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36
Robust treatment of collisions, contact and friction for cloth animation
 ACM Transactions on Graphics
, 2002
"... We present an algorithm to efficiently and robustly process collisions, contact and friction in cloth simulation. It works with any technique for simulating the internal dynamics of the cloth, and allows true modeling of cloth thickness. We also show how our simulation data can be postprocessed wit ..."
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Cited by 234 (22 self)
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We present an algorithm to efficiently and robustly process collisions, contact and friction in cloth simulation. It works with any technique for simulating the internal dynamics of the cloth, and allows true modeling of cloth thickness. We also show how our simulation data can be postprocessed with a collisionaware subdivision scheme to produce smooth and interference free data for rendering.
Nonconvex rigid bodies with stacking
 ACM Trans. Graph
"... We consider the simulation of nonconvex rigid bodies focusing on interactions such as collision, contact, friction (kinetic, static, rolling and spinning) and stacking. We advocate representing the geometry with both a triangulated surface and a signed distance function defined on a grid, and this d ..."
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Cited by 90 (8 self)
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We consider the simulation of nonconvex rigid bodies focusing on interactions such as collision, contact, friction (kinetic, static, rolling and spinning) and stacking. We advocate representing the geometry with both a triangulated surface and a signed distance function defined on a grid, and this dual representation is shown to have many advantages. We propose a novel approach to time integration merging it with the collision and contact processing algorithms in a fashion that obviates the need for ad hoc threshold velocities. We show that this approach matches the theoretical solution for blocks sliding and stopping on inclined planes with friction. We also present a new shock propagation algorithm that allows for efficient use of the propagation (as opposed to the simultaneous) method for treating contact. These new techniques are demonstrated on a variety of problems ranging from simple test cases to stacking problems with as many as 1000 nonconvex rigid bodies with friction as shown in Figure 1.
UberFlow: A GPUBased Particle Engine
, 2004
"... We present a system for realtime animation and rendering of large particle sets using GPU computation and memory objects in OpenGL. Memory objects can be used both as containers for geometry data stored on the graphics card and as render targets, providing an effective means for the manipulation an ..."
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Cited by 76 (3 self)
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We present a system for realtime animation and rendering of large particle sets using GPU computation and memory objects in OpenGL. Memory objects can be used both as containers for geometry data stored on the graphics card and as render targets, providing an effective means for the manipulation and rendering of particle data on the GPU. To fully take advantage of this mechanism, efficient GPU realizations of algorithms used to perform particle manipulation are essential. Our system implements a versatile particle engine, including interparticle collisions and visibility sorting. By combining memory objects with floatingpoint fragment programs, we have implemented a particle engine that entirely avoids the transfer of particle data at runtime. Our system can be seen as a forerunner of a new class of graphics algorithms, exploiting memory objects or similar concepts on upcoming graphics hardware to avoid bus bandwidth becoming the major performance bottleneck.
Collisions and Perception
 ACM Transactions on Graphics
, 2001
"... Level of Detail (LoD) techniques for realtime... In this paper, we are particularly interested in the problem of realistic collision simulation in scenes where large numbers of objects are colliding and processing must occur in realtime. An interruptible and therefore degradable collision handling ..."
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Cited by 46 (4 self)
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Level of Detail (LoD) techniques for realtime... In this paper, we are particularly interested in the problem of realistic collision simulation in scenes where large numbers of objects are colliding and processing must occur in realtime. An interruptible and therefore degradable collision handling mechanism is used and the perceptual impact of this degradation is explored. We look for ways in which we can optimise the realism of such simulations and describe a series of psychophysical experiments that investigated different factors affecting collision perception, including eccentricity, separation, distractors, causality and accuracy of physical response. Finally, strategies for incorporating these factors into a perceptually adaptive realtime simulation of large numbers of visually similar objects are presented.
Asynchronous Variational Integrators
 ARCH. RATIONAL MECH. ANAL.
, 2003
"... We describe a new class of asynchronous variational integrators (AVI) for nonlinear elastodynamics. The AVIs are distinguished by the following attributes: (i) The algorithms permit the selection of independent time steps in each element, and the local time steps need not bear an integral relation t ..."
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Cited by 36 (9 self)
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We describe a new class of asynchronous variational integrators (AVI) for nonlinear elastodynamics. The AVIs are distinguished by the following attributes: (i) The algorithms permit the selection of independent time steps in each element, and the local time steps need not bear an integral relation to each other; (ii) the algorithms derive from a spacetime form of a discrete version of Hamilton’s variational principle. As a consequence of this variational structure, the algorithms conserve local momenta and a local discrete multisymplectic structure exactly. To guide the development of the discretizations, a spacetime multisymplectic formulation of elastodynamics is presented. The variational principle used incorporates both configuration and spacetime reference variations. This allows a unified treatment of all the conservation properties of the system. A discrete version of reference configuration is also considered, providing a natural definition of a discrete energy. The possibilities for discrete energy conservation are evaluated. Numerical tests reveal that, even when local energy balance is not enforced exactly, the global and local energy behavior of the AVIs is quite remarkable, a property which can probably be traced to the symplectic nature of the algorithm.
