Computer Animation and Virtual Worlds

Cover image for Vol. 27 Issue 3-4

May-August 2016

Volume 27, Issue 3-4

Pages 181–450

  1. Issue information

    1. Top of page
    2. Issue information
    3. Editorial
    4. Special Issue Papers
    1. Issue information (pages 181–182)

      Version of Record online: 20 MAY 2016 | DOI: 10.1002/cav.1721

  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. Real-time Simulation of Catheterization in Endovascular Surgeries (pages 185–194)

      Yanzhen Wang, Ferdinand Serracino-Inglott, Xiaodong Yi, Xue-Feng Yuan and Xue-Jun Yang

      Version of Record online: 11 MAY 2016 | DOI: 10.1002/cav.1702

      Thumbnail image of graphical abstract

      This paper proposes a numerical method for modeling catheterization during endovascular surgeries. A torsion free assumption is made for the underlying elastic rod model to increase the computational efficiency and numerical stability, and a volume-data-based contact handling algorithm is proposed to simulate the interaction between surgical wires and the aortic wall. The efficiency and effectiveness of the proposed method is validated and demonstrated by both quantitative evaluation and preliminary application in a prototype surgery simulation system.

    2. ACCLMesh: curvature-based navigation mesh generation (pages 195–204)

      Glen Berseth, Mubbasir Kapadia and Petros Faloutsos

      Version of Record online: 12 MAY 2016 | DOI: 10.1002/cav.1710

      Thumbnail image of graphical abstract

      The maturity of algorithms for pathfinding and local collision avoidance has paved the way for autonomous navigation and agent-based systems to prosper in complex environments. However, current solutions for computing a suitable representation of the navigable areas of these environments, which enables efficient pathfinding and collision avoidance, cannot handle unstructured, arbitrarily complex 3D environments. The proposed method computes a navigation mesh for arbitrary and dynamic 3D environments based on curvature.

    3. A path browser for exploratory motion assembly (pages 205–212)

      Kang Hoon Lee and Myung Geol Choi

      Version of Record online: 13 APR 2016 | DOI: 10.1002/cav.1692

      Thumbnail image of graphical abstract

      We present an interactive method for creating animation sequences of characters based on a path browser, which allows the user to visually examine a set of feasible connections between any two motion fragments instantiated in the space. With the aid of our path browser, the user can develop large-scale assembly of motions through iterations of arranging and putting together motion fragments in an exploratory way.

    4. Points-based user interface for character posing (pages 213–220)

      Myung Geol Choi and Kang Hoon Lee

      Version of Record online: 12 APR 2016 | DOI: 10.1002/cav.1693

      Thumbnail image of graphical abstract

      We present a points-based user interface for character posing. In our method, users insert a number of three-dimensional points in a virtual environment. The system searches a motion capture database for the best-matched pose, edits it to fit into the point constraints, and then places the pose immediately in the virtual environment to be overlapped with the input points.

    5. Data-driven detailed hair animation for game characters (pages 221–230)

      Chenlei Wu and Takashi Kanai

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1700

      Thumbnail image of graphical abstract

      We propose a data-driven method to realize high-quality detailed hair animations in interactive applications like games. By devising an error metric method to evaluate hair animation similarities, we take hair features into consideration as much as possible. We also propose a novel database construction algorithm based on Secondary Motion Graph. Our algorithm can improve the efficiency of such graphs to reduce redundant data and also achieves visually smooth connection of two animation clips while taking into consideration their future motions.

    6. An efficient GPU out-of-core framework for interactive rendering of large-scale CAD models (pages 231–240)

      Junjie Xue, Gang Zhao and Wenlei Xiao

      Version of Record online: 4 MAY 2016 | DOI: 10.1002/cav.1704

      Thumbnail image of graphical abstract

      This paper proposes an efficient graphics processing unit out-of-core framework for interactively visualizing large-scale computer-aided design models. An off-line geometry compression scheme is introduced to minimize the storage cost of each primitive. Occlusion culling and level of detail processing algorithms are integrated with an efficient graphics processing unit-based approach to determine a minimal scale of primitives to be transferred for each frame. The effectiveness and robustness of the framework are verified by testing on several computer-aided design models with hundreds of millions of triangles at high frame rates.

