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41
BDTree: OutputSensitive Collision Detection for Reduced Deformable Models
 ACM Transactions on Graphics (SIGGRAPH
, 2004
"... We introduce the Bounded Deformation Tree, or BDTree, which can perform collision detection with reduced deformable models at costs comparable to collision detection with rigid objects. Reduced deformable models represent complex deformations as linear superpositions of arbitrary displacement field ..."
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Cited by 98 (11 self)
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We introduce the Bounded Deformation Tree, or BDTree, which can perform collision detection with reduced deformable models at costs comparable to collision detection with rigid objects. Reduced deformable models represent complex deformations as linear superpositions of arbitrary displacement fields, and are used in a variety of applications of interactive computer graphics. The BDTree is a bounding sphere hierarchy for outputsensitive collision detection with such models. Its bounding spheres can be updated after deformation in any order, and at a cost independent of the geometric complexity of the model; in fact the cost can be as low as one multiplication and addition per tested sphere, and at most linear in the number of reduced deformation coordinates. We show that the BDTree is also extremely simple to implement, and performs well in practice for a variety of realtime and complex offline deformable simulation examples.
Supplement for realtime soft shadows in dynamic scenes using spherical harmonic exponentiation
 Microsoft Corporation. available on the SIGGRAPH 2006 Conference DVD
, 2006
"... Previous methods for soft shadows numerically integrate over many light directions at each receiver point, testing blocker visibility in each direction. We introduce a method for realtime soft shadows in dynamic scenes illuminated by large, lowfrequency light sources where such integration is impr ..."
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Cited by 43 (8 self)
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Previous methods for soft shadows numerically integrate over many light directions at each receiver point, testing blocker visibility in each direction. We introduce a method for realtime soft shadows in dynamic scenes illuminated by large, lowfrequency light sources where such integration is impractical. Our method operates on vectors representing lowfrequency visibility of blockers in the spherical harmonic basis. Blocking geometry is modeled as a set of spheres; relatively few spheres capture the lowfrequency blocking effect of complicated geometry. At each receiver point, we compute the product of visibility vectors for these blocker spheres as seen from the point. Instead of computing an expensive SH product per blocker as in previous work, we perform inexpensive vector sums to accumulate the log of blocker visibility. SH exponentiation then yields the product visibility vector over all blockers. We show how the SH exponentiation required can be approximated accurately and efficiently for loworder SH, accelerating previous CPUbased methods by a factor of 10 or more, depending on blocker complexity, and allowing realtime GPU implementation.
Ray Tracing Dynamic Scenes using Selective Restructuring
 EUROGRAPHICS SYMPOSIUM ON RENDERING (2007) JAN KAUTZ AND SUMANTA PATTANAIK (EDITORS)
, 2007
"... We present a novel algorithm to selectively restructure bounding volume hierarchies (BVHs) for ray tracing dynamic scenes. We derive two new metrics to evaluate the culling efficiency and restructuring benefit of any BVH. Based on these metrics, we perform selective restructuring operations that eff ..."
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Cited by 18 (5 self)
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We present a novel algorithm to selectively restructure bounding volume hierarchies (BVHs) for ray tracing dynamic scenes. We derive two new metrics to evaluate the culling efficiency and restructuring benefit of any BVH. Based on these metrics, we perform selective restructuring operations that efficiently reconstruct small portions of a BVH instead of the entire BVH. Our approach is general and applicable to complex and dynamic scenes, including topological changes. We use the selective restructuring algorithm to improve the performance of ray tracing dynamic scenes that consist of hundreds of thousands of triangles. In our benchmarks, we observe up to an order of magnitude improvement over prior BVHbased ray tracing algorithms.
Gross / Visibility Transition Planning for Dynamic Camera Control HSU D.: A greedy strategy for tracking a locally predictable target among obstacles
 In Proc. IEEE Int. Conf. on Robotics & Automation (2006
"... We present a realtime camera control system that uses a global planning algorithm to compute large, occlusion free camera paths through complex environments. The algorithm incorporates the visibility of a focus point into the search strategy, so that a path is chosen along which the focus target wi ..."
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Cited by 17 (1 self)
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We present a realtime camera control system that uses a global planning algorithm to compute large, occlusion free camera paths through complex environments. The algorithm incorporates the visibility of a focus point into the search strategy, so that a path is chosen along which the focus target will be in view. The efficiency of our algorithm comes from a visibilityaware roadmap data structure that permits the precomputation of a coarse representation of all collisionfree paths through an environment, together with an estimate of the pairwise visibility between all portions of the scene. Our runtime system executes a path planning algorithm using the precomputed roadmap values to find a coarse path, and then refines the path using a sequence of occlusion maps computed onthefly. An iterative smoothing algorithm, together with a physicallybased camera model, ensures that the path followed by the camera is smooth in both space and time. Our global planning strategy on the visibilityaware roadmap enables largescale camera transitions as well as a local thirdperson camera module that follows a player and avoids obstructed viewpoints. The data structure itself adapts at runtime to dynamic occluders that move in an
Fast collision detection for skeletally deformable models
 In: Proceedings of eurographics; 2005
"... We present a new method of collision detection for models deformed by linear blend skinning. The linear blend skinning (also known as skeletonsubspace deformation, vertexblending, or enveloping) is a popular method to animate believable organic models. We consider an exact collision detection base ..."
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Cited by 15 (3 self)
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We present a new method of collision detection for models deformed by linear blend skinning. The linear blend skinning (also known as skeletonsubspace deformation, vertexblending, or enveloping) is a popular method to animate believable organic models. We consider an exact collision detection based on a hierarchy of bounding spheres. The main problem with this approach is the update of bounding volumes – they must follow the current deformation of the model. We introduce a new fast method to refit the bounding spheres, which can be executed on spheres in any order. Thanks to this ondemand refitting operation we obtain a collision detection algorithm with speed comparable to the standard rigid body collision detection. The algorithm was tested on a variety of practical situations, including an animated crowd. According to these experiments, the proposed approach is considerably faster than the previous method.
