We present an efficient algorithm for simulating contacts between deformable bodies with high-resolution surface geometry using dynamic deformation textures, which reformulate the 3D elastoplastic deformation and collision handling on a 2D parametric atlas to reduce the extremely high number of degrees of freedom in such a computationally demanding simulation. We perform proximity queries for deformable bodies using a two-stage algorithm directly on dynamic deformation textures, resulting in output-sensitive collision detection that is independent of the combinatorial complexity of the deforming meshes. We present a robust, parallelizable formulation for computing constraint forces using implicit methods that exploits the structure of the motion equations to achieve highly stable simulation, while taking large time steps with inhomogeneous materials. The dynamic deformation textures can also be used directly for real-time shading and can easily be implemented using SIMD architecture on commodity hardware. We show that our approach, complementing existing pioneering work, offers significant computational advantages on challenging contact scenarios in dynamic simulation of deformable bodies. 1.

Fast contact handling of soft articulated characters is a computationally challenging problem, in part due to complex interplay between skeletal and surface deformation. We present a fast, novel algorithm based on a layered representation for articulated bodies that enables physically-plausible simulation of animated characters with a high-resolution deformable skin in real time. Our algorithm gracefully captures the dynamic skeleton-skin interplay through a novel formulation of elastic deformation in the pose space of the skinned surface. The algorithm also overcomes the computational challenges by robustly decoupling skeleton and skin computations using careful approximations of Schur complements, and efficiently performing collision queries by exploiting the layered representation. With this approach, we can simultaneously handle large contact areas, produce rich surface deformations, and capture the collision response of a character’s skeleton.

This paper presents a fast method for determining an approximation of the local penetration information for intersecting polyhedral models. As opposed to most techniques, this algorithm requires no specific knowledge of the object’s geometry or topology, or any pre-processing computations. In order to achieve real-time performance even for complex, nonconvex models, we decouple the computation of the local penetration directions from the computation of the corresponding local penetration depths: for any pair of intersecting objects, we partition the penetrating zones into coherent regions, and we determine for each of these regions a local penetration direction. Then, for each of these regions, we estimate a local penetration depth in the previously computed penetration direction. This method has been implemented and tested on a 2.0 GHz Pentium PC with a NVIDIA GeForce FX 5900 graphics card with AGP 4 × and 768MB of RAM. The examples indicate that a meaningful local penetration information can be computed for complex models and challenging intersection scenarios within a few milliseconds. 1

This paper presents a modular algorithm for six-degree-of-freedom (6-DOF) haptic rendering. The algorithm is aimed to provide transparent manipulation of rigid models with a high polygon count. On the one hand, enabling a stable display is simplified by exploiting the concept of virtual coupling and employing passive implicit integration methods for the simulation of the virtual tool. On the other hand, transparency is enhanced by maximizing the update rate of the simulation of the virtual tool, and thereby the coupling impedance, and allowing for stable simulation with small mass values. The combination of a linearized contact model that frees the simulation from the computational bottleneck of collision detection, with penalty-based collision response well suited for fixed time-stepping, guarantees that the motion of the virtual tool is simulated at the same high rate as the synthesis of feedback force and torque. Moreover, sensation-preserving multiresolution collision detection ensures a fast update of the linearized contact model in complex contact scenarios, and a novel contact clustering technique alleviates possible instability problems induced by penalty-based collision response.

We present a new image-based method to process contacts between objects bounded by triangular surfaces. Unlike previous methods, it relies on image-based volume minimization, which eliminates complex geometrical computations and robustly handles deep intersections. The surfaces are rasterized in three orthogonal directions, and intersections are detected based on pixel depth and normal orientation. Per-pixel contact forces are computed and accumulated at the vertices. We show how to compute pressure forces which serve to minimize the intersection volume, as well as friction forces. No geometrical precomputation is required, which makes the method efficient for both deformable and rigid objects. We demonstrate it on rigid, skinned, and particle-based physical models with detailed surfaces in contacts at interactive frame rates. 1.

This paper decribes a general event-based approach to improve multimodal rendering of 6DOF (degree of freedom) contact between objects in interactive virtual object simulations. The contact events represent the different steps of two objects colliding with each other: (1) the state of free motion, (2) the impact event at the moment of collision (3) the friction state during the contact and (4) the detachment event at the end of the contact. The different events are used to improve the classical feedback by superimposing specific rendering techniques based on these events. First we propose a general method to generate these events based only on the objects ’ positions given by the simulation. Second, we describe a set of different types of multimodal feedback associated to the different events that we implemented in a complex virtual simulation dedicated to virtual assembly. For instance, we propose a visual rendering of impact, friction and detachment based on particle effects. We used the impact event to improve the 6DOF haptic rendering by superimposing a high frequency force pattern to the classical force feedback. We also implemented a realistic audio rendering using impact and friction sound on the corresponding events. All these first implementations can be easily extended with other event-based effects on various rigid body simulations thanks to our modular approach.

Abstract — Advanced, synthetic haptic virtual environments require textured virtual surfaces. We found that texturing smooth surfaces often reduces the system passivity margin of a haptic simulation. As a result, a smooth virtual surface that can be rendered in a passive manner may loose this property once textured. We propose that any texture algorithm is associated with a characteristic number that expresses the relative change in loop gain. We further found that a passive virtual interaction can have severe unwanted artifacts if the synthesized force field is not conservative. The energy characteristics of seven algorithms are analyzed. Finally a new texture synthesis algorithm, which operates by modulating a friction force during scanning, is shown to have several advantages over previous ones.

Hair designing is one of crucial components of the hair simulation tasks. The efficiency of hair modeling is very much determined by the interactivity and the ease-to-use the designing tools within an application. This paper presents a unified framework that uses the various key techniques developed for specific tasks in hair simulation and to realize the ultimate goal of ‘virtual hairdressing room ’ that is simple to use but quite effective for generating fast hairstyles. Successful attempts have been made to handle the different challenging issues involved in simulation of hair at interactive rates. Effort has been put in developing methodologies for hair shape modeling, hair dynamics and hair rendering. A user friendly interface controlled by a haptic device facilitates designer’s interactivity with the hairstyles. Furthermore, designer’s visualization is enhanced by using real time animation and interactive rendering. Animation is done using a modified Free Form Deformation (FFD) technique that has been effectively adapted to various hairstyles. Hair Rendering is performed using an efficient scattering based technique, displaying hair with its various optical effects.

Abstract. We present an efficient algorithm for haptic rendering of deformable bodies with highly detailed surface geometry using a fast contact handling algorithm. We exploit a layered deformable representation to augment the physically based deformation simulation with efficient collision detection, contact handling and interactive haptic force feedback. Keywords: Haptic Display, Collision Detection, Deformable Models. 1

One of the most salient haptic characteristics of objects is surface texture. Psychophysics studies have identified several key factors that affect perception of roughness during exploration of surface textures. Inspired by these recent findings, we develop the first force model for haptic display of interaction between two textured objects. We describe how our force model accounts for important elements identified by psychophysics studies. We then analyze and validate our model by comparing our simulation results against actual perceptual studies. We show that our model captures similar effects to those observed in the earlier experiments on roughness perception. 1