    7. Density-enhanced perceptual mosaic on GPU (pages 241–249)

      Ping Li and Hanqiu Sun

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1709

      Thumbnail image of graphical abstract

      This paper presents a density-enhanced perceptual mosaic using graphics processing unit parallelism, keeping the original image structure details well with density tiles replacement. Delicate brightness optimization and perceptual color correction are applied to enhance expressive lighting effects. Salience perception of images and similarity correlation among neighboring tiles are enhanced, providing expressive visual effects.

    8. Enhanced rig-space simulation (pages 250–261)

      Guiqing Li, Yaobin Ouyang, Guodong Wei, Zhibang Zhang and Aihua Mao

      Version of Record online: 20 MAY 2016 | DOI: 10.1002/cav.1705

      Thumbnail image of graphical abstract

      We allow user to define various fields, which are not necessarily conservative, on the mesh model to be simulated. We introduce proportional-derivative control to specify target rig-parameter trajectories and strength of control forces and therefore are able to trace the target trajectories as an entity. We improve the numerical stability for some tricky situations by prepending a conjugate gradient procedure to the original algorithm.

    9. Predictable behavior during contact simulation: a comparison of selected physics engines (pages 262–270)

      Se-Joon Chung and Nancy Pollard

      Version of Record online: 11 MAY 2016 | DOI: 10.1002/cav.1712

      Thumbnail image of graphical abstract

      Here, we present an extensive comparison of contact simulations using Bullet Physics, DART, MuJoCo, and Open Dynamics Engine, with a focus on predictability of behavior. We first tune each engine to match an analytical solution as closely as possible and then compare the results for a more complex simulation. Our results confirmed that parameter settings do matter a great deal, and suggest that there may be a trade-off between accuracy and predictability.

    10. Subtle features of ice with cloudy effects and scratches from collision damage (pages 271–279)

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

      Version of Record online: 19 APR 2016 | DOI: 10.1002/cav.1699

      Thumbnail image of graphical abstract

      We propose a simulation framework for expressing cloudy effects and scratches on ice caused by the collision of other objects. Cloudy effects are created and diffused in proportion to the collision on the ice surfaces calculated by a combination of a grid-projection technique and the boundary particle method. To prevent dissipation during the diffusion process, a geodesic distance is used as a constraint. Scratches are modeled directionally by analyzing the density gradient of cloudy effects and rendered using needle-shaped ellipsoids.

    11. Energized soft tissue dissection in surgery simulation (pages 280–289)

      Kun Qian, Tao Jiang, Meili Wang, Xiaosong Yang and Jianjun Zhang

      Version of Record online: 4 MAY 2016 | DOI: 10.1002/cav.1691

      Thumbnail image of graphical abstract

      We have proposed an energized soft tissue dissection model. We categorize the soft tissues into three types (fascia, membrane, and fat) and simulate their physical property accordingly. The dissection algorithm employs an edge-based structure, which offers an effective mechanism for the generation of incisions dissected with energized tools. Our dissection method is highly compatible and efficient to the physically based simulation resolved by a pre-factorized linear system.

    12. An interactive computer-based simulation system for endovascular aneurysm repair surgeries (pages 290–300)

      Yanzhen Wang, Ferdinand Serracino-Inglott, Xiaodong Yi, Xue-Jun Yang and Xue-Feng Yuan

      Version of Record online: 19 APR 2016 | DOI: 10.1002/cav.1713

      Thumbnail image of graphical abstract

      This paper presents an interactive computer-based simulation system for surgical procedures of endovascular aneurysm repair. It converts patient-specific medical imaging data into a personalized virtual surgical environment, upon which efficient and stable modeling methods are developed for real-time simulation of catheterization, angiography, and stent graft deployment operations. An interactive feature is achieved through multi-modal feedbacks including both visual and haptic renderings integrated with the simulation hardware platform

    13. Real-time facial expression transfer with single video camera (pages 301–310)

      Shuang Liu, Xiaosong Yang, Zhao Wang, Zhidong Xiao and Jianjun Zhang

      Version of Record online: 11 MAY 2016 | DOI: 10.1002/cav.1697

      Thumbnail image of graphical abstract

      We present a novel marker-less, real time facial transfer method that requires only a single video camera. We develop a robust model, which is adaptive to user-specific facial data. It computes expression variances in real time and rapidly transfers them onto a target character either from images or videos.

