Cinématographie et montage automatique dans des environnements virtuels

The wide availability of high-resolution 3D models and the facility to create new geometrical and animated content, using low-cost input devices, opens to many the possibility of becoming digital 3D storytellers. To date there is however a clear lack of accessible tools to easily create the cinematography (positioning and moving the cameras to create shots) and perform the editing of such stories (selecting appropriate cuts between the shots created by the cameras). Creating a movie requires the knowledge of a significant amount of empirical rules and established conventions. In particular continuity editing -- the creation of a sequence of shots ensuring visual continuity -- is a complex endeavor. Most 3D animation packages lack continuity editing tools, calling the need for automatic approaches that would, at least partially, support users in their creative process.In this thesis we address both challenges of automating cinematography and editing in virtual environments. In a first contribution we propose a system that relies on Reynolds' model of steering behaviors to control and locally coordinate a collection of camera agents in dynamic 3D environments. The second contribution consists of a novel optimization-based approach for automatically creating well-edited movies from a 3D animation. We propose an efficient solution through dynamic programming, by relying on a plausible semi-Markov assumption. The next contribution uses and extends our previous work to propose a novel importance-driven approach to cinematic replay that exploits both the narrative and geometric information in games to automatically compute camera paths and edits. Finally, our last contribution addresses camera control issues by constraining motion on camera rails to ensure realistic shots.La libre diffusion de modèles 3D de qualité ainsi que la mise à disposition de nombreux moyens facilitant la création de contenus animés ont permis de populariser la production d'oeuvres cinématographiques 3D. A l'heure actuelle, on peut cependant observer un manque important d'outils permettant de traiter la cinématographie (placement des caméras pour l'enregistrement des plans) et d'effectuer le montage de tels contenus (sélection des plans et transitions entre caméras). La création d'un film nécessite la connaissance d'un grand nombre de règles et de conventions. A travers cette thèse, nous proposons de nouvelles méthodes et de nouveaux outils permettant, au moins partiellement, d'aider les utilisateurs à réaliser la cinématographie et le montage de leurs productions