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19
Volume contact constraints at arbitrary resolution
- ACM TRANS. GRAPH
, 2010
"... We introduce a new method for simulating frictional contact between volumetric objects using interpenetration volume constraints. When applied to complex geometries, our formulation results in dramatically simpler systems of equations than those of traditional mesh contact models. Contact between h ..."
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Cited by 24 (8 self)
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We introduce a new method for simulating frictional contact between volumetric objects using interpenetration volume constraints. When applied to complex geometries, our formulation results in dramatically simpler systems of equations than those of traditional mesh contact models. Contact between highly detailed meshes can be simplified to a single unilateral constraint equation, or accurately processed at arbitrary geometry-independent resolution with simultaneous sticking and sliding across contact patches. We exploit fast GPU methods for computing layered depth images, which provides us with the intersection volumes and gradients necessary to formulate the contact equations as linear complementarity problems. Straightforward and popular numerical methods, such as projected Gauss-Seidel, can be used to solve the system. We demonstrate our method in a number of scenarios and present results involving both rigid and deformable objects at interactive rates.
K.: Frame-based elastic models
- ACM Trans. Graph
, 2011
"... We present a new type of deformable model which combines the realism of physically based continuum mechanics models and the usability of framebased skinning methods. The degrees of freedom are coordinate frames. In contrast with traditional skinning, frame positions are not scripted but move in reac ..."
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Cited by 18 (6 self)
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We present a new type of deformable model which combines the realism of physically based continuum mechanics models and the usability of framebased skinning methods. The degrees of freedom are coordinate frames. In contrast with traditional skinning, frame positions are not scripted but move in reaction to internal body forces. The displacement field is smoothly interpolated using dual quaternion blending. The deformation gradient and its derivatives are computed at each sample point of a deformed object and used in the equations of Lagrangian mechanics to achieve physical realism. This allows easy and very intuitive definition of the degrees of freedom of the deformable object. The meshless discretization allows on-the-fly insertion of frames to create local deformations where needed. We formulate the dynamics of these models in detail and describe some pre-computations that can be used for speed. We show that our method is effective for behaviors ranging from simple unimodal deformations to complex realistic deformations comparable with Finite Element simulations. To encourage its use, the software will be freely available in the simulation platform SOFA.
Approximate boolean operations on large polyhedral solids with partial mesh reconstruction
- IEEE Transactions on Visualization and Computer Graphics
"... Abstract—We present a new approach to compute the approx-imate Boolean operations of two freeform polygonal mesh solids efficiently with the help of Layered Depth Images (LDI). After applying the LDI sampling based membership classification, the most challenging part, a trimmed adaptive contouring a ..."
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Cited by 8 (1 self)
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Abstract—We present a new approach to compute the approx-imate Boolean operations of two freeform polygonal mesh solids efficiently with the help of Layered Depth Images (LDI). After applying the LDI sampling based membership classification, the most challenging part, a trimmed adaptive contouring algorithm, is developed to reconstruct the mesh surface from the LDI samples near the intersected regions and stitch it to the boundary of the retained surfaces. Our method of approximate Boolean operations holds the advantage of numerical robustness as the approach uses volumetric representation. However, unlike other methods based on volumetric representation, we do not damage the facets in non-intersected regions, thus preserving geometric details much better and speeding up the computation as well. We show that the proposed method can successfully compute the Boolean operations of freeform solids with a massive number of polygons in a few seconds. Index Terms—Boolean operations, freeform solids, robust, approximation, Layered Depth Images. I.
INTERACTIVE DYNAMIC SIMULATOR FOR MULTIBODY SYSTEMS
, 2013
"... We propose an interactive dynamic simulator for humanoid robots using constraint-based methods for computing interaction forces with friction. This simulator is a part of a general framework for prototyping called AMELIF and is a successful integration of physical models. We focus on optimizing the ..."
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Cited by 5 (1 self)
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We propose an interactive dynamic simulator for humanoid robots using constraint-based methods for computing interaction forces with friction. This simulator is a part of a general framework for prototyping called AMELIF and is a successful integration of physical models. We focus on optimizing the computation of the dynamics to obtain real-time simulations allowing multimodal interactivity. Our simulator has been validated in two ways: ¯rst by comparing real sensors ' measures and simulated values, then through di®erent scenarios of complex manipulation tasks on the HRP-2 humanoid robot, bringing new insights to interactive robotics.
Interference-Aware Geometric Modeling
"... Figure 1: Interference-aware modeling greatly simplifies many complicated modeling tasks. We interactively fit the ogre with a shirt made for a human. We use our ability to fix existing intersections in a mesh and then “shrink-wrap ” the shirt on the ogre, ensuring a perfect fit. While often a requi ..."
