11 research outputs found
Preprocessing Imprecise Points for Delaunay Triangulation: Simplified and Extended
Suppose we want to compute the Delaunay triangulation of a set P whose points are restricted to a collection R of input regions known in advance. Building on recent work by Löffler and Snoeyink, we show how to leverage our knowledge of R for faster Delaunay computation. Our approach needs no fancy machinery and optimally handles a wide variety of inputs, e.g., overlapping disks of different sizes and fat regions. Keywords: Delaunay triangulation - Data imprecision - Quadtree
Vertical ray shooting and computing depth orders of fat objects
We present new results for three problems dealing with a set of convex constant-complexity fat polyhedra in 3-space. (i) We describe a data structure for vertical ray shooting in that has query time and uses storage. (ii) We give an algorithm to compute in time a depth order on if it exists. (iii) We give an algorithm to verify in time whether a given order on is a valid depth order. All three results improve on previous results
Lâauto-exploration des espaces sensorimoteurs chez les robots
Developmental robotics has begun in the last fifteen years to study robots that havea childhoodâcrawling before trying to run, playing before being usefulâand that are basing their decisions upon a lifelong and embodied experience of the real-world. In this context, this thesis studies sensorimotor explorationâthe discovery of a robotâs own body and proximal environmentâduring the early developmental stages, when no prior experience of the world is available. Specifically, we investigate how to generate a diversity of effects in an unknown environment. This approach distinguishes itself by its lack of user-defined reward or fitness function, making it especially suited for integration in self-sufficient platforms. In a first part, we motivate our approach, formalize the exploration problem, define quantitative measures to assess performance, and propose an architectural framework to devise algorithms. through the extensive examination of a multi-joint arm example, we explore some of the fundamental challenges that sensorimotor exploration faces, such as high-dimensionality and sensorimotor redundancy, in particular through a comparison between motor and goal babbling exploration strategies. We propose several algorithms and empirically study their behaviour, investigating the interactions with developmental constraints, external demonstrations and biologicallyinspired motor synergies. Furthermore, because even efficient algorithms can provide disastrous performance when their learning abilities do not align with the environmentâs characteristics, we propose an architecture that can dynamically discriminate among a set of exploration strategies. Even with good algorithms, sensorimotor exploration is still an expensive propositionâ a problem since robots inherently face constraints on the amount of data they are able to gather; each observation takes a non-negligible time to collect. [...] Throughout this thesis, our core contributions are algorithms description and empirical results. In order to allow unrestricted examination and reproduction of all our results, the entire code is made available. Sensorimotor exploration is a fundamental developmental mechanism of biological systems. By decoupling it from learning and studying it in its own right in this thesis, we engage in an approach that casts light on important problems facing robots developing on their own.La robotique dĂ©veloppementale a entrepris, au courant des quinze derniĂšres annĂ©es,dâĂ©tudier les processus dĂ©veloppementaux, similaires Ă ceux des systĂšmes biologiques,chez les robots. Le but est de crĂ©er des robots qui ont une enfanceâqui rampent avant dâessayer de courir, qui jouent avant de travaillerâet qui basent leurs dĂ©cisions sur lâexpĂ©rience de toute une vie, incarnĂ©s dans le monde rĂ©el.Dans ce contexte, cette thĂšse Ă©tudie lâexploration sensorimotriceâla dĂ©couverte pour un robot de son propre corps et de son environnement procheâpendant les premiers stage du dĂ©veloppement, lorsque quâaucune expĂ©rience prĂ©alable du monde nâest disponible. Plus spĂ©cifiquement, cette thĂšse se penche sur comment gĂ©nĂ©rer une diversitĂ© dâeffets dans un