Implantation temps réel sur GPU d'un écran d'épingles dynamique

Actes: http://liris.cnrs.fr/publis/?id=4183National audienceCet article présente une implantation temps réel sur processeur graphique de la méthode dite de l’écran d’épingles dynamique inspiré de la méthode de gravure d’Alexandre Alexeïeff. Cette méthode initialement, proposée par [HL02] et fondée sur un formalisme masses- interactions, était trop coûteuse pour pouvoir s’insérer dans une application interactive. Cet article résout ce frein majeur à l’exploration des possibilités dynamiques de la méthode. Il présente alors un certain nombre d’applications obtenues en temps-réel : (1) la visualisation de modèles particulaires simulés sur une machine amont en temps réel ou en temps différé, (2) l’utilisation de l’écran d’épingles dynamique comme modèle physique pour des scènes 3D complexes, (3) une gravure directe par l’intermédiaire de la souris

Physical models of loose soils dynamically marked by a moving object

International audienceIn the field of robotics, some autonomous vehicles work in natural sites. One problem for the autonomous system is to plan a path to the goal. A usual method use potential field to find a global patch. With this method, obstacles must be clearly defined. But this is not the case in such natural environments. A new physicaly based potential method is introduced to find patchs as, for instance, a winding path to a pass

Physical Models of Loose Soils Dynamically Marked by a Moving Object

International audienceThis paper deals with the modeling of loose soil (sandy, muddy, etc.). When an object moves on such grounds, the object's and the soil's movement both depend the mutual physical interactions, and therefore are very difficult to achieve kinematic or geometric models. We use a particle-based dynamic modeler and achieve a discrete model of plasticity which accounts for the influence of the soil on objects moving on this soil, but also for the influence of the object on the movement and the shape of the soil.no abstrac

A Framework for Dynamic Terrain with Application in Off-road Ground Vehicle Simulations

The dissertation develops a framework for the visualization of dynamic terrains for use in interactive real-time 3D systems. Terrain visualization techniques may be classified as either static or dynamic. Static terrain solutions simulate rigid surface types exclusively; whereas dynamic solutions can also represent non-rigid surfaces. Systems that employ a static terrain approach lack realism due to their rigid nature. Disregarding the accurate representation of terrain surface interaction is rationalized because of the inherent difficulties associated with providing runtime dynamism. Nonetheless, dynamic terrain systems are a more correct solution because they allow the terrain database to be modified at run-time for the purpose of deforming the surface. Many established techniques in terrain visualization rely on invalid assumptions and weak computational models that hinder the use of dynamic terrain. Moreover, many existing techniques do not exploit the capabilities offered by current computer hardware. In this research, we present a component framework for terrain visualization that is useful in research, entertainment, and simulation systems. In addition, we present a novel method for deforming the terrain that can be used in real-time, interactive systems. The development of a component framework unifies disparate works under a single architecture. The high-level nature of the framework makes it flexible and adaptable for developing a variety of systems, independent of the static or dynamic nature of the solution. Currently, there are only a handful of documented deformation techniques and, in particular, none make explicit use of graphics hardware. The approach developed by this research offloads extra work to the graphics processing unit; in an effort to alleviate the overhead associated with deforming the terrain. Off-road ground vehicle simulation is used as an application domain to demonstrate the practical nature of the framework and the deformation technique. In order to realistically simulate terrain surface interactivity with the vehicle, the solution balances visual fidelity and speed. Accurately depicting terrain surface interactivity in off-road ground vehicle simulations improves visual realism; thereby, increasing the significance and worth of the application. Systems in academia, government, and commercial institutes can make use of the research findings to achieve the real-time display of interactive terrain surfaces

Visual modeling and simulation of multiscale phenomena

Many large-scale systems seen in real life, such as human crowds, fluids, and granular materials, exhibit complicated motion at many different scales, from a characteristic global behavior to important small-scale detail. Such multiscale systems are computationally expensive for traditional simulation techniques to capture over the full range of scales. In this dissertation, I present novel techniques for scalable and efficient simulation of these large, complex phenomena for visual computing applications. These techniques are based on a new approach of representing a complex system by coupling together separate models for its large-scale and fine-scale dynamics. In fluid simulation, it remains a challenge to efficiently simulate fine local detail such as foam, ripples, and turbulence without compromising the accuracy of the large-scale flow. I present two techniques for this problem that combine physically-based numerical simulation for the global flow with efficient local models for detail. For surface features, I propose the use of texture synthesis, guided by the physical characteristics of the macroscopic flow. For turbulence in the fluid motion itself, I present a technique that tracks the transfer of energy from the mean flow to the turbulent fluctuations and synthesizes these fluctuations procedurally, allowing extremely efficient visual simulation of turbulent fluids. Another large class of problems which are not easily handled by traditional approaches is the simulation of very large aggregates of discrete entities, such as dense pedestrian crowds and granular materials. I present a technique for crowd simulation that couples a discrete per-agent model of individual navigation with a novel continuum formulation for the collective motion of pedestrians. This approach allows simulation of dense crowds of a hundred thousand agents at near-real-time rates on desktop computers. I also present a technique for simulating granular materials, which generalizes this model and introduces a novel computational scheme for friction. This method efficiently reproduces a wide range of granular behavior and allows two-way interaction with simulated solid bodies. In all of these cases, the proposed techniques are typically an order of magnitude faster than comparable existing methods. Through these applications to a diverse set of challenging simulation problems, I demonstrate the benefits of the proposed approach, showing that it is a powerful and versatile technique for the simulation of a broad range of large and complex systems

MIMESIS, un environnement de conception et de simulation de modèles physiques particulaires masses-interactions CORDIS-ANIMA pour l'animation : du mouvement généré à l'image du mouvement

This thesis deals with the design of a computer framework dedicaced to animation by the physical mass-interaction CORDIS-ANIMA networks. Genericity and modularity of CORDIS-ANIMA having been still largely proved, the design and the implementation of such framework have to face with other theorical and practical problems that are discussed here in order to include every function that are required for an interactive creation of models and the communication inside a global chain of production of animated pictures. This thesis ends on the report of various situation of use in pedagogical, research and creation contexts.Cette thèse a pour objet la conception d’un environnement pour l’animation à l’aide de réseaux masses–interactions CORDIS-ANIMA. La généricité et la modularité de CORDIS-ANIMA ayant largement prouvé leur intérêt pour l’animation depuis 25 ans, la conception et l’implantation d’un environnement de conception de tels modèles doivent faire face à d’autres problématiques théoriques et pratiques qui seront discutées dans ce manuscrit, dans le but d’inclure dans cet environnement toutes les fonctionnalités requises pour une création interactive de modèles de mouvement et leur insertion dans une chaîne globale de production d’images animées. Cette thèse se terminera par le compte-rendu de situations d’utilisation dans un cadre pédagogique, de recherche et de création