Fast continuous collision detection using deforming nonpenetration filters
 SIGGRAPH
"... Figure 1: Benchmark Lion: In this simulation, a spherical ball falls on top of a Chinese statue of a lion and the lion gradually breaks into a high number of colliding pieces. This model has 805K vertices and 1.6M triangles. In this scene with changing topologies, our novel collision detection algor ..."
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Cited by 14 (1 self)
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Figure 1: Benchmark Lion: In this simulation, a spherical ball falls on top of a Chinese statue of a lion and the lion gradually breaks into a high number of colliding pieces. This model has 805K vertices and 1.6M triangles. In this scene with changing topologies, our novel collision detection algorithm based on a deforming filter increases the culling efficiency and reduces the number of elementary tests by 10x when compared to prior methods and improves the performance of the CCD algorithm by 4.1x. We present a novel culling algorithm that uses deforming nonpenetration filters to improve the performance of continuous collision detection (CCD) algorithms. The underlying idea is to use a simple and effective filter that reduces both the number of false positives and the elementary tests between the primitives. This filter is derived from the coplanarity condition and can be easily combined with other methods used to accelerate CCD. We have implemented the algorithm and tested its performance on many nonrigid simulations. In practice, we can reduce the number of false positives significantly and improve the overall performance of CCD algorithms by 1.5 − 8.2x. 1
Domain connected graph : the skeleton of a closed 3D shape for animation. The Visual Computer 22
, 2006
"... Abstract In previous research, three main approaches have been employed to solve the skeleton extraction problem: Medial axis transform (MAT), generalized potential field and decomposition based methods. These three approaches have been formulated using three different concepts, namely surface varia ..."
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Cited by 11 (0 self)
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Abstract In previous research, three main approaches have been employed to solve the skeleton extraction problem: Medial axis transform (MAT), generalized potential field and decomposition based methods. These three approaches have been formulated using three different concepts, namely surface variation, inside energy distribution, and the connectivity of parts. By combining the above mentioned concepts, this paper creates a concise structure to represent the control skeleton of an arbitrary object. First, an algorithm is proposed to detect the end, connection and joint points of an arbitrary 3D object. These three points comprise the skeleton, and are the most important to consider when describing it. In order to maintain the stability of the point extraction algorithm, a prongfeature detection technique and a level isosurfaces function based on repulsive force field was employed. A neighborhood relationship inherited from the surface able to describe the connection relationship of these positions was then defined. Based on this relationship, the skeleton was finally constructed and named Domain Connected Graph (DCG). The DCG not only preserves the topology information of a 3D object, but is also less sensitive than MAT to the perturbation of shapes. Moreover, from the results of complicated 3D models, consisting
Collision Prediction Using MKtrees
 Proc. CEIG
, 2004
"... In this paper, the collision prediction between polyhedra under screw motions and a static scene using a new K dimensional tree data structure (Multiresolution Kdtree, MKtree) is introduced. In a complex scene containing a high number of individual objects, the MKtree represents a hierarchical subdi ..."
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Cited by 7 (0 self)
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In this paper, the collision prediction between polyhedra under screw motions and a static scene using a new K dimensional tree data structure (Multiresolution Kdtree, MKtree) is introduced. In a complex scene containing a high number of individual objects, the MKtree represents a hierarchical subdivision of the scene objects that guarantees a small space overlap between node regions. The proposed MKtree data structure succeeds in performing simultaneously space and scene subdivision. MKtrees are useful for broad phase collision and proximity detection tests and for timecritical rendering in large environments requiring external memory storage. The paper proposes an efficient broad phase collision prediction algorithm. Examples in ship design applications are presented and discussed..
Medial Spheres for Shape Approximation
"... Abstract We study the problem of approximating a solid with a union of overlapping spheres. We introduce a method based on medial spheres which, when compared to a stateoftheart approach, offers more than an order of magnitude speedup and achieves a tighter volumetric approximation of the origina ..."
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Cited by 6 (0 self)
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Abstract We study the problem of approximating a solid with a union of overlapping spheres. We introduce a method based on medial spheres which, when compared to a stateoftheart approach, offers more than an order of magnitude speedup and achieves a tighter volumetric approximation of the original mesh, while using fewer spheres. The spheres generated by our method are internal to the object, which permits an exact error analysis and comparison with other sphere approximations. We demonstrate that a tight bounding volume hierarchy of our set of spheres may be constructed using rectangleswept spheres as bounding volumes. Further, once our spheres are dilated, we show that this hierarchy generally offers superior performance in approximate separation distance tests. 1
MCCD: MultiCore Collision Detection between Deformable Models using FrontBased Decomposition
"... We present a novel parallel algorithm for fast continuous collision detection (CCD) between deformable models using multicore processors. We use a hierarchical representation to accelerate these queries and present an incremental algorithm that exploits temporal coherence between successive frames. ..."
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Cited by 6 (2 self)
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We present a novel parallel algorithm for fast continuous collision detection (CCD) between deformable models using multicore processors. We use a hierarchical representation to accelerate these queries and present an incremental algorithm that exploits temporal coherence between successive frames. Our formulation distributes the computation among multiple cores by using finegrained frontbased decomposition. We also present efficient techniques to reduce the number of elementary tests and analyze the scalability of our approach. We have implemented the parallel algorithm on 8 core and 16 core PCs, and observe up to 7X and 13X speedups respectively, on complex benchmarks.