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Collision Detection for Deformable Objects
"... Interactive environments for dynamically deforming objects play an important role in surgery simulation and entertainment technology. These environments require fast deformable models and very efficient collision handling techniques. While collision detection for rigid bodies is wellinvestigated, c ..."
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Cited by 119 (19 self)
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Interactive environments for dynamically deforming objects play an important role in surgery simulation and entertainment technology. These environments require fast deformable models and very efficient collision handling techniques. While collision detection for rigid bodies is wellinvestigated, collision detection for deformable objects introduces additional challenging problems. This paper focuses on these aspects and summarizes recent research in the area of deformable collision detection. Various approaches based on bounding volume hierarchies, distance fields, and spatial partitioning are discussed. Further, imagespace techniques and stochastic methods are considered. Applications in cloth modeling and surgical simulation are presented.
A Virtual Node Algorithm for Changing Mesh Topology during Simulation
 ACM Trans. Graph. (SIGGRAPH Proc
, 2004
"... We propose a virtual node algorithm that allows material to separate along arbitrary (possibly branched) piecewise linear paths through a mesh. The material within an element is fragmented by creating several replicas of the element and assigning a portion of real material to each replica. This resu ..."
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Cited by 82 (6 self)
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We propose a virtual node algorithm that allows material to separate along arbitrary (possibly branched) piecewise linear paths through a mesh. The material within an element is fragmented by creating several replicas of the element and assigning a portion of real material to each replica. This results in elements that contain both real material and empty regions. The missing material is contained in another copy (or copies) of this element. Our new virtual node algorithm automatically determines the number of replicas and the assignment of material to each. Moreover, it provides the degrees of freedom required to simulate the partially or fully fragmented material in a fashion consistent with the embedded geometry. This approach enables efficient simulation of complex geometry with a simple mesh, i.e. the geometry need not align itself with element boundaries. It also alleviates many shortcomings of traditional Lagrangian simulation techniques for meshes with changing topology. For example, slivers do not require small CFL time step restrictions since they are embedded in well shaped larger elements. To enable robust simulation of embedded geometry, we propose new algorithms for handling rigid body and self collisions. In addition, we present several mechanisms for influencing and controlling fracture with grain boundaries, prescoring, etc. We illustrate our method for both volumetric and thinshell simulations.
Position Based Dynamics
, 2006
"... The most popular approaches for the simulation of dynamic systems in computer graphics are force based. Internal and external forces are accumulated from which accelerations are computed based on Newton’s second law of motion. A time integration method is then used to update the velocities and final ..."
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Cited by 82 (2 self)
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The most popular approaches for the simulation of dynamic systems in computer graphics are force based. Internal and external forces are accumulated from which accelerations are computed based on Newton’s second law of motion. A time integration method is then used to update the velocities and finally the positions of the object. A few simulation methods (most rigid body simulators) use impulse based dynamics and directly manipulate velocities. In this paper we present an approach which omits the velocity layer as well and immediately works on the positions. The main advantage of a position based approach is its controllability. Overshooting problems of explicit integration schemes in force based systems can be avoided. In addition, collision constraints can be handled easily and penetrations can be resolved completely by projecting points to valid locations. We have used the approach to build a real time cloth simulator which is part of a physics software library for games. This application demonstrates the strengths and benefits of the method.
Capturing and animating occluded cloth
 ACM Trans. on Graphics (Proc. of ACM SIGGRAPH
, 2007
"... Figure 1: We reconstruct a stationary sleeve using thousands of markers to estimate the geometry (texture added with bump mapping). We capture the shape of moving cloth using a custom set of color markers printed on the surface of the cloth. The output is a sequence of triangle meshes with static co ..."
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Cited by 60 (1 self)
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Figure 1: We reconstruct a stationary sleeve using thousands of markers to estimate the geometry (texture added with bump mapping). We capture the shape of moving cloth using a custom set of color markers printed on the surface of the cloth. The output is a sequence of triangle meshes with static connectivity and with detail at the scale of individual markers in both smooth and folded regions. We compute markers ’ coordinates in space using correspondence across multiple synchronized video cameras. Correspondence is determined from color information in small neighborhoods and refined using a novel strain pruning process. Final correspondence does not require neighborhood information. We use a novel data driven holefilling technique to fill occluded regions. Our results include several challenging examples: a wrinkled shirt sleeve, a dancing pair of pants, and a rag tossed onto a cup. Finally, we demonstrate that cloth capture is reusable by animating a pair of pants using human motion capture data. 1
Fast proximity computation among deformable models using discrete Voronoi diagrams
 ACM TRANS. GRAPH. (PROC ACM SIGGRAPH
, 2006
"... We present novel algorithms to perform collision and distance queries among multiple deformable models in dynamic environments. These include interobject queries between different objects as well as intraobject queries. We describe a unified approach to compute these queries based on Nbody dist ..."
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Cited by 46 (9 self)
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We present novel algorithms to perform collision and distance queries among multiple deformable models in dynamic environments. These include interobject queries between different objects as well as intraobject queries. We describe a unified approach to compute these queries based on Nbody distance computation and use properties of the 2 nd order discrete Voronoi diagram to perform Nbody culling. Our algorithms involve no preprocessing and also work well on models with changing topologies. We can perform all proximity queries among complex deformable models consisting of thousands of triangles in a fraction of a second on a highend PC. Moreover, our Voronoibased culling algorithm can improve the performance of separation distance and penetration queries by an order of magnitude.
