Visual Events of Convex Sets and Shadow Boundaries
Identifieur interne : 005291 ( Hal/Corpus ); précédent : 005290; suivant : 005292Visual Events of Convex Sets and Shadow Boundaries
Auteurs : Julien DemouthSource :
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Abstract
To compute shadows in computer graphics, it is common to be interested in the view of a geometric scene by an observer. Particularly, it is important to characterize the structural changes, called visual events, taking place in the view when the observer moves. Based on the combinatorial definition of view introduced by Gigus and Malik and the associated classification of visual events, many studies suffer from time and space complexity problems. For example, it is the case of discontinuity meshing. Thus, we suggest a new approach which relies on a questionning about this notion of view.
For a set of pairwise disjoint convex objects, we propose a topological definition of view emphasizing the visible silhouettes of objects in the scene and we geometrically characterize the locus where those visual events take place. We use this characterization to propose a method to extract boundaries between full light and penumbra and between penumbra and umbra in a scene lit by area light sources. We manage to strongly reduce the size of intermediate objects in use to build the limits between those regions.
Furthermore, we prove the first non trivial theoretical bounds on the complexity of the limits between full-light and penumbra and between penumbra and umbra.
For a set of pairwise disjoint convex objects, we propose a topological definition of view emphasizing the visible silhouettes of objects in the scene and we geometrically characterize the locus where those visual events take place. We use this characterization to propose a method to extract boundaries between full light and penumbra and between penumbra and umbra in a scene lit by area light sources. We manage to strongly reduce the size of intermediate objects in use to build the limits between those regions.
Furthermore, we prove the first non trivial theoretical bounds on the complexity of the limits between full-light and penumbra and between penumbra and umbra.
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Particularly, it is important to characterize the structural changes, called visual events, taking place in the view when the observer moves. Based on the combinatorial definition of view introduced by Gigus and Malik and the associated classification of visual events, many studies suffer from time and space complexity problems. For example, it is the case of discontinuity meshing. Thus, we suggest a new approach which relies on a questionning about this notion of view.
For a set of pairwise disjoint convex objects, we propose a topological definition of view emphasizing the visible silhouettes of objects in the scene and we geometrically characterize the locus where those visual events take place. We use this characterization to propose a method to extract boundaries between full light and penumbra and between penumbra and umbra in a scene lit by area light sources. We manage to strongly reduce the size of intermediate objects in use to build the limits between those regions.
Furthermore, we prove the first non trivial theoretical bounds on the complexity of the limits between full-light and penumbra and between penumbra and umbra.</div></front></TEI><hal api="V3"><titleStmt><title xml:lang="en">Visual Events of Convex Sets and Shadow Boundaries</title><title xml:lang="fr">Événements visuels de convexes et limites d'ombres</title><author role="aut"><persName><forename type="first">Julien</forename><surname>Demouth</surname></persName><email>julien.demouth@loria.fr</email><idno type="halauthor">216167</idno><affiliation ref="#struct-2573"></affiliation></author><editor role="depositor"><persName><forename>Julien</forename><surname>Demouth</surname></persName><email>julien.demouth@loria.fr</email></editor></titleStmt><editionStmt><edition n="v1" type="current"><date type="whenSubmitted">2008-11-28 12:13:45</date><date type="whenModified">2016-05-18 08:54:43</date><date type="whenReleased">2008-11-28 14:24:17</date><date type="whenProduced">2008-11-24</date><date type="whenEndEmbargoed">2008-11-28</date><ref type="file" target="https://tel.archives-ouvertes.fr/tel-00342717/document"><date notBefore="2008-11-28"></date></ref><ref type="file" n="1" target="https://tel.archives-ouvertes.fr/tel-00342717/file/these.pdf"><date notBefore="2008-11-28"></date></ref></edition><respStmt><resp>contributor</resp><name key="122237"><persName><forename>Julien</forename><surname>Demouth</surname></persName><email>julien.demouth@loria.fr</email></name></respStmt></editionStmt><publicationStmt><distributor>CCSD</distributor><idno type="halId">tel-00342717</idno><idno type="halUri">https://tel.archives-ouvertes.fr/tel-00342717</idno><idno type="halBibtex">demouth:tel-00342717</idno><idno type="halRefHtml">Modélisation et simulation. Université Nancy II, 2008. Français</idno><idno type="halRef">Modélisation et simulation. Université Nancy II, 2008. Français</idno></publicationStmt><seriesStmt><idno type="stamp" n="CNRS">CNRS - Centre national de la recherche scientifique</idno><idno type="stamp" n="INRIA">INRIA - Institut National de Recherche en Informatique et en Automatique</idno><idno type="stamp" n="INPL">Institut National Polytechnique de Lorraine</idno><idno type="stamp" n="LORIA2">Publications du