SCA 09: Eurographics/SIGGRAPH Symposium on Computer Animation

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https://diglib.eg.org/handle/10.2312/427

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Browsing SCA 09: Eurographics/SIGGRAPH Symposium on Computer Animation by Subject "based simulation"

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    A Point-Based Method for Animating Elastoplastic Solids
    (ACM SIGGRAPH / Eurographics Association, 2009) Gerszewski, Dan; Bhattacharya, Haimasree; Bargteil, Adam W.; Eitan Grinspun and Jessica Hodgins
    In this paper we describe a point-based approach for animating elastoplastic materials. Our primary contribution is a simple method for computing the deformation gradient for each particle in the simulation. The deformation gradient is computed for each particle by finding the affine transformation that best approximates the motion of neighboring particles over a single timestep. These transformations are then composed to compute the total deformation gradient that describes the deformation around a particle over the course of the simulation. Given the deformation gradient we can apply arbitrary constitutive models and compute the resulting elastic forces. Our method has two primary advantages: we do not store or compare to an initial rest configuration and we work directly with the deformation gradient. The first advantage avoids poor numerical conditioning and the second naturally leads to a multiplicative model of deformation appropriate for finite deformations. We demonstrate our approach on a number of examples that exhibit a wide range of material behaviors.
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    A Point-based Method for Animating Incompressible Flow
    (ACM SIGGRAPH / Eurographics Association, 2009) Sin, Funshing; Bargteil, Adam W.; Hodgins, Jessica K.; Eitan Grinspun and Jessica Hodgins
    In this paper, we present a point-based method for animating incompressible flow. The advection term is handled by moving the sample points through the flow in a Lagrangian fashion. However, unlike most previous approaches, the pressure term is handled by performing a projection onto a divergence-free field. To perform the pressure projection, we compute a Voronoi diagram with the sample points as input. Borrowing from Finite Volume Methods, we then invoke the divergence theorem and ensure that each Voronoi cell is divergence free. To handle complex boundary conditions, Voronoi cells are clipped against obstacle boundaries and free surfaces. The method is stable, flexible and combines many of the desirable features of point-based and grid-based methods. We demonstrate our approach on several examples of splashing and streaming liquid and swirling smoke.