    14. Continuous body emotion recognition system during theater performances (pages 311–320)

      Simon Senecal, Louis Cuel, Andreas Aristidou and Nadia Magnenat-Thalmann

      Version of Record online: 12 MAY 2016 | DOI: 10.1002/cav.1714

      Thumbnail image of graphical abstract

      We present a continuous emotion recognition system with regard to body motion behavior analysis. Using a framework based on laban movement analysis principles, we map motion sequences, which have been captured using a low-cost motion capture device (Microsoft Kinect v2), onto a 2D emotion space coming from psychology studies.We evaluated our method on emotions expressed through theater performances, deploying a neural network that is able to guess the emotion corresponding to the body motion.

    15. Dance performance evaluation using hidden Markov models (pages 321–329)

      Sohaib Laraba and Joëlle Tilmanne

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1715

      Thumbnail image of graphical abstract

      In this work, we present a hidden Markov model-based system for gesture recognition and performance evaluation. The developed system is sensor-dependent and allows recognizing gestures recorded by a sensor, different than the one used for capturing the training dataset. An overall evaluation of the performance is estimated by calculating a score based on the outputted log-likelihood.

    16. Social context cognition crowd-sourcing and semi-automatic parametrization (pages 330–339)

      Jaroslaw Kochanowicz, Ah-Hwee Tan and Daniel Thalmann

      Version of Record online: 12 MAY 2016 | DOI: 10.1002/cav.1718

      Thumbnail image of graphical abstract

      This paper presents a semi-automatic method of parameterizing an existing social context cognition model. It discusses benefits of the social context cognition models, for example, in personality modeling and their key issue that is parametrization. It briefly introduces social context cognition model and describes a new method of its crowd-sourcing-based parametrization. Later, validation is provided, and ability to recreate social context cognition in the provided samples is presented with good generalization for the unknown cases. Finally, model's stability for the continuous stream of dynamic social context input data is shown. Presented system contributes to the believable agent modeling and social simulations by making much needed applications of social context cognition models easier by addressing the so far unsolved troublesome parametrization issues.

    17. DKD: a fast k-d tree update design for dynamic scenes (pages 340–350)

      Xin Yang, Qi Liu, Pengfei Zhang, Lutong Xin, Dongsheng Zhou, Yuxin Wang, Qiang Zhang and Xiaopeng Wei

      Version of Record online: 12 MAY 2016 | DOI: 10.1002/cav.1717

      Thumbnail image of graphical abstract

      We design dynamic k-d tree (DKD) based on classical k-d tree for animated scene rendering. Our method can inherit the benefit of efficient traversal of k-d tree and minimize time cost to update DKD. DKD employs primitive reset and redistribution to reflect the updated positions of geometry and leaf nodes incremental growing to avoid the deterioration of hierarchy quality due to refitting.

    18. Efficient view selection by measuring proxy information (pages 351–357)

      Tianhao Gao, Wencheng Wang and Honglei Han

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1698

      Thumbnail image of graphical abstract

      In comparison with the state-of-the-art techniques, our method can obtain very good views, although they are not only always ranked the best. Here, the views ranked the best and worst are marked in red and green boxes, respectively. As for the speed, we can obtain an acceleration of at least 180 times over mesh saliency (MS), view entropy (VE) and viewpoint saliency Kullback–Leibler distance (vSKL), several known fast methods for view selection.

    19. Efficient construction of bounding volume hierarchies into a complete octree for ray tracing (pages 358–368)

      Ulises Olivares, Héctor G. Rodríguez, Arturo García and Félix F. Ramos

      Version of Record online: 12 MAY 2016 | DOI: 10.1002/cav.1716

      Thumbnail image of graphical abstract

      This paper proposes an efficient construction scheme for bounding volume hierarchies based on a complete tree. This construction offers up to 4× faster construction times than binned-surface area hejristics and offers competitive ray traversal performance. The construction is fully parallelized on x86 CPU architectures, it takes advantage of the eight-wide vector units and exploits the advance vector extensions 2 available for current x86 CPU architectures. Additionally, this work presents a clustering algorithm for grouping primitives that can be computed in linear time.

    20. Walk the talk: coordinating gesture with locomotion for conversational characters (pages 369–377)

      Yingying Wang, Kerstin Ruhland, Michael Neff and Carol O'Sullivan

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1703

      Thumbnail image of graphical abstract

      Communicative behaviors are a very important aspect of human behavior and deserve special attention when simulating groups and crowds of virtual pedestrians. In this paper, we consider the problem of creating rich and varied conversational behaviors for data-driven animation of walking and jogging characters. Guided by ground truth metrics derived from real video, we perform stylized splicing and synchronization of gesture with locomotion to produce natural conversations of characters in motion.