Fast Penetration Depth Computation for Physicallybased Animation
 of ETRI, FUB and UH on core experiment N2 on automatic segmentation of moving objects”. Doc. ISO/IEC JTC1/SC29/WG11 MPEG97/m2383
, 2002
"... We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral models for physicallybased animation. Given two overlapping polyhedra, it computes the minimal translation distance to separate them using a combination of objectspace and imagespace techniques. The alg ..."
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Cited by 35 (10 self)
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We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral models for physicallybased animation. Given two overlapping polyhedra, it computes the minimal translation distance to separate them using a combination of objectspace and imagespace techniques. The algorithm computes pairwise Minkowski sums of decomposed convex pieces and performs a closest point query using rasterization hardware. It uses bounding volume hierarchies, objectspace and imagespace culling algorithms to further accelerate the computation and refines the estimated PD in a hierarchical manner. We demonstrate its application to contact response computation and a timestepping method for dynamic simulation.
Evaluating the Visual Fidelity of Physically Based Animations
, 2003
"... For many systems that produce physically based animations, plausibility rather than accuracy is acceptable. We consider the problem of evaluating the visual quality of animations in which physical parameters have been distorted or degraded, either unavoidably due to realtime framerate requirements ..."
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Cited by 35 (3 self)
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For many systems that produce physically based animations, plausibility rather than accuracy is acceptable. We consider the problem of evaluating the visual quality of animations in which physical parameters have been distorted or degraded, either unavoidably due to realtime framerate requirements, or intentionally for aesthetic reasons. To date, no generic means of evaluating or predicting the fidelity, either physical or visual, of the dynamic events occurring in an animation exists. As a first step towards providing such a metric, we present a set of psychophysical experiments that established some thresholds for human sensitivity to dynamic anomalies, including angular, momentum and spatiotemporal distortions applied to simple animations depicting the elastic collision of two rigid objects. In addition to finding significant acceptance thresholds for these distortions under varying conditions, we identified some interesting biases that indicate nonsymmetric responses to these distortions (e.g., expansion of the angle between postcollision trajectories was preferred to contraction and increases in velocity were preferred to decreases). Based on these results, we derived a set of probability functions that can be used to evaluate the visual fidelity of a physically based simulation. To illustrate how our results could be used, two simple case studies of simulation levels of detail and constrained dynamics are presented.
OptimizationBased Animation
, 2002
"... A new paradigm for rigid body simulation is presented and analyzed. Current techniques for rigid body simulation run slowly on scenes with many bodies in close proximity. Each time two bodies collide or make or break a static contact, the simulator must interrupt the numerical integration of velocit ..."
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Cited by 35 (1 self)
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A new paradigm for rigid body simulation is presented and analyzed. Current techniques for rigid body simulation run slowly on scenes with many bodies in close proximity. Each time two bodies collide or make or break a static contact, the simulator must interrupt the numerical integration of velocities and accelerations. Even for simple scenes, the number of discontinuities per frame time can rise to the millions. An efficient optimizationbased animation (OBA) algorithm is presented which can simulate scenes with many convex threedimensional bodies settling into stacks and other “crowded” arrangements. This algorithm simulates Newtonian (second order) physics and Coulomb friction, and it uses quadratic programming (QP) to calculate new positions, momenta, and accelerations strictly at frame times. The extremely small integration steps inherent to traditional simulation techniques are avoided. Contact points are synchronized at the end of each frame. Resolving contacts with friction is known to be a difficult problem. Analytic force calculation can have ambiguous or nonexisting solutions. Purely impulsive techniques avoid these ambiguous cases, but still require an excessive and computationally expensive number of updates in the case of
Asynchronous contact mechanics
"... We develop a method for reliable simulation of elastica in complex contact scenarios. Our focus is on firmly establishing three parameterindependent guarantees: that simulations of wellposed problems (a) have no interpenetrations, (b) obey causality, momentum and energyconservation laws, and (c ..."
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Cited by 15 (5 self)
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We develop a method for reliable simulation of elastica in complex contact scenarios. Our focus is on firmly establishing three parameterindependent guarantees: that simulations of wellposed problems (a) have no interpenetrations, (b) obey causality, momentum and energyconservation laws, and (c) complete in finite time. We achieve these guarantees through a novel synthesis of asynchronous variational integrators, kinetic data structures, and a discretization of the contact barrier potential by an infinite sum of nested quadratic potentials. In a series of two and threedimensional examples, we illustrate that this method more easily handles challenging problems involving complex contact geometries, sharp features, and sliding during extremely tight contact.
Fast Penetration Depth Computation Using Rasterization Hardware and Hierarchical Refinement
, 2002
"... We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral models. Given two overlapping polyhedra, it computes the minimal translation distance to separate them using a combination of objectspace and imagespace techniques. The algorithm computes pairwise Minkow ..."
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Cited by 14 (9 self)
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We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral models. Given two overlapping polyhedra, it computes the minimal translation distance to separate them using a combination of objectspace and imagespace techniques. The algorithm computes pairwise Minkowski sums of decomposed convex pieces, performs closestpoint query using rasterization hardware and refines the estimated PD by objectspace walking. It uses bounding volume hierarchies, model simplification, objectspace and imagespace culling algorithms to further accelerate the computation and refines the estimated PD in a hierarchical manner. We highlight its performance on complex models and demonstrate its application to dynamic simulation and tolerance verification.