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Now showing 1 - 10 of 10
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    Dynamic Video Face Transformation Using Multilinear and Autoregressive Models
    (The Eurographics Association, 2011) Tiddeman, Bernard; Hunter, David; Perrett, David; Ian Grimstead and Hamish Carr
    In this paper we present a prototype system for altering perceived attributes of faces in video sequences, such as the apparent age, sex or emotional state. The system uses multilinear models to decompose the parameters coding for each frame into separate pose and identity parameters. The multilinear model is learnt automatically from the training video data. Statistical models of group identity are then used to alter the identity parameters from one group to another (e.g. from male to female). An autoregressive model is learnt from the pose parameters, and this is applied to alter the dynamics. We have tested our system on a small dataset (for altering apparent gender) with encouraging preliminary results.
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    Linear-Time Dynamics for Multibody Systems with General Joint Models
    (The Eurographics Association, 2010) Si, Weiguang; Guenter, Brian; MZoran Popovic and Miguel Otaduy
    Most current linear-time forward dynamics algorithms support only simple types of joints due to difficulties in computing derivatives of joint transformations up to order two.We apply the D* symbolic differentiation algorithm to a recursive formulation of forward dynamics to get a highly efficient linear-time forward dynamics algorithm supporting multibody systems with general scleronomic joints. With this new algorithm we can easily build a treetopology multibody system with complex joint models and perform forward dynamics efficiently. The source code for the algorithm is freely available for non-commercial use.
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    Facial Retargeting by Adding Supplemental Blendshapes
    (The Eurographics Association, 2011) Kim, Paul Hyunjin; Seol, Yeongho; Song, Jaewon; Noh, Junyong; Bing-Yu Chen and Jan Kautz and Tong-Yee Lee and Ming C. Lin
    This paper introduces a novel method to add a minimal set of missing blendshapes to automatically improve the quality of the retargeting result. Our approach compares the expression spaces defined by the source and the target to determine which frames need to be corrected. The expression spaces are represented on the principal axes extracted from the target blendshapes. Those frames that cannot be sufficiently reconstructed by the current set of blendshapes will be augmented by a set of automatically generated blendshapes. The new blendshapes are determined to minimize error between the source animation and the retargeting result. We performed experiments to compare the results created by a basic set of blendshapes and by our method. Our method effectively reduces error between the source and target animation, and produces much visually improved target animation without relying on manual intervention.
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    Interactive Simulation of a Continuum Mechanics based Torsional Thread
    (The Eurographics Association, 2010) Larsson, Karl; Wallgren, Göran; Larson, Mats G.; Kenny Erleben and Jan Bender and Matthias Teschner
    This paper introduces a continuum mechanics based thread model for use in real-time simulation. The model includes both rotary inertia, shear deformation and torsion. It is based on a three-dimensional beam model, using a corotational approach for interactive simulation speeds as well as adaptive mesh resolution to maintain accuracy. Desirable aspects of this model from a numerical and implementation point of view include a true constant and symmetric mass matrix, a symmetric and easily evaluated tangent stiffness matrix, and easy implementation of time-stepping algorithms. From a modeling perspective interesting features are deformation of the thread cross section and the use of arbitrary cross sections without performance penalty.
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    A Fast Simulation Method Using SPH and Wavelet for Sub-Particle-Scale Turbulent Flow
    (The Eurographics Association, 2011) Fujisawa, Makoto; Mimura, Go; Amano, Toshiyuki; Miyazaki, Jun; Kato, Hirokazu; Bing-Yu Chen and Jan Kautz and Tong-Yee Lee and Ming C. Lin
    This paper presents a fast simulation method for turbulent flow which uses a particle method and wavelet analysis. To simulate fluid flow, the method uses smoothed particle hydrodynamics (SPH), which discretizes the fluid into a collection of particles, and detects regions where turbulent flow will occur by using wavelet analysis without a spatial grid. By taking the curl of wavelet noise, the turbulent flow is then appended as a divergence-free turbulence velocity field. Additionally, by using vortex subparticles, which characterize the vortex features of turbulence, a subparticle-scale representation of turbulent flow is proposed. Implementing almost all processes on a graphics processing unit (GPU), simulations are performed in near real time.
