Towards Simulation of Handmade Painterly Animation

International audienceThis poster presents research in progress towards the simulation of handmade painterly animation. As researches on painterly animation mostly focus on temporal coherence, the generation of an animation that could have been done by hand remains an open challenging problem. To produce an hand made painterly animation, the artist paints on a retro-lighted glass canvas. He creates successive frames one over the other. The artist erase, smears and adds paint to produce each frame. We propose to render painterly animations with a visual aspect tending towards hand made results.To this end, we combines two techniques: an automatic strokes generator and a paint simulator. We observe that previous approaches could not adapt as-is to our goals for the two following reasons:Paint appearance in painterly animation is back lighted, most of paint contrast comes from paint thickness which is usually not compute by paint simulation approaches. Automatic strokes generation make the assumption that a stroke covers underlying strokes without having thickness accumulation, in our case paint thickness quickly increase if we do not apply special treatment. We also investigate new kind of strokes that are only possible with a paint simulation approach as smear and erase strokes

Un outil de dessin au trait pour le design d'une étude de caractérisation des lignes

National audienceUn outil de dessin au trait pour le design d'une étude de caractérisation des ligne

Contrôle artistique par édition de la propagation des rayons en photon mapping

National audiencePhysically based rendering with global illumination effects, has become a standard technique for high quality computer generated imagery. Nonetheless, being able to control the resulting picture so that it corresponds to the artist vision is still a tedious trial and error process. We introduce a path selection and edition metaphor, to give the artist a precise control over the final rendering without modifying the scene parameters. Starting from the identification of a lighting feature and its transcription in a path space regular expression, the proposed approach consists in selecting the corresponding light transport paths in 3D space and transforms them according to user defined operations.These operations affect both the geometry and the color spectrum of the paths.We demonstrate the wide range of control it permits on various lighting features, from low frequency color bleeding to high frequency caustics as well as view-dependent reflections.e rendu produisant des effets d'éclairement global est devenu un standard pour la synthèse d'image de haute qualité.Néanmoins, les graphistes ne peuvent éditer les images générées informatiquement qu'au prix d'un travail long et fastidieux sur la définition des sources de lumières et des matériaux de la scène 3D.Nous proposons une approche d'édition qui donne un contrôle précis sur le rendu final, sans modifier les paramètres de la scène 3D.À partir de l'identification d'un effet lumineux définie par une syntaxe d'interaction, l'approche consiste à sélectionner des chemins de transport lumineux et de les transformer suivant des opérations définies par le graphiste.Ces opérations sont des transformations sur la géométrie du transport lumineux ainsi que sur les spectres transportés par les chemins.Nous montrons la large gamme d'éditions que notre approche permet sur divers effets lumineux, allant des variations basses fréquences de diffusion indirecte de couleur, jusqu'aux variations hautes fréquences typiques des caustiques

Un outil de dessin au trait pour le design d'une étude de caractérisation des lignes

National audienceUn outil de dessin au trait pour le design d'une étude de caractérisation des ligne

Rendu expressif : communication visuelle et abstraction

communication oralecommunication oraleNational audienceno abstrac

Dynamic Stylized Shading Primitives

Honorable Mention in RenderingInternational audienceShading appearance in illustrations, comics and graphic novels is designed to convey illumination, material and surface shape characteristics at once. Moreover, shading may vary depending on different configurations of surface distance, lighting, character expressions, timing of the action, to articulate storytelling or draw attention to a part of an object. In this paper, we present a method that imitates such expressive stylized shading techniques in dynamic 3D scenes, and which offers a simple and flexible means for artists to design and tweak the shading appearance and its dynamic behavior. The key contribution of our approach is to seamlessly vary appearance by using a combination of shading primitives that take into account lighting direction, material characteristics and surface features. We demonstrate their flexibility in a number of scenarios: minimal shading, comics or cartoon rendering, glossy and anisotropic material effects; including a variety of dynamic variations based on orientation, timing or depth. Our prototype implementation combines shading primitives with a layered approach and runs in real-time on the GPU

Time and Space Coherent Occlusion Culling for Tileable Extended 3D Worlds

International audienceIn order to interactively render large virtual worlds, the amount of 3D geometry passed to the graphics hardware must be kept to a minimum. Typical solutions to this problem include the use of potentially visible sets and occlusion culling, however, these solutions do not scale well, in time nor in memory, with the size of a virtual world. We propose a fast and inexpensive variant of occlusion culling tailored to a simple tiling scheme that improves scalability while maintaining very high performance. Tile visibilities are evaluated with hardwareaccelerated occlusion queries, and in-tile rendering is rapidly computed using BVH instantiation and any visibility method; we use the CHC++ occlusion culling method for its good general performance. Tiles are instantiated only when tested locally for visibility, thus avoiding the need for a preconstructed global structure for the complete world. Our approach can render large-scale, diversified virtual worlds with complex geometry, such as cities or forests, all at high performance and with a modest memory footprint

An Efficient Trim Structure for Rendering Large B-Rep Models

International audienceWe present a multiresolution trim structure for fast and accurate B-Rep model visualization. To get a good tradeoff between performance and visual accuracy, we propose to use a vectorial but approximated representation of the model that allows efficient, real-time GPU exploitation. Our structure, based on a quadtree, enables us to do shallow lookups for distant fragments. For closeups, we leverage hardware tessellation. We get interactive frame rates for models that consists of hundreds of thousands of B-Rep faces, regardless of the zoom level

Une structure de découpe efficace pour l'affichage de grands modèles B-Rep

National audienceNous présentons une structure de découpe multirésolution pour l'affichage rapide et précis de modèles B-Rep. Nous proposons d'utiliser une représentation de la découpe de face basée sur un quadtree, autorisant une gestion efficace par le GPU. Ce quadtree contient des références à des courbes de découpe qui sont utilisées dans un fragment shader pour effectuer la classification de point d'une manière implicite. La façon dont sont stockées les informations multirésolution dans le quadtree nous permet de réduire les accès à notre structure lorsque les fragments sont distants de la caméra. Pour les objets en avant plan, nous nous appuyons sur la tessellation matérielle pour améliorer les performances, en réduisant la quantité de calcul à effectuer pour chaque fragment. Nous obtenons un affichage intéractif pour de très gros modèles comprenant des centaines de milliers de faces B-Rep, quel que soit le niveau de zoom