Représentation, modélisation et génération procédurale de terrains

Slides disponiblesSoutenance oral (présentation + questions) disponible sur demandeThis PhD (entitled "Representation, modelisation and procedural generation of terrains") is related to movie and videogames digital content creation, especially natural scenes.Our work is dedicated to handle and to generate landscapes efficently. We propose a new model based on a construction tree inside which the user can handle parts of the terrain intuitively. We also present techniques to efficently visualize such model. Finally, we present a new algorithm for generating large-scale terrains exhibiting hierarchical structures based on their hydrographic networks: elevation is generated in a broad compliance to water-tansport principles without having to resort on costly hydraulic simulations.Cette thèse (qui a pour intitulé "Représentation, modélisation et génération procédurale de terrains") a pour cadre la génération de contenus numériques destinés aux films et aux jeux-vidéos, en particulier les scènes naturelles.Nos travaux visent à représenter et à générer des terrains. Nous proposons, en particulier, un nouveau modèle de représentation qui s'appuie sur un arbre de construction et qui va permettre à l'utilisateur de manipuler des morceaux de terrain de façon intuitive. Nous présentons également des techniques pour visualiser ce modèle avec un maximum d'efficacité. Enfin nous développons un nouvel algorithme de génération de terrains qui construit de très grands reliefs possédant des structures hiérarchiques découlant d'un réseau hydrographique : le relief généré est conforme aux grands principes d'écoulement des eaux sans avoir besoin d'utiliser de coûteuses simulations d'érosion hydrique

Computer graphics simulation of organic and inorganic optical and morphological appearance changes.

Organic bodies are subject to internal biological, chemical and physical processes as well as environmental interactions after death, which cause significant structural and optical changes. Simulating corpse decomposition and the environmental effects on its surface can help improve the realism of computer generated scenes and provide the impression of a living, dynamic environment. The aim of this doctorate thesis is to simulate post mortem processes of the human body and their visual effects on its appearance. The proposed method is divided into three processes; surface weathering due to environmental activities, livor mortis and natural mummification by desiccation. The decomposing body is modelled by a layered model consisting of a tetrahedral mesh representing the volume and a high resolution triangle surface mesh representing the skin. A particle-based surface weathering approach is employed to add environmental effects. The particles transport substances that are deposited on the object’s surface. A novel, biologically-inspired blood pooling simulation is used to recreate the physical processes of livor mortis and its visual effects on the corpse’s appearance. For the mummification, a physically-based approach is used to simulate the moisture diffusion process inside the object and the resulting de- formations of the volume and skin. In order to simulate the colouration changes associated with livor mortis and mummification, a chemically-based layered skin shader that considers time and spatially varying haemoglobin, oxygen and moisture contents is proposed. The suggested approach is able to model changes in the internal structure and the surface appearance of the body that resemble the post mortem processes livor mortis, natural mummification by desiccation and surface weathering. The surface weathering approach is able to add blemishes, such as rust and moss, to an object’s surface while avoiding inconsistencies in deposit sizes and dis- continuities on texture seams. The livor mortis approach is able to model the pink colouration changes caused by blood pooling, pressure induced blanching effects, fixation of hypostasis and the purple discolouration due to oxygen loss in blood. The mummification method is able to reproduce volume shrinkage effects caused by moisture loss, skin wrinkling and skin darkening that are comparable to real mummies