Computer Animation and Virtual Worlds

Cover image for Vol. 27 Issue 1

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

Edited By: Nadia Magnenat Thalmann and Daniel Thalmann

Impact Factor: 0.463

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

Online ISSN: 1546-427X

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  1. 1 - 20
  1. Special Issue Papers

    1. Multi-group motion planning in virtual environments

      Erion Plaku, Sara Rashidian and Stefan Edelkamp

      Article first published 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.

  2. Research Articles

    1. A scalable geometrical model for musculotendon units

      Francis Laclé and Nicolas Pronost

      Article first published online: 21 DEC 2015 | DOI: 10.1002/cav.1684

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      This paper focuses on combining, by a controllable enhancement process, a functional and biomechanical model of musculotendon units with its high resolution geometrical counterpart. The method was developed in order to be invariant to spatial and polygonal configurations, and to be scalable in both longitudinal and latitudinal directions.

    2. Segmentation-based skinning

      Jorge Eduardo Ramírez Flores and Antonio Susín Sánchez

      Article first published online: 21 DEC 2015 | DOI: 10.1002/cav.1687

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      In this paper, we propose an approach based on mesh segmentation for skinning and skeleton-driven animation. Our method is based in watershed segmentation to deal with characters in T-Pose and arbitrary poses; the segmentation is the core algorithm of our method; we use it to develop a simple weight that assigns the LBS deformation method and a modified version of the LBS that avoids the loss of volume (candy-wrapper artifact) in twist rotations.

    3. Interactive light source position estimation for augmented reality with an RGB-D camera

      Bastiaan J. Boom, Sergio Orts-Escolano, Xin X. Ning, Steven McDonagh, Peter Sandilands and Robert B. Fisher

      Article first published online: 8 DEC 2015 | DOI: 10.1002/cav.1686

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      A synthetic object (dragon, right) that is rendered into a real-world scene recorded with the RGB-D sensor, where the illumination and rendered shadow of the synthetic object are similar to the scene based on an estimated light source position determined using only the intensity image and depth information.

    4. A PDE-based head visualization method with CT data

      Congkun Chen, Yun Sheng, Fang Li, Guixu Zhang and Hassan Ugail

      Article first published online: 30 NOV 2015 | DOI: 10.1002/cav.1683

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      A partial differential equation (PDE)-based head visualization framework, in which we integrate both head surface reconstruction and volume rendering, is proposed in this paper. Taking advantage of the PDE method, which needs a small amount of boundary conditions, only a small number of head slices are used in our framework; thus, the PDE-based method can be efficient.

    5. Predictive compression of animated 3D models by optimized weighted blending of key-frames

      Mohammadali Hajizadeh and Hossein Ebrahimnezhad

      Article first published online: 26 NOV 2015 | DOI: 10.1002/cav.1685

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      We propose a key-frame-based technique for three-dimensional dynamic mesh compression. By linear combination of the key-frames using blending weights, we predict the vertex locations of the other frames. We present a novel method in order to compute the optimum blending weights, which allows prediction of vertex locations for non-key frames with the minimum number of key-frames. The residual prediction errors are finally quantized and encoded.

    6. 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.

    7. 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.

    8. 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.

    9. 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.

  3. 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.

  4. 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. 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.

    8. 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.

    9. 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.

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