vriphys07
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Item A Real-time Implementation of the Dynamic Particle Coating Method on a GPU Architecture(The Eurographics Association, 2007) Sillam, Kevin; Evrard, Matthieu; Luciani, Annie; John Dingliana and Fabio GanovelliThis paper deals with a real-time implementation on graphic processor of the dynamic particle coating method (DPCM) first proposed by [HL02] and founded on a mass-interaction formalism. When this method was proposed, it was too much time-consuming to be inserted in an interactive application. This paper solves this major drawback. Our real-time implementation allows inserting this method in a real-time simulation chain composed of a haptic device, an upstream mass-interaction model that interacts with the user through this device and the new real-time implementation of the DPCM method to visualize this modelItem Constraint Sets for Topology-changing Finite Element Models(The Eurographics Association, 2007) Gissler, Marc; Becker, Markus; Teschner, Matthias; John Dingliana and Fabio GanovelliWe propose constraint sets as an efficient data structure for topology-changing deformable tetrahedral meshes. Using constraint sets, data structure updates in case of topology changes are simple and efficient. The consistency of the geometric representation is maintained and elasto-mechanical properties of the object are preserved. In combination with a Finite Element model for elasto-plastic objects and a geometric constraint approach, con- straint sets are applied to simulate the merging and breaking of conforming and non-conforming tetrahedral meshes. Experiments illustrate the efficiency of the data structure in interactive applications and its versatility.Item Occlusion-Based Snow Accumulation Simulation(The Eurographics Association, 2007) Foldes, David; Benes, Bedrich; John Dingliana and Fabio GanovelliWe present a fast technique for the simulation of accumulated snow. Our technique is based on two phenomena; local occlusion of small holes and ditches, and the global influence of a skylight. We use ambient occlusion to predict the shape and location of snow accumulation and direct illumination from the skylight to simulate the melting and sublimation of snow as dissipation. The snow is simulated as a 3D layer that is added to the input scene. Our technique is a fast approximation and does not aim to be used for small and local features within a simulation. A scene with over 500k triangles can be calculated in about seven minutes on a standard computer and the major part of the calculation runs on the GPU. Results of our algorithm should be used for large distance views.Item A Physically Based Deformation Model for Interactive Cartoon Animation(The Eurographics Association, 2007) Garcia, Marcos; Dingliana, John; O'Sullivan, Carol; John Dingliana and Fabio GanovelliWe present an approach for automatic cartoon-style motion dramatization suitable for interactive realtime animation. The system is built upon a physically based deformation model previously discussed in [GMPR06] and achieves squash-and-stretch cartoon deformation relevant to the current object velocity by controlling the deformations in the physically based model. As an improvement over previous similar approaches, which largely provide geometrical solutions to the problem, our modified physics-based deformation approach handles more general cases.Item Virtual Adhesive: a Way to Handle Sticky Collisions in Surgical and Biological Simulators(The Eurographics Association, 2007) Carra, Alexandre; Martiel, Jean-Louis; Promayon, Emmanuel; John Dingliana and Fabio GanovelliA variety of methods have been proposed to efficiently process collisions between deformable objects. The method presented in this paper allows to model sticky states between deformable objects with triangulated surfaces. In contrast to an often used approach that consists of generating forces which eventually separate colliding objects, our method is based on the creation of an adhesive virtual object (virtual adhesive). This virtual adhesive is composed by "clones" of all particles locally in collision. Particle clones are used to gather forces on the virtual adhesive, which behaves like a rigid body. The resulting displacement of the virtual adhesive is used in turn to constrain the particles displacement: particles stick to their clone. As a result, no further interpenetration is possible and a sticky state is obtained in the considered zone. Moreover, the method correctly resolves contacts without introducing additional energy in the system. Results are presented through several simulations.Item Refraction of Water Surface Intersecting Objects in Interactive Environments(The Eurographics Association, 2007) Cords, Hilko; John Dingliana and Fabio GanovelliThis paper presents a rapid method to render dynamic water surfaces with penetrating obstacles in real-time. Taking the surface boundary into account, our method