Overall Objectives
Scientific Foundations
Application Domains
New Results
Contracts and Grants with Industry
Other Grants and Activities

Section: New Results

Animating nature

Participants : Sébastien Barbier, Eric Bruneton, Marie-Paule Cani, Mathieu Coquerelle, Julien Diener, Estelle Duveau, Florent Falipou, François Faure, Everton Hermann, Matthieu Nesme, Fabrice Neyret, Olivier Palombi, Cécile Picard, Lionel Reveret, Maxime Tournier, Xiaomao Wu, Qizhi Yu.

Highly colliding deformable bodies

Participants : Sébastien Barbier, Florent Falipou, François Faure, Everton Hermann.

We address the question of simulating highly deformable objects. We have focused on the collision detection and response between highly deformable bodies, where precomputed distance maps can not be used, and published two novel methods. The first, illustrated in Figure  8 one replaces a three-dimensional distance computation by a one-dimensional search along a ray, accelerated using an octree structure  [19] .

Figure 8. Simulation of highly deformable bodies in contact using our octree-based method. Left: initial state, center: proximity response, right: ray-trace response.

The second method  [17] , illustrated in Figure  9 , replaces distance computations with intersection volume computations. A novel GPU-based method computes the intersection volume between objects, as well as its derivatives with respect to the surface vertices. This allows the efficient implementation of penalty forces.

Figure 9. Simulation of highly deformable bodies in contact using our GPU-based method.

Robust finite elements for deformable solids

Participants : François Faure, Matthieu Nesme.

Figure 10. Snapshot of an interactive surgery simulation.

Matthieu Nesme has defended his Ph.D.  [4] on robust finite element modeling for surgery simulation, in collaboration with laboratory TIMC. Its purpose is to develop new models of finite elements for the interactive physically-based animation of human tissue. His regular grid based FEM approach allows the easy modeling and interactive simulation of complex scenes based on medical images, as illustrated in Figure  10 . He is now a post-doctoral student at University McGill, Montreal, Canada.

Sound synthesis

Participants : François Faure, Cécile Picard.

Figure 11. Textures can be used for audio synthesis.

Cécile Picard, a PhD. student, was previously in Sophia-Antipolis tutored by Nicolas Tsingos and George Drettakis. She has joined us in July, since Nicolas moved to Dolby Labs in California, and will be co-tutored by François Faure and George Drettakis during the rest of her thesis. We published a method for sound synthesis in game engines  [22] , where height profiles are extracted from textures and used as input to the sound generation module, as illustrated in Figure  11 .

Real-time animation of liquids and river surfaces

Participants : Eric Bruneton, Marie-Paule Cani, Mathieu Coquerelle, Fabrice Neyret, Qizhi Yu.

Figure 12. Our river animation and reconstruction model handles the real-time dynamic exploration from landscape-scale to close-scale. Advected particles obey a Poisson-disk distribution in screen space.

Qizhi Yu is working on this topic as a Marie Curie PhD student (Visitor program), supervised by Fabrice Neyret and Eric Bruneton. The purpose is to obtain a realistical detailed appareance of landscape-long animated rivers in real-time, with user-editable features. The idea is to separate the river simulation into 3 scales, corresponding to different specification and simulation tools: macroscale for the topographic shape and global flow characteristics (relying on simple CFD at coarse resolution), mesoscopic scale for the local wave patterns (relying on dedicated phenomenological models), microscopic scale for the details (relying on textural procedural schemes). Note that this topic is included in the scope of the NatSim collaboration.

This year, we have developped a macroscopic model of rivers, allowing for the real-time visual simulation of a flow from close to far view on very large terrains (see Proland Project). A real-time editable vector description of river boundaries and obstacles is used to define a semi-analytic distance field which is use to derivate a zero-derivative flow. A screen-space Poisson-disk distribution of river particles carrying wave textures is animated and continuously readapted, so as to be space-time continuous (see Figure  12 ). A paper has been submmited.

Figure 13. Our Lagrangian texture advection model allows local patches to be deformed and regenerated asymchroneously. This yields a better conformance to the appearant flow and to the texture spectrum properties at the same time.

Moreover, we have developped a Lagrangian model of texture advection, to be used for advecting small water surface details while preserving their spectral characteristics. Our particles are distributed according to animated Poisson-disk, and carry a local grid mesh which is distorted by advection and regenerated when a distorsion metrics is passed. This Lagrangian approach solve the problem of local-adaptive regeneration rate, provide a better spectrum and better motion illusion, and avoid the burden of blending several layers (see Figure  13 ). A paper has been submmited.

Qizhi defended his PhD in November 2008 [6] .

The PhD of Mathieu Coquerelle  [2] , advised by Georges-Henri Cottet and co-advised by Marie-Paule Cani, explored the use of vortex particules for animating liquids and gases and to simulate their interactions with rigid solids. It was defended in September 2008.

Motion capture of small vertebrates

Participants : Estelle Duveau, Olivier Palombi, Lionel Reveret, Xiaomao Wu.

Figure 14. Motion capture of small vertebrates.

The ANR project Kameleon has driven several research topics towards the achievement of motion capture of small vertebrates. Works have been done to collect 3D scanner data of rat skeleton at very high resolution (up to 50 microns thanks to an experiment approved at the European Synchrotron Radiation Facility). The huge amount of tomography data has motivated development for GPU-based algorithm of surface segmentation. Anatomical skeletons have been processed to provide hierarchical skeleton for animation and registered onto video data. Several experiments have been conducted at the Museum National d’Histoire in Paris to collect video data. Estelle Duveau has started a PhD on motion capture from 3D surface flow. This PhD is co-advised by Lionel Reveret and U. Descartes, Paris 5. A clinical study is currently under investigation using techniques developed during the project and will be published in 2009.

Motion capture of animals in outdoor conditions

Participant : Lionel Reveret.

Figure 15. Motion capture of animals in outdoor conditions.

Projects have been started to develop method adapted to the motion capture of animals in outdoor conditions. A pioneer study has been done for greyhound dogs. The goal is to set-up a scientific campaign to perform motion capture in a wild life reserve in Africa.

Motion capture of trees under wind

Participants : Julien Diener, Lionel Reveret.

Figure 16. Motion capture of trees under wind.

These works are carried on in the context of the ANR project Chêne-Roseau. The goal is to validate measurement tool from video to evaluate the risk of breaking of fruit trees under strong wind. Several experiments have been done in collaboration with INRA at Clermont-Ferrand (UMR PIAF). In parallel, a work on modal analysis of tree structure and its application to real-time animation had been developed will be published at EG09.

Modeling motion capture data of human

Participants : Lionel Reveret, Maxime Tournier, Xiaomao Wu.

Figure 17. Modeling motion capture data of human.

Collaboration has been developed with the University of Montreal to address the problem of fall detection of elderly people. This work has been published at EMBC08. A continuation of this work is currently under investigation to integrate statistical descriptor of motion proposed in 2004 by Favreau et al. (SCA04) In addition, works on mathematical modeling of quaternionic signals arising from motion capture have been investigate within the context of the ARC project Fantastik. These works have lead to two INRIA Research Report and one paper will be published at EG09. Finally, works have been done on expressive facial animation with the Psychology Department of the University of Geneva. A journal paper is currently under preparation.


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