Création automatique d'atlas de surfaces 3D en utilisant un algorithme de segmentation par seuillage récursif.

nombre de pages : 46 pages. Rapport de stage de DEA Informatique Théorique en 1993.L'utilisation des textures est très répandue en synthèse d'image pour accroître le réalisme. Le sujet de cette étude ne traite pas directement des textures mais de la façon dont on peut les plaquer le mieux possible sur la surface d'un objet. La solution est de découper cette surface en autant de parties qu'il sera nécessaire pour avoir une texture non déformée: il s'agit de la création d'atlas. Dans un premier temps, nous expliquerons les notions de texture, d'atlas, et le but poursuivi. Puis, deux types d'algorithme seront analysés: l'un de type ascendant, l'autre descendant et là aussi nous expliciterons davantage ces termes. Enfin, l'exploitation des résultats nous amènera à considérer certaines améliorations et quelques perspectives de recherche

Flocking as a Synchronization Phenomenon with Logistic Agents

International audienceIn this paper, we intend to show that the flocking phenomenon observed in many animal species behaviors, may be modeled as a synchronization process occurring within entity states. Although flocking has been widely studied and simulated in Swarm Intelligence, few works mention synchronization as a key aspect of the problem and model it properly. This paper proposes a modeling in terms of a reactive multi-agent system composed of interacting logistic agents moving in an environment. This specific MAS called Logistic MAS (LMAS) takes actually inspiration from the coupled map lattice field, which provides also many tools to analyse convergence and stability of the system. We develop our approach in both theoretical and applied way to demonstrate its relevance

A Nonlinear Multi-agent System designed for Swarm Intelligence : the Logistic MAS

International audienceAnt algorithms and flocking algorithms are the two main programming paradigms in swarm intelligence. They are built on stochastic models, widely used in optimization problems. However, though this modeling leads to high-performance algorithms, some mechanisms, like the symmetry break in ant decision, are still not well understood at the local ant level. Moreover, there is currently no modeling approach which joins the two paradigms. This paper proposes an entirely novel approach to the mathematical foundations of swarm algorithms: contrary to the current stochastic approaches, we show that an alternative deterministic model exists, which has its origin in deterministic chaos theory. We establish a reactive multi-agent system, based on logistic nonlinear decision maps, and designed according to the influence-reaction scheme. The rewriting of the decision functions leads to a new way of understanding the swarm phenomena in terms of state synchronization, and enables the analysis of their convergence behavior through bifurcation diagrams. We apply our approach on two concrete examples of each algorithm class, in order to demonstrate its general applicability

Study of Self-adaptation Mechanisms in a Swarm of Logistic Agents

International audienceWe are interested in addressing the problem of coordinating a large number of simple agents in order to achieve a given task. Stated in this way, the question leads naturally to the Swarm Intelligence field. In this paper we use a new type of model, directly inspired by Kaneko's coupled map gas model which we have adapted to the multi-agent system paradigm, so as to tackle this generic objective. This model is called a logistic multi-agent system (LMAS): it is composed of reactive situated agents whose individual behavior is governed by a logistic map or more generally a quadratic map. The collective behavior results from couplings between agents and local controls on agents adjusted by local environmental conditions. This way of modelling reveals to enable a wide range of pattern formations and various forms of adaptation to the environment. This paper focuses on the way to design the constitutive mechanisms of LMAS –particularly the perception and action processes– and on the way a self-adaptation process may result from these mechanisms. This study is illustrated with experiments on the predators-prey pursuit problem, in which a set of agents (predators) has to encircle a moving prey. We show that coupling the internal states of agents leads to amplifying the predator aggregation around the prey, whereas altering the internal control variable in each agent through environment perceptions modifies the predator sensitivity to the prey. We finally complete this study by relating the concept of adaptation with concepts of the dynamical system theory: a qualitative dynamical analysis of the capturing process leads to view the prey as a dynamical fixed point of the system

Deterministic Nonlinear Modeling of Ant Algorithm with Logistic Multi-Agent System

International audienceAnt algorithms are one of the main programming paradigms in swarm intelligence. They are built on stochastic decision functions, which can also be found in other types of bio-inspired algorithms with the same mathematical form. However, though this modeling leads to high-performance algorithms, some phenomena, like symmetry break, are still not well understood or modeled at the ant level. This paper proposes an original analysis of the problem : we establish a reactive multi-agent system based on logistic nonlinear decision maps, and designed according to the influence-reaction scheme. Our proposition is an entirely novel approach to the mathematical foundations of ant algorithms : contrary to the current stochastic approaches, we show that an alternative deterministic model exists, which has its origin in deterministic chaos theory. The rewriting of the decision functions leads to a new way of understanding and visualizing the convergence behavior of ant algorithms. We apply our approach on a concrete example, namely the binary bridge problem

Un modèle connexionniste pour l'intelligence en essaim : le système multi-agent logistique

National audienceLes approches connexionnistes sont un courant fort pour la modélisation de phénomènes complexes tels que les processus cérébraux en sciences cognitives, mais plus généralement pour la modélisation de systèmes complexes rencontrés dans de nombreux domaines. Ces approches sont soutenues par une famille de modèles mathématiques dits connexionnistes, fondamentalement déterministes, mettant en jeu des fonctions de transition non linéaires couplées par un réseau de connexions fixé à la conception du modèle. L'intelligence en essaim en revanche relève actuellement d'autres types de modèles, fortement bio-inspirés eux aussi, mais qui n'entrent pas explicitement dans le paradigme connexionniste. Nous montrerons ici qu'une approche connexionniste reste possible dans l'intelligence artificielle en essaim, moyennant certaines modifications structurelles et sémantiques des modèles connexionnistes. Cette démarche nous amène à concevoir un système multi-agent logistique résultant d'une vision dynamique de l'intelligence collective. Ce système sera mis en œuvre dans le cadre de deux cas d'études caractéristiques de la phénoménologie de l'intelligence artificielle en essaim, relatifs au comportement des colonies de fourmis d'une part et à la formation des nuées d'oiseaux d'autres part

Evaluation d'un prototype de campus virtuel 3D relativement à la problématique de " l'échec en licence "

8 pagesThe work described in this paper tackles the use of 3D web technologies at university, so as to respond to the academic failure problems. We aim in this way at quantifying the testing results of a 3Dcampus prototype on a group of student users at Nancy University. The goal is also to know why using such technologies may solve some specific problems linked with the welcome, the guidance, and the integration of students by "learning" their university.Le travail prospectif décrit dans cet article questionne l'usage des technologies de virtualisation 3D pour le web à l'Université dans la perspective de lutter contre " l'échec en licence ". Dans cette optique, on tente de mesurer l'impact auprès des étudiants d'un prototype 3D de campus virtuel à l'Université de Nancy. Il s'agit d'évaluer en quoi l'usage de ces technologies immersives peut répondre à certains aspects de l'accueil, de l'accompagnement et de l'intégration des étudiants primo-entrants à l'université par un " apprentissage " en simulation de leur université

Detection Algorithm of Chaotic Failures in a Directed Coupled Network

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A cascading failure model to study stress propagation in crowds

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Detection Algorithm of Chaotic Failures in a Directed Coupled Network

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