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    Animating Non-Humanoid Characters with Human Motion Data
    (The Eurographics Association, 2010) Yamane, Katsu; Ariki, Yuka; Hodgins, Jessica; MZoran Popovic and Miguel Otaduy
    This paper presents a method for generating animations of non-humanoid characters from human motion capture data. Characters considered in this work have proportion and/or topology significantly different from humans, but are expected to convey expressions and emotions through body language that are understandable to human viewers. Keyframing is most commonly used to animate such characters. Our method provides an alternative for animating non-humanoid characters that leverages motion data from a human subject performing in the style of the target character. The method consists of a statistical mapping function learned from a small set of corresponding key poses, and a physics-based optimization process to improve the physical realism.We demonstrate our approach on three characters and a variety of motions with emotional expressions
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    Sketch-based Breaking Waves
    (The Eurographics Association, 2011) Zhang, Guijuan; Wen, Gaojin; Zhu, Dengming; Lu, Dianjie; Feng, Shengzhong; Bing-Yu Chen and Jan Kautz and Tong-Yee Lee and Ming C. Lin
    We present a sketching method for animating breaking waves in this paper. Our approach allows an animator to control physically-based wave breaking effects by drawing the outline of the wave shape intuitively. To do this, we provide a feature-based keyframe design model. We can sketch the wave shape roughly and describe the wave shape as a unified volume representation. Moreover, we propose an efficient keyframe matching model to transport current fluid state to the target state with minimum energy. The solution to the keyframe matching model is used to compute the external force field for the Navier-Stokes equations. Our method is straightforward to implement and convenient to produce interesting wave breaking behaviors. The experimental results show that our method is easy and intuitive to use.
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    Control Systems for Human Running using an Inverted Pendulum Model and a Reference Motion Capture Sequence
    (The Eurographics Association, 2010) Kwon, Taesoo; Hodgins, Jessica; MZoran Popovic and Miguel Otaduy
    Physical simulation is often proposed as a way to generate motion for interactive characters. A simulated character has the potential to adapt to changing terrain and disturbances in a realistic and robust manner. In this paper, we present a balancing control algorithm based on a simplified dynamic model, an inverted pendulum on a cart. The simplified model lacks the degrees of freedom found in a full human model, so we analyze a captured reference motion in a preprocessing step and use that information about human running patterns to supplement the balance algorithms provided by the inverted pendulum controller. At run-time, the controller plans a desired motion at every frame based on the current estimate of the pendulum state and a predicted pendulum trajectory. By tracking this time-varying trajectory, our controller creates a running character that dynamically balances, changes speed and makes turns. The initial controller can be optimized to further improve the motion quality with an objective function that minimizes the difference between a planned desired motion and a simulated motion. We demonstrate the power of this approach by generating running motions at a variety of speeds (3m/s to 5m/s), following a curved path, and in the presence of disturbance forces and a skipping motion.
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    Shortest Paths with Arbitrary Clearance from Navigation Meshes
    (The Eurographics Association, 2010) Kallmann, Marcelo; MZoran Popovic and Miguel Otaduy
    This paper addresses the problem of efficiently computing optimal paths of arbitrary clearance from a polygonal representation of a given virtual environment. Key to the proposed method is a new type of triangulated navigation mesh, called a Local Clearance Triangulation, which enables the efficient and correct determination if a disc of arbitrary size can pass through any narrow passages of the mesh. The proposed approach uniquely balances speed of computation and optimality of paths by first computing high-quality locally shortest paths efficiently in optimal time. Only in case global optimality is needed, an extended search will gradually improve the current path (if not already the global optimal) until the globally shortest one is determined. The presented method represents the first solution correctly extracting shortest paths of arbitrary clearance directly from a triangulated environment.
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    Real-time Rendering of Endless Cloud Animation
    (The Eurographics Association, 2011) Iwasaki, Kei; Nishino, Takanori; Dobashi, Yoshinori; Bing-Yu Chen and Jan Kautz and Tong-Yee Lee and Ming C. Lin
    In this paper, we propose a real-time animation method for dynamic clouds illuminated by sunlight and skylight with multiple scattering. In order to create animations of outdoor scenes, it is necessary to render time-varying dynamic clouds. However, the simulation and the radiance calculation of dynamic clouds are computationally expensive. In order to address this problem, we propose an efficient method to create endless animations of dynamic clouds. The proposed method prepares a database of dynamic clouds consisting of a finite number of volume data. Using this database, volume data for the endless animation is generated at run time using the concept of Video Textures, and this data is rendered in real-time using GPU.