generation based on sampling optimization

      Yuanfeng Zhou, Caiming Zhang and Pengbo Bo

      Article first published online: 2 FEB 2015 | DOI: 10.1002/cav.1628

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      We present a heuristic approach to tetrahedral mesh generation for implicit closed surfaces. It consists of a surface sampling step and a volume sampling step which both work in a unified optimization framework. Experimental results show that the new method can generate ideal tetrahedral meshes for closed implicit surfaces efficiently.

    11. Extending FABRIK with model constraints

      Andreas Aristidou, Yiorgos Chrysanthou and Joan Lasenby

      Article first published online: 2 FEB 2015 | DOI: 10.1002/cav.1630

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      This paper addresses the problem of manipulating articulated figures in an interactive and intuitive fashion for the design and control of their posture using the Forward and Backward Reaching Inverse Kinematics algorithm; the algorithm has been extended to support a variation of different joints and has been evaluated on a humanoid model.

    12. Towards more behaviours in crowd simulation

      Samuel Lemercier and Jean-Michel Auberlet

      Article first published online: 2 FEB 2015 | DOI: 10.1002/cav.1629

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      We aim at providing the pedestrian agent the ability to obtain an individual representation of the environment that allows it to adapt its behaviour according to the situation. We base our work on the analysis and interpretation of the environment, which makes the agent decide the behaviour it is going to adopt. We focus on two kinds of behaviours, following and group avoidance behaviours, and on their integration in classical avoidance simulations.

    13. 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.

    14. 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.

    15. 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.

    16. 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.

    17. 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.

    18. 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.

    19. 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.


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