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 "Computer Graphics [I.3.5]"

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    Accurate Tangential Velocities For Solid Fluid Coupling
    (ACM SIGGRAPH / Eurographics Association, 2009) Robinson-Mosher, Avi; English, R. Elliot; Fedkiw, Ronald; Eitan Grinspun and Jessica Hodgins
    We propose a novel method for obtaining more accurate tangential velocities for solid fluid coupling. Our method works for both rigid and deformable objects as well as both volumetric objects and thin shells. The fluid can be either one phase such as smoke or two phase such as water with a free surface. The coupling between the solid and the fluid can either be one-way with kinematic solids or fully two-way coupled. The only previous scheme that was general enough to handle both two-way coupling and thin shells required a mass lumping strategy that did not allow for freely flowing tangential velocities. Similar to that previous work, our method prevents leaking of fluid across a thin shell, however unlike that work our method does not couple the tangential velocities in any fashion, allowing for the proper slip independently on each side of the body. Moreover, since it accurately and directly treats the tangential velocity, it does not rely on grid refinement to obtain a reasonable solution. Therefore, it gives a highly improved result on coarse meshes.
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    Anisotropic Friction for Deformable Surfaces and Solids
    (ACM SIGGRAPH / Eurographics Association, 2009) Pabst, Simon; Thomaszewski, Bernhard; Straßer, Wolfgang; Eitan Grinspun and Jessica Hodgins
    This paper presents a method for simulating anisotropic friction for deforming surfaces and solids. Frictional contact is a complex phenomenon that fuels research in mechanical engineering, computational contact mechanics, composite material design and rigid body dynamics, to name just a few. Many real-world materials have anisotropic surface properties. As an example, most textiles exhibit direction-dependent frictional behavior, but despite its tremendous impact on visual appearance, only simple isotropic models have been considered for cloth and solid simulation so far. In this work, we propose a simple, application-oriented but physically sound model that extends existing methods to account for anisotropic friction. The sliding properties of surfaces are encoded in friction tensors, which allows us to model frictional resistance freely along arbitrary directions. We also consider heterogeneous and asymmetric surface roughness and demonstrate the increased simulation quality on a number of two- and three-dimensional examples. Our method is computationally efficient and can easily be integrated into existing systems.
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    Energy Stability and Fracture for Frame Rate Rigid Body Simulations
    (ACM SIGGRAPH / Eurographics Association, 2009) Su, Jonathan; Schroeder, Craig; Fedkiw, Ronald; Eitan Grinspun and Jessica Hodgins
    Our goal is to design robust algorithms that can be used for building real-time systems, but rather than starting with overly simplistic particle-based methods, we aim to modify higher-end visual effects algorithms. A major stumbling block in utilizing these visual effects algorithms for real-time simulation is their computational intensity. Physics engines struggle to fully exploit available resources to handle high scene complexity due to their need to divide those resources among many smaller time steps, and thus to obtain the maximum spatial complexity we design our algorithms to take only one time step per frame. This requires addressing both accuracy and stability issues for collisions, contact, and evolution in a manner significantly different from a typical simulation in which one can rely on shrinking the time step to ameliorate accuracy and stability issues. In this paper we present a novel algorithm for conserving both energy and momentum when advancing rigid body orientations, as well as a novel technique for clamping energy gain during contact and collisions. We also introduce a technique for fast and realistic fracture of rigid bodies using a novel collision-centered prescoring algorithm.