Lateral Touch and Frictional Vibrations of Human Fingerprints

In this report, we experimentally show that human fingerprints play a significant role in the lateral touch vibratory mechanisms and that direction of movement results in differ-ent dynamic strains on the pulp. Sources that generate sound at the interface are first empiri-cally identified and a spherical model of the index finger is proposed to forecast the radiated fields. Then, haptic sounds are recorded using a miniature microphone placed in the near field. Results are compared with vibrometric measurements carried out in quite similar conditions to assess of the results relevance. Results show that fingerprints can?t be neglected in the tri-bologic interaction. Finally, this research provide a useful information for tactile displays de-signers and offers future investigations perspectives in many research fields linked with the haptic science

Asynchronous Interactive Physical Simulation

This document introduces a multi-agent framework for real-time physical simulation. Unlike classical physical simulators, no shared discrete time-line is imposed to simulated objects. Each simulated object is an autonomous agent that can maintain its simulation state, and possibly modify its behavior by checking its environment. Decision schemes are proposed that enable objects to locally adapt their computation time, in order to maintain approximate global synchronization. Results and measures are presented, especially regarding time management and simulation synchronization in regard of classical simulation methods. Examples are shown, outlining some of the practical advantages such a framework provides

Generalized God-Objects: a Paradigm for Interacting with Physically-Based Virtual World

International audienceIn this paper, we show a method to interact with physically-based environments in a way which guarantee their integrity whatever the mechanical properties of the virtual interaction tool and the control device. It consists in an extension of the god-object concept. The interaction tools are modeled as physical bodies which tend to reach, if possible, the position maintained by the user. Their behavior is computed via the dynamic laws of motion by the simulation engine, as the other bodies in the scene. The cases of articulated rigid bodies and deformable bodies are studied. This mechanism also provides a unified framework which allows the control of virtual objects via devices providing force feedback or not. Finally, some applications including virtual surgery are shown to illustrate the effectiveness of the approach

Adaptive resolution of 1D mechanical B-spline

International audienceThis article presents an adaptive approach to B-spline curve physical simulation. We combine geometric refinement and coarsening techniques with an appropriate continuous mechanical model. We thus deal with the (temporal and geometric) continuity issues implied when mechanical adaptive resolution is used. To achieve real-time local adaptation of spline curves, some criteria and optimizations are shown. Among application examples, real-time knot tying is presented, and curve cutting is also pointed out as a nice sideeffect of the adaptive resolution animation framework

RubberEdge: Reducing Clutching by Combining Position and Rate Control with Elastic Feedback

Position control devices enable precise selection, but significant clutching degrades performance. Clutching can be reduced with high control-display gain or pointer acceleration, but there are human and device limits. Elastic rate control eliminates clutching completely, but can make precise selection difficult. We show that hybrid position-rate control can outperform position control by 20% when there is significant clutching, even when using pointer acceleration. Unlike previous work, our RubberEdge technique eliminates trajectory and velocity discontinuities. We derive predictive models for position control with clutching and hybrid control, and present a prototype RubberEdge position-rate control device including initial user feedback.Comment: 10 page

Indexing and retrieval VRML models

International audienceIn this paper we present a three-dimensional model retrieval system. A three-dimensional model is described by two invariant descriptors: a shape index and a histogram of distances between meshes. This work focuses on extracting invariant descriptors that well represent a three-dimensional model, and on combining theses descriptors in order to get a better retrieval performance. An experimental evaluation demonstrates the good performance of the approach

Smooth constraints for spline variational modeling

International audienceThis article introduces a new class of constraints for spline variational modeling, which allows more flexible user specification, as a constrained point can `slide' along a spline curve. Such constraints can, for example, be used to preserve correct parameterization of the spline curve. The spline surface case is also studied. Efficient numerical schemes are discussed for real-time solving, as well as interactive visualization during the energy minimization process. Examples are shown, and numerical results discussed

Fast Polygonization of Implicit Surfaces

ABSTRACT Our work is centered on the use of implicit surfaces in interactive applications (at least 10 frames per sec) running on high-end consumer architecture (modeling, simulation, deformable body animation, games). We focus on the Marching Cubes algorithm that we tried to implement in an optimized way. We restrict our work to blended iso-surfaces generated by skeletons, since this kind of implicit surfaces is the most handy to use for animations. Our implementation optimizations deal with the following features: simplifying the field function, accelerating its evaluation for each point (voxel-based technique), generating automatically the triangles for any case of the Marching Cubes. Another point we have considered concerns tesselation ambiguities often resulting in holes appearing in the surface. We have coded a library which is very easy to use and can be downloaded freely. All these optimizations allow us to sample implicit surfaces composed of 200 points in 45 ms on a 450 MHz Pentium II Xeon

An Intestinal Surgery Simulator: Real-Time Collision Processing and Visualization

International audienceThis research work is aimed towards the development of a VR-based trainer for colon cancer removal. It enables the surgeons to interactively view and manipulate the concerned virtual organs as during a real surgery. First, we present a method for animating the small intestine and the mesentery (the tissue that connects it to the main vessels) in real-time, thus enabling user-interaction through virtual surgical tools during the simulation. We present a stochastic approach for fast collision detection in highly deformable, self-colliding objects. A simple and efficient response to collisions is also introduced in order to reduce the overall animation complexity. Secondly, we describe a new method based on generalized cylinders for fast rendering of the intestine. An efficient curvature detection method, along with an adaptive sampling algorithm is presented. This approach, while providing improved tessellation without the classical self-intersection problem, also allows for high-performance rendering, thanks to the new 3D skinning feature available in recent GPUs. The rendering algorithm is also designed to ensure a guaranteed frame rate. Finally, we present the quantitative results of the simulations and describe the qualitative feedback obtained from the surgeons

Implicit Representations of the Human Intestines for Surgery Simulation

International audienceIn this paper, we propose a modeling of the intestines by implicit surfaces for abdominal surgery simulation. The difficulty of such a simulation comes from the animation of the intestines. As a matter of fact, the intestines are a very long tube that is not isotropically elastic, and that bends over itself at various spots, creating multiple self-contacts. We use a multiple component model for the intestines: The first component is a mechanical model of their axis; the second component is a specific sphere-based model to manage collisions and self-collisions; and the third component is a skinning model to define their volume. This paper focuses on the better representation for skinning the intestines. We compare two implicit models: Surfaces defined by point-skeletons and convolution surfaces. A direct application of this simulation is the training of a typical surgical gesture to move apart the intestines in order to reach certain areas of the abdomen