We introduce an image‐based representation, called volumetric billboards, allowing for the real‐time rendering of semi‐transparent and visually complex objects arbitrarily distributed in a 3D scene. Our representation offers full parallax effect from any viewing direction and improved anti‐aliasing of distant objects. It correctly handles transparency between multiple and possibly overlapping objects without requiring any primitive sorting. Furthermore, volumetric billboards can be easily integrated into common rasterization‐based renderers, which allows for their concurrent use with polygonal models and standard rendering techniques such as shadow‐mapping.

Level set methods have been extensively used to track the dynamical interfaces between different materials for physically based simulation, geometry modeling, oceanic modeling and other scientific and engineering applications. Due to the inherent Eulerian characteristics, interface evolution based on level set usually suffers from numerical diffusion, sharp feature missing and mass loss. Although some effective methods such as Particle Level Set (PLS) and Marker Level Set (MLS) have been proposed to tackle these difficulties, the complicated correction process and the high computational cost pose severe limitations for real-time applications. In this paper we provide an efficient parallel implementation of the Marker Level Set method on latest graphics hardware. Each step of the MLS method is fully mapped on GPU with an innovative combination of different computation techniques. Relying on GPU's parallelism and flexible programmability, the method provides real-time performance for large size 2D examples and moderate 3D examples, which is significantly faster than previous CPU-based methods.

Interactive volume rendering methods such as texture-based slicing techniques and ray casting have been well developed in recent years. The rendering performance is generally restricted by the volume size, the fill-rate, and the texture fetch speed of the graphics hardware. For most 3D data sets, a fraction of the volume is empty, which will reduce the rendering performance without specific optimization. In this paper, we present a simple kd-tree-based space partitioning scheme to efficiently remove the empty spaces from the volume data sets at the preprocessing stage. The splitting rule of the scheme is based on a simple yet effective cost function evaluated through a fast approximation of the bounding volume of the nonempty regions. The scheme culls a large number of empty voxels and encloses the remaining data with a small number of axis-aligned bounding boxes, which are then used for interactive rendering. The number of boxes is controlled by halting criteria. In addition to its simplicity, our scheme requires little preprocessing time and improves the rendering performance significantly.

Modeling dressed characters is known as a very tedious process. It usually requires specifying 2D fabric patterns, positioning and assembling the min 3D, and then performing a physically‐based simulation. The latter accounts for gravity and collisions to compute the rest shape of the garment, with the adequate folds and wrinkles.

Abstract: We present a new, procedural approach for modelling and animating the garments worn by virtual characters. Our method