LORIA</idno><idno type="stamp" n="INRIA-NANCY-GRAND-EST">INRIA Nancy - Grand Est</idno><idno type="stamp" n="LORIA-ACGI" p="LORIA">Algorithmique, calcul, image et géométrie</idno><idno type="stamp" n="LORIA">LORIA - Laboratoire Lorrain de Recherche en Informatique et ses Applications</idno><idno type="stamp" n="INRIA2">INRIA 2</idno><idno type="stamp" n="INRIA-LORRAINE">INRIA Nancy - Grand Est</idno><idno type="stamp" n="LABO-LORIA-SET" p="LORIA">LABO-LORIA-SET</idno><idno type="stamp" n="TDS-MACS">Réseau de recherche en Théorie des Systèmes Distribués, Modélisation, Analyse et Contrôle des Systèmes</idno><idno type="stamp" n="UNIV-LORRAINE">Université de Lorraine</idno></seriesStmt><notesStmt></notesStmt><sourceDesc><biblStruct><analytic><title xml:lang="en">Visual Events of Convex Sets and Shadow Boundaries</title><title xml:lang="fr">Événements visuels de convexes et limites d'ombres</title><author role="aut"><persName><forename type="first">Julien</forename><surname>Demouth</surname></persName><email>julien.demouth@loria.fr</email><idno type="halAuthorId">216167</idno><affiliation ref="#struct-2573"></affiliation></author></analytic><monogr><imprint><date type="dateDefended">2008-11-24</date></imprint><authority type="institution">Université Nancy II</authority><authority type="school">Mathématiques, Sciences et Technologies de l'Information (Informatique)</authority><authority type="supervisor">Hazel Everett(Hazel.Everett@loria.fr)</authority><authority type="jury">Guillaume Hanrot (président)</authority><authority type="jury">Hervé Brönnimann (rapporteur)</authority><authority type="jury">Nicolas Holzschuch (rapporteur)</authority><authority type="jury">Hazel Everett (directrice)</authority><authority type="jury">Xavier Goaoc (co-directeur)</authority><authority type="jury">Jean Ponce</authority></monogr></biblStruct></sourceDesc><profileDesc><langUsage><language ident="fr">French</language></langUsage><textClass><keywords scheme="author"><term xml:lang="en">Computational geometry</term><term xml:lang="en">computer graphics</term><term xml:lang="en">visual events</term><term xml:lang="en">shadow computation</term><term xml:lang="fr">Géométrie algorithmique</term><term xml:lang="fr">informatique graphique</term><term xml:lang="fr">événements visuels</term><term xml:lang="fr">synthèse d'ombres</term></keywords><classCode scheme="halDomain" n="info.info-mo">Computer Science [cs]/Modeling and Simulation</classCode><classCode scheme="halTypology" n="THESE">Theses</classCode></textClass><abstract xml:lang="en">To compute shadows in computer graphics, it is common to be interested in the view of a geometric scene by an observer. Particularly, it is important to characterize the structural changes, called visual events, taking place in the view when the observer moves. Based on the combinatorial definition of view introduced by Gigus and Malik and the associated classification of visual events, many studies suffer from time and space complexity problems. For example, it is the case of discontinuity meshing. Thus, we suggest a new approach which relies on a questionning about this notion of view.
For a set of pairwise disjoint convex objects, we propose a topological definition of view emphasizing the visible silhouettes of objects in the scene and we geometrically characterize the locus where those visual events take place. We use this characterization to propose a method to extract boundaries between full light and penumbra and between penumbra and umbra in a scene lit by area light sources. We manage to strongly reduce the size of intermediate objects in use to build the limits between those regions.
Furthermore, we prove the first non trivial theoretical bounds on the complexity of the limits between full-light and penumbra and between penumbra and umbra.</abstract><abstract xml:lang="fr">Pour le calcul d'ombres en informatique graphique, il est courant de s'intéresser à la vue qu'un observateur a d'une scène géométrique. En particulier, il est important de caractériser les changements structurels, appelés événements visuels, qui se produisent dans cette vue lorsque l'observateur se déplace. En se basant sur la définition combinatoire de la vue proposée par Gigus et Malik et la classification des événements visuels qui en découle, de nombreux travaux se heurtent à des problèmes de complexité en temps et en espace. C'est notamment le cas de la méthode du maillage de discontinuités. Nous suggérons donc une approche nouvelle qui repose sur la remise en cause de cette notion de vue.
Pour un ensemble d'objets convexes disjoints, nous proposons une définition topologique de la vue qui fait la part belle aux silhouettes visibles des objets de la scène et nous caractérisons géométriquement les lieux où se produisent les événements visuels. Nous utilisons cette caractérisation pour proposer une méthode qui permet d'extraire les limites entre lumière et pénombre et entre ombre et pénombre dans une scène éclairée par des sources surfaciques. Nous arrivons ainsi à réduire considérablement la taille des objets intermédiaires utilisés pour la construction des limites entre les régions.
De plus, nous démontrons les premières bornes théoriques non triviales sur la complexité des limites entre lumière et pénombre ainsi qu'entre ombre et pénombre.</abstract><particDesc><org type="consortium">VEGAS</org></particDesc></profileDesc></hal></record>Pour manipuler ce document sous Unix (Dilib)
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