35-Issue 7

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https://diglib.eg.org/handle/10.2312/2630929

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Browsing 35-Issue 7 by Subject "Animation"

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    Incremental Deformation Subspace Reconstruction
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Mukherjee, Rajaditya; Wu, Xiaofeng; Wang, Huamin; Eitan Grinspun and Bernd Bickel and Yoshinori Dobashi
    Recalculating the subspace basis of a deformable body is a mandatory procedure for subspace simulation, after the body gets modified by interactive applications. However, using linear modal analysis to calculate the basis from scratch is known to be computationally expensive. In the paper, we show that the subspace of a modified body can be efficiently obtained from the subspace of its original version, if mesh changes are small. Our basic idea is to approximate the stiffness matrix by its lowfrequency component, so we can calculate new linear deformation modes by solving an incremental eigenvalue decomposition problem. To further handle nonlinear deformations in the subspace, we present a hybrid approach to calculate modal derivatives from both new and original linear modes. Finally, we demonstrate that the cubature samples trained for the original mesh can be reused in fast reduced force and stiffness matrix evaluation, and we explore the use of our techniques in various simulation problems. Our experiment shows that the updated subspace basis still allows a simulator to generate visual plausible deformation effects. The whole system is efficient and it is compatible with other subspace construction approaches.
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    A Multilevel SPH Solver with Unified Solid Boundary Handling
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Takahashi, Tetsuya; Lin, Ming C.; Eitan Grinspun and Bernd Bickel and Yoshinori Dobashi
    We propose a geometric multilevel solver for efficiently solving linear systems arising from particle-based methods. To apply this method to particle systems, we construct the hierarchy, establish the correspondence between solutions at the particle and grid levels, and coarsen simulation elements taking boundary conditions into account. In addition, we propose a new solid boundary handling method to solve a pressure Poisson equation in a unified manner. We demonstrate that our method can handle general fluid simulation scenarios including two-way fluid-solid coupling, and the computational cost of this new solver scales nearly linearly with respect to the number of unknowns, unlike previous solvers for particle-based methods.
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    Spatial Matching of Animated Meshes
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Seo, Hyewon; Cordier, Frederic; Eitan Grinspun and Bernd Bickel and Yoshinori Dobashi
    This paper presents a new technique which makes use of deformation and motion properties between animated meshes for finding their spatial correspondences. Given a pair of animated meshes exhibiting a semantically similar motion, we compute a sparse set of feature points on each mesh and compute spatial correspondences among them so that points with similar motion behavior are put in correspondence. At the core of our technique is our new, dynamic feature descriptor named AnimHOG, which encodes local deformation characteristics. AnimHOG is ob-tained by computing the gradient of a scalar field inside the spatiotemporal neighborhood of a point of interest, where the scalar values are obtained from the deformation characteristic associated with each vertex and at each frame. The final matching has been formulated as a discreet optimization problem that finds the matching of each feature point on the source mesh so that the descriptor similarity between the corresponding feature pairs as well as compatibility and consistency as measured across the pairs of correspondences are maximized. Consequently, reliable correspondences can be found even among the meshes of very different shape, as long as their motions are similar. We demonstrate the performance of our technique by showing the good quality of matching results we obtained on a number of animated mesh pairs.