    21. Online real-time locomotive motion transformation based on biomechanical observations (pages 378–384)

      Daseong Han, Seokpyo Hong, Junyong Noh, Xiaogang Jin and Joseph S. Shin

      Version of Record online: 19 APR 2016 | DOI: 10.1002/cav.1708

      Thumbnail image of graphical abstract

      In this paper, we present an online real-time method for automatically transforming a basic locomotive motion to a desired motion of the same type based on the following biomechanical observations: contact-driven center-of-mass control, anticipatory reorientation of upper body segments, moving speed adjustment, and whole-body leaning. Exploiting these observations, our method adds physical and behavioral naturalness to the resulting locomotive motions without preprocessing.

    22. Pipelining image compositing in heterogeneous networking environments (pages 385–393)

      Ning Liu, Dengming Zhu, Zhaoqi Wang, Hong Qin, Jianfeng Zhan and Jinzhu Gao

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1711

      Thumbnail image of graphical abstract

      This paper brings up a novel directional image compositing operator that takes the data flow direction into account when performing compositing. With this operator, we are able to find all the valid compositing pipelines for the participating nodes in heterogeneous environments. We also propose a dynamic programming based optimization algorithm that could get the optimal pipeline in polynomial time.

    23. Progressive light volume for interactive volumetric illumination (pages 394–404)

      Ning Liu, Dengming Zhu, Zhaoqi Wang, Yi Wei and Min Shi

      Version of Record online: 3 MAY 2016 | DOI: 10.1002/cav.1706

      Thumbnail image of graphical abstract

      This paper proposes a light volume-based volumetric illumination technique that can support advanced illumination effects like multi scattering in interactive applications. The light volume is built progressively such that our method can maintain an interactive frame rate. A progressive path tracer is used to render the final image based on the light volume.

    24. Physical-based spatio-temporal resolution enhancement of scalar data for fluid visualization (pages 405–414)

      Liqun Cui, Chunyong Ma and Ge Chen

      Version of Record online: 12 APR 2016 | DOI: 10.1002/cav.1694

      Thumbnail image of graphical abstract

      We present a method that improves the spatio-temporal resolution of fluid scalar data. In this method, velocity estimation is treated in a totally new way. We regard it as an inverse and optimized problem and reduce the calculation cost through convex optimization. Furthermore, we make the velocity field more accurate by coupling with Navier–Stokes equations.

    25. Data-driven projection method in fluid simulation (pages 415–424)

      Cheng Yang, Xubo Yang and Xiangyun Xiao

      Version of Record online: 5 MAY 2016 | DOI: 10.1002/cav.1695

      Thumbnail image of graphical abstract

      The simulation results using our data-driven projection method. It could speed up more than 10 times than preconditioned conjugate method.

    26. Real-time screen-space liquid rendering with complex refractions (pages 425–434)

      Takuya Imai, Yoshihiro Kanamori and Jun Mitani

      Version of Record online: 19 APR 2016 | DOI: 10.1002/cav.1707

      Thumbnail image of graphical abstract

      We present a screen-space method for rendering particle-based liquids with up to four refractions in real time. The key idea is to separate particles into splashes and aggregations, and to apply strong screen-space smoothing to depth maps obtained from particles. We can also consider the Beer-Lambert law for physically based light attenuation in liquids

    27. Interactive control of big-object manipulation animation (pages 435–442)

      Myung Geol Choi and Kang Hoon Lee

      Version of Record online: 14 APR 2016 | DOI: 10.1002/cav.1696

      Thumbnail image of graphical abstract

      We present a method for the interactive control of big-object manipulation animation. We first sample various postures that satisfy our feasibility conditions: collision free and physically stable. Then, we build a graph structure in which the nodes are the sampled postures and the links are collision-free motion interpolating between two-sampled postures. This manipulation motion graph allows us to use a general pathfinding method, such as Dijkstra's algorithm, to achieve real-time controllability.

    28. Let's be a virtual juggler (pages 443–450)

      Jong-In Choi, Sun-Jeong Kim, Chang-Hun Kim and Jung Lee

      Version of Record online: 12 APR 2016 | DOI: 10.1002/cav.1701

      Thumbnail image of graphical abstract

      We propose an interesting method to enable anyone to juggle skillfully in the virtual world. The user simply makes juggling-like motions in front of a motion sensor. Our system then searches for juggling motions that closely match the user's motions and connects them smoothly. We then generate moving objects that both satisfy the laws of physics and are synchronized with the synthesized motion of the avatar.

SEARCH

SEARCH BY CITATION