environnement inconnu. Cette approche se distingue par son absence de fonction de rĂ©compense ou de fitness dĂ©finie par un expert, la rendant particuliĂšrement apte Ă ĂȘtre intĂ©grĂ©e sur des robots auto-suffisants.Dans une premiĂšre partie, lâapproche est motivĂ©e et le problĂšme de lâexploration est formalisĂ©, avec la dĂ©finition de mesures quantitatives pour Ă©valuer le comportement des algorithmes et dâun cadre architectural pour la crĂ©ation de ces derniers. Via lâexamen dĂ©taillĂ© de lâexemple dâun bras robot Ă multiple degrĂ©s de libertĂ©, la thĂšse explore quelques unes des problĂ©matiques fondamentales que lâexploration sensorimotrice pose, comme la haute dimensionnalitĂ© et la redondance sensorimotrice. Cela est fait en particulier via la comparaison entre deux stratĂ©gies dâexploration: le babillage moteur et le babillage dirigĂ© par les objectifs. Plusieurs algorithmes sont proposĂ©s tour Ă tour et leur comportement est Ă©valuĂ© empiriquement, Ă©tudiant les interactions qui naissent avec les contraintes dĂ©veloppementales, les dĂ©monstrations externes et les synergies motrices. De plus, parce que mĂȘme des algorithmes efficaces peuvent se rĂ©vĂ©ler terriblement inefficaces lorsque leurs capacitĂ©s dâapprentissage ne sont pas adaptĂ©s aux caractĂ©ristiques de leur environnement, une architecture est proposĂ©e qui peut dynamiquement choisir la stratĂ©gie dâexploration la plus adaptĂ©e parmi un ensemble de stratĂ©gies. Mais mĂȘme avec de bons algorithmes, lâexploration sensorimotrice reste une entreprise coĂ»teuseâun problĂšme important, Ă©tant donnĂ© que les robots font face Ă des contraintes fortes sur la quantitĂ© de donnĂ©es quâils peuvent extraire de leur environnement;chaque observation prenant un temps non-nĂ©gligeable Ă rĂ©cupĂ©rer. [...] Ă travers cette thĂšse, les contributions les plus importantes sont les descriptions algorithmiques et les rĂ©sultats expĂ©rimentaux. De maniĂšre Ă permettre la reproduction et la rĂ©examination sans contrainte de tous les rĂ©sultats, lâensemble du code est mis Ă disposition. Lâexploration sensorimotrice est un mĂ©canisme fondamental du dĂ©veloppement des systĂšmes biologiques. La sĂ©parer dĂ©libĂ©rĂ©ment des mĂ©canismes dâapprentissage et lâĂ©tudier pour elle-mĂȘme dans cette thĂšse permet dâĂ©clairer des problĂšmes importants que les robots se dĂ©veloppant seuls seront amenĂ©s Ă affronter
Guarding scenes against invasive hypercubes
AbstractIn recent years realistic input models for geometric algorithms have been studied. The most important models introduced are fatness, low density, unclutteredness and small simple-cover complexity. These models form a strict hierarchy. Unfortunately, small simple-cover complexity is often too general to enable efficient algorithms. In this paper we introduce a new model based on guarding sets. Informally, a guarding set for a collection of objects is a set of points that approximates the distribution of the objects. Any axis-parallel hyper-cube that contains no guards in its interior may intersect at most a constant number of objects. We show that guardable scenes fit in between unclutteredness and small simple-cover complexity. They do enable efficient algorithms, for example a linear size binary space partition. We study properties of guardable scenes and give heuristic algorithms to compute small guarding sets
Guarding Scenes against Invasive Hypercubes
In recent years realistic input models for geometric algorithms have been studied. The most important models introduced are fatness, low density, unclutteredness, and small simple-cover complexity. These models form a strict hierarchy. Unfortunately, small simple-cover complexity is often too general to enable efficient algorithms. In this paper we introduce a new model based on guarding sets. Informally, a guarding set for a collection of objects is a set of points that approximates the distribution of the objects. Any axisparallel hypercube that contains no guards in its interior may intersect at most a constant number of objects. We show that guardable scenes fit in between unclutteredness and small simple-cover complexity. They do enable efficient algorithms, for example a linear size binary space partition. We study properties of guardable scenes and give heuristic algorithms to compute small guarding sets