Dynamic simulation of articulated rigid bodies with contact and collision
 IEEE TVCG
, 2006
"... We propose a novel approach for dynamically simulating articulated rigid bodies undergoing frequent and unpredictable contact and collision. In order to leverage existing algorithms for nonconvex bodies, multiple collisions, large contact groups, stacking, etc., we use maximal rather than generaliz ..."
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Cited by 40 (5 self)
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We propose a novel approach for dynamically simulating articulated rigid bodies undergoing frequent and unpredictable contact and collision. In order to leverage existing algorithms for nonconvex bodies, multiple collisions, large contact groups, stacking, etc., we use maximal rather than generalized coordinates and take an impulse based approach that allows us to treat articulation, contact and collision in a unified manner. Traditional constraint handling methods are subject to drift, and we propose a novel prestabilization method that does not require tunable potentially stiff parameters as does Baumgarte stabilization. This differs from poststabilization in that we compute allowable trajectories before moving the rigid bodies to their new positions, instead of correcting them after the fact when it can be difficult to incorporate the effects of contact and collision. A poststabilization technique is used for momentum and angular momentum. Our approach works with any black box method for specifying valid joint constraints, and no special considerations are required for arbitrary closed loops or branching. Moreover, our implementation is linear both in the number of bodies and in the number of auxiliary contact and collision constraints, unlike many other methods that are linear in the number of bodies but not in the number of auxiliary constraints.
Interactive collision detection between deformable models using chromatic decomposition
 ACM Trans. Graph
, 2005
"... We present a novel algorithm for accurately detecting all contacts, including selfcollisions, between deformable models. We precompute a chromatic decomposition of a mesh into nonadjacent primitives using graph coloring algorithms. The chromatic decomposition enables us to check for collisions bet ..."
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Cited by 37 (6 self)
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We present a novel algorithm for accurately detecting all contacts, including selfcollisions, between deformable models. We precompute a chromatic decomposition of a mesh into nonadjacent primitives using graph coloring algorithms. The chromatic decomposition enables us to check for collisions between nonadjacent primitives using a lineartime culling algorithm. As a result, we achieve higher culling efficiency and significantly reduce the number of false positives. We use our algorithm to check for collisions among complex deformable models consisting of tens of thousands of triangles for cloth modeling and medical simulation. Our algorithm accurately computes all contacts at interactive rates. We observed up to an order of magnitude speedup over prior methods.
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 28 (8 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.
Virtual garments: A fully geometric approach for clothing design
 COMPUTER GRAPHICS FORUM (EUROGRAPHICS 2006)
, 2006
"... Modeling dressed characters is known as a very tedious process. It usually requires specifying 2D fabric patterns, positioning and assembling them in 3D, and then performing a physicallybased simulation. The latter accounts for gravity and collisions to compute the rest shape of the garment, with ..."
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Cited by 27 (2 self)
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Modeling dressed characters is known as a very tedious process. It usually requires specifying 2D fabric patterns, positioning and assembling them in 3D, and then performing a physicallybased simulation. The latter accounts for gravity and collisions to compute the rest shape of the garment, with the adequate folds and wrinkles. This paper presents a more intuitive way to design virtual clothing. We start with a 2D sketching system in which the user draws the contours and seamlines of the garment directly on a virtual mannequin. Our system then converts the sketch into an initial 3D surface using an existing method based on a precomputed distance field around the mannequin. The system then splits the created surface into different panels delimited by the seamlines. The generated panels are typically not developable. However, the panels of a realistic garment must be developable, since each panel must unfold into a 2D sewing pattern. Therefore our system automatically approximates each panel with a developable surface, while keeping them assembled along the seams. This process allows us to output the corresponding sewing patterns. The last step of our method computes a natural rest shape for the 3D garment, including the folds due to the
A DataDriven Approach for RealTime Clothes Simulation
 COMPUTER GRAPHICS FORUM
, 2005
"... A datadriven approach for the realtime processing of clothes, particularly suitable for simulating dresses worn by virtual characters, is proposed. It starts, prior to realtime simulation, by analyzing cloth behavior in relation to the underlying skeleton movement from a presimulated sequence of ..."
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Cited by 23 (1 self)
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A datadriven approach for the realtime processing of clothes, particularly suitable for simulating dresses worn by virtual characters, is proposed. It starts, prior to realtime simulation, by analyzing cloth behavior in relation to the underlying skeleton movement from a presimulated sequence of the cloth obtained using any highquality offline simulators. The idea is to use this analysis to find an optimal combination of physicsbased simulation and geometric approximation of the simulator; potentially colliding regions are defined on the cloth such that they will hold true for the skeleton movement that closely matches that of presimulated sequence. At runtime, using these analyses, our simulation process provides both visually pleasing results and performance, as long as the motion of the character remains sufficiently close to the original sequence used for the precomputation. The key contributions of this paper are (1) efficient collision handling that prunes out potentially colliding objects by using the offline simulation sequence as examples; (2) datadriven fixup process for the coarse mesh simulation that deduces the gross behavior of the cloth; and (3) geometric approximation of the fine mesh deformation, responsible for details in the shape of the cloth such as wrinkles.