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Cited by 4 (1 self)
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Figure 1: Interference-aware modeling greatly simplifies many complicated modeling tasks. We interactively fit the ogre with a shirt made for a human. We use our ability to fix existing intersections in a mesh and then “shrink-wrap ” the shirt on the ogre, ensuring a perfect fit. While often a requirement for geometric models, there has been little research in resolving the interaction of deforming surfaces during real-time modeling sessions. To address this important topic, we introduce an interference algorithm specifically designed for the domain of geometric modeling. This algorithm is general, easily working within existing modeling paradigms to maintain their important properties. Our algorithm is fast, and is able to maintain interactive rates on complex deforming meshes of over 75K faces, while robustly removing intersections. Lastly, our method is controllable, allowing fine-tuning to meet the specific needs of the user. This includes support for minimum separation between surfaces and control over the relative rigidity of interacting objects. Links: DL PDF 1
Whole-Body Pregnant Woman Modeling By Digital Geometry Processing With Detailed Uterofetal Unit Based on Medical Images
"... Abstract—Anatomical models of pregnant women are used in several applications, such as numerical dosimetry, to assess the potential effects of electromagnetic fields on biological tissues, or medical simulation. Recent advances in medical imaging have enabled the generation of realistic and detailed ..."
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Cited by 3 (2 self)
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Abstract—Anatomical models of pregnant women are used in several applications, such as numerical dosimetry, to assess the potential effects of electromagnetic fields on biological tissues, or medical simulation. Recent advances in medical imaging have enabled the generation of realistic and detailed models of human beings. The construction of pregnant woman models remains a complex task, since it is not possible to acquire whole-body images. Only few models have been developed up to now, and they all present some limitations regarding the representation of anatomical variability of the fetus shape and position over the entire gestation. This paper describes a complete methodology that intends to automate each step of the construction of pregnant women models. The proposed approach relies on the segmentation of 3-D ultrasonic and 3-D magnetic resonance imaging (MRI) data, and on dedicated computer graphics tools. The lack of complete anatomical information for the mother in image data is compensated, in an original way, by merging the available information with a synthetic woman model, deformed to match the image-based information. A set of models anatomically validated by clinical experts is presented. They include detailed information on uterofetal units and cover different gestational stages with various fetal positions. Index Terms—Anatomical modeling, computer graphics, fetus, medical imaging, mesh generation and deformation, MRI,
Air meshes for robust collision handling
- ACM Trans. Graph
, 2015
"... Figure 1: A dancer with a multi-layered skirt. Our method robustly simulates the complex interaction of the layers and is able to smoothly recover from any entangled state. We propose a new method for both collision detection and collision response geared towards handling complex deformable objects ..."
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Cited by 1 (0 self)
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Figure 1: A dancer with a multi-layered skirt. Our method robustly simulates the complex interaction of the layers and is able to smoothly recover from any entangled state. We propose a new method for both collision detection and collision response geared towards handling complex deformable objects in close contact. Our method does not miss collision events between time steps and solves the challenging problem of untangling auto-matically and robustly. It is conceptually simple and straight for-ward to parallelize due to the regularity of the algorithm. The main idea is to tessellate the air between objects once before the simulation and by considering one unilateral constraint per element that prevents its inversion during the simulation. If large relative ro-tations and translations are present in the simulation, an additional dynamic mesh optimization step is needed to prevent mesh lock-ing. This step is fast in 2D and allows the simulation of arbitrary scenes. Because mesh optimization is expensive in 3D, however, the method is best suited for the subclass of 3D scenarios in which relative motions are limited. This subclass contains two important problems, namely the simulation of multi-layered clothing and tis-sue on animated characters.
Grenoble Universities
, 2009
"... In this paper we introduce a new approach for the embedding of linear elastic deformable models. Our technique results in significant improvements in the efficient physically based simulation of highly detailed objects. First, our embedding takes into account topological details, that is, disconnect ..."
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In this paper we introduce a new approach for the embedding of linear elastic deformable models. Our technique results in significant improvements in the efficient physically based simulation of highly detailed objects. First, our embedding takes into account topological details, that is, disconnected parts that fall into the same coarse element are simulated independently. Second, we account for the varying material properties by computing stiffness and interpolation functions for coarse elements which accurately approximate the behaviour of the embedded material. Finally, we also take into account empty space in the coarse embeddings, which provides a better simulation of the boundary. The result is a straightforward approach to simulating complex deformable models with the ease and speed associated with a coarse regular embedding, and with a quality of detail that would only be possible at much finer resolution.
Interactive Physics Simulations
, 2010
"... Abstract. Today, it is possible to associate multiple CPUs and multiple GPUs in a single shared memory architecture. Using these resources efficiently in a seamless way is a challenging issue. In this paper, we propose a parallelization scheme for dynamically balancing work load between multiple CPU ..."
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Abstract. Today, it is possible to associate multiple CPUs and multiple GPUs in a single shared memory architecture. Using these resources efficiently in a seamless way is a challenging issue. In this paper, we propose a parallelization scheme for dynamically balancing work load between multiple CPUs and GPUs. Most tasks have a CPU and GPU implementation, so they can be executed on any processing unit. We rely on a two level scheduling associating a traditional task graph partitioning and a work stealing guided by processor affinity and heterogeneity. These criteria are intended to limit inefficient task migrations between GPUs, the cost of memory transfers being high, and to favor mapping small tasks on CPUs and large ones on GPUs to take advantage of heterogeneity. This scheme has been implemented to support the SOFA physics simulation engine. Experiments show that we can reach speedups of 22 with 4 GPUs and 29 with 4 CPU cores and 4 GPUs. CPUs unload GPUs from small tasks making these GPUs more efficient, leading to a “cooperative speedup ” greater than the sum of the speedups separatly obtained on 4 GPUs and 4 CPUs. 1