allows the rendering of single reflections and single refractions of objects even intersecting the water surface, including a physically approximative perspective refraction mapping. Thereby, water surfaces are represented as 2.5D height fields and obstacles as polygonal objects. In principle, we determine approximating virtual reflection and refraction eye coordinates. With respect to the water surface, the reflected and refracted objects and parts of objects are projected onto the surface from separate, virtual eye coordinates. Since we are using per-pixel reflection and refraction mapping, our multi-pass, image-based technique is suitable for GPU-based implementations. Moreover, we demonstrate the interactive application of the method for height field based data sets extracted from interactive 3D Smoothed Particle Hydrodynamics (SPH) simulations in real-time. Thereby, the presented approach achieves high frame rates and plausible results.Item Medial Surface-Based Real Time Simulation of Elastic Objects(The Eurographics Association, 2007) Pfaff, Matthias; Wuethrich, Charles Albert; John Dingliana and Fabio GanovelliThis paper presents a method for the real time simulation of the dynamical behaviour of elastic objects which bases on the medial surface. From a surface based 3D model, the medial surface is generated automatically without any intervention by the user. The medial surface is used as a skeleton for movement. It is connected to the surface of the model through a mass-spring system based on surface bone points that allows the simulation of surface movement. A new technique for constraining movement within the mass-spring system is used to stabilize the physical shape of the object. Different parameter settings allow the simulation of a variety of different elastic materials. Joints can be applied and simulated by parting the skeleton into different joint sections.Item Hardware Accelerated Broad Phase Collision Detection for Realtime Simulations(The Eurographics Association, 2007) Woulfe, Muiris; Dingliana, John; Manzke, Michael; John Dingliana and Fabio GanovelliBroad phase collision detection is a vital task in most interactive simulations, but it remains computationally expensive and is frequently an impediment to efficient implementation of realtime graphics applications. To over- come this hurdle, we propose a novel microarchitecture for performing broad phase collision detection using Axis-Aligned Bounding Boxes (AABBs), which exploits the parallelism available in the algorithms. We have im- plemented our microarchitecture on a Field-Programmable Gate Array (FPGA) and our results show that this im- plementation is capable of achieving an acceleration of up to 1.5× over the broad phase component of the SOLID collision detection library, when considering the communication overhead between the CPU and the FPGA. Our results further indicate that significantly higher accelerations are achievable using a more sophisticated FPGA or by implementing our microarchitecture on an Application-Specific Integrated Circuit (ASIC).Item A Fast and Compact Solver for the Shallow Water Equations(The Eurographics Association, 2007) Lee, Richard; O'Sullivan, Carol; John Dingliana and Fabio GanovelliThis paper presents a fast and simple method for solving the shallow water equations. The water velocity and height variables are collocated on a uniform grid and a novel, unified scheme is used to advect all quantities together. Furthermore, we treat the fluid as weakly compressible to avoid solving a pressure Poisson equation. We sacrifice accuracy and unconditional stability for speed, but we show that our algorithm is sufficiently stable and fast enough for real-time applications.Item Real-Time Erosion Using Shallow Water Simulation(The Eurographics Association, 2007) Benes, Bedrich; John Dingliana and Fabio GanovelliWe present a new real-time hydraulic erosion simulation for Computer Graphics. In our system water runs over the surface and disintegrates the underlying layer of soil. The grit is simulated as a fluid with higher viscosity and moves on the ground of the water pool. When water evaporates, or the dissolved soil exceeds a critical level, the dissolved matter is deposited back on the ground for accumulation to occur. The grit motion as well as the water simulation are calculated by the shallow water simulation that is a 2D simplification of Navier-Stokes equations. This simulation has proven to be useful in many Computer Graphics applications because of the speed of calculation and the visual plausibility of the results. Our experiments show that the shallow water-based erosion is suitable for real-time simulation of a wide variety of phenomena including river and lake formation due to rain and evaporation, erosion of surfaces affected by a sudden splash of high level of water, mountain erosion, etc. The speed of simulation makes the algorithm suitable for real-time surface modeling and editing.