We present a new, procedural approach for modelling and animating the garments worn by virtual characters. Our method takes into account the properties of fabric to generate the geometry of local folds that are so crucial for visual realism. Modelling is performed by approximating an initial free-form surface roughly representing a garment by a piecewise developable mesh called the buckling mesh. The latter models the specific buckling features of fabric: more precisely, it automatically folds according to pre-computed patterns, depending on the 3D positions of a few control points. The approximation enhances the realism of the garment surface since the wrinkles that make it piecewise developable also give it the appearance of fabric. Moreover, the set of 2D fabric panels required to sew the garment is computed during the process, enabling distortion-free texture mapping. During animation, the buckling mesh procedurally folds and unfolds according to the positions of its control points. The latter are animated through a simple physically-based model that accounts for the floating behaviour of cloth. Our solution differs completely from the standard physically-based approach, since it does not require the use of many mass nodes nor of stiff equations to generate non-extensible cloth. As our results show, our method can be used for the real-time, visually aesthetic animation of dressed characters, making it applicable to enhance the realism of virtual humans in real-time applications. Key-words: cloth modelling, procedural models, real-time animation ∗ GRAVIR/IMAG-INRIA, projet EVASION – 655 avenue de l’Europe – 38334 Montbonnot Saint-Ismier – France . Email: philippe.decaudin@(NOSPAM) imag.fr – Web: http://www.antisphere.com † University of Tübingen, WSI/GRIS – Sand 14 – 72076 Tübingen – Germany . Email: b.thomaszewski@(NOSPAM) gmx.de ‡ GRAVIR/IMAG-INRIA, projet EVASION – 655 avenue de l’Europe – 38334 Montbonnot Saint-Ismier – France . Email: marie-paule.cani@(NOSPAM) imag.fr – Web: http://www-evasion.imag.fr/Membres/Marie-Paule.Cani/ Vêtements virtuels basés sur les propriétés de flambage du tissu Résumé : Nous présentons une nouvelle approche procédurale pour modéliser et animer des vêtements portés par des acteurs virtuels. Notre méthode se base sur les propriétés des tissus pour générer la géométrie des plis qui apparaissent localement sur les vêtements. Ces plis sont d’une grande importance pour le réalisme visuel. La modélisation est obtenue en approximant une surface initiale arbitraire représentant approximativement le vêtement par un maillage développable par morceaux appelé le maillage de flambage. Ce dernier modélise les propriétés de flambage spécifiques au tissu : plus précisément, il se plie automatiquement en fonction de motifs pré-définis, qui dépendent de la position d’un petit nombre de points de contrôles. Ceci augmente le réalisme du vêtement car ces plis qui rendent sa surface développable par morceaux lui confèrent aussi l’apparence d’un tissu. De plus, les patrons 2D de tissu nécessaires pour coudre le vêtement sont calculés pendant le processus, permettant ainsi de le texturer sans distorsion. Au cours de l’animation, le maillage de flambage se plie et se déplie procéduralement en fonction des positions de ses points de contrôle. Ceux-ci sont animés par un modèle physique simple qui simule le comportement des parties flottantes du vêtement. Notre solution diffère totalement des approches physiques standards, car elle ne nécessite pas l’utilisation de beaucoup de masses ni de ressorts de fortes raideurs pour obtenir un vêtement non-extensible. Comme le montre nos résultats, notre méthode peut être utilisée pour l’animation en temps-réel de personnages habillés, la rendant utile pour améliorer le réalisme d’humains virtuels dans les applications temps-réelles. Mots-clés : modélisation de vêtements, modèles procéduraux, animation en temps-réel Virtual garments based on geometric features of fabric buckling 3

Forests are crucial for scene realism in applications such as light simulators. This paper proposes a new representation allowing for the real-time rendering of realistic forests covering an arbitrary terrain. It lets us produce dense forests corresponding to continuous non-repetitive fields made of thousands of trees with full parallax. Our representation draws on volumetric textures and aperiodic tiling: the forest consists of a set of edgecompatible prisms containing forest samples which are aperiodically mapped onto the ground. The representation allows for quality rendering, thanks to appropriate 3D non-linearfiltering. It relies on LODs and on a GPUfriendly structure to achieve real-time performance. Dynamic lighting and shadowing are beyond the scope of this paper. On the other hand, we require no advanced graphics feature except 3D textures and decent fill and vertex transform rates. However we can take advantage of vertex shaders so that the slicing of the volumetric texture is entirely done on the GPU.

Rendering realistic natural scenes in real-time is a challenging topic in the field of computer graphics. More specifically, we want to render scenes that contain complex shapes bounded in a layer above a surface. Landscapes (e.g., terrain, vegetation) are examples of such scenes. Lightings and shadows are essential elements toward realism because they help understanding shapes. However: - Using polygonal meshes and classical shadowing algorithms are too costly in terms of computation for complex scenes; - Adapted algorithms for dedicated representations such height-fields are efficient, but these representations are too limited for our needs (e.g. forest); - Although more powerful representations like surfels or texels exist, algorithms for quality and efficient lighting and shadowing are not available yet. Thus, our goal is to propose lighting and shadowing techniques adapted to such representations as well as the GPU.

This paper deals with the packing of square tiles of the same size into one texture. Texture size is constrained by the graphics hardware. In particular, width and height resolutions must be powers of two. To cover the whole texture and avoid space loss, common schemes pack a number of tiles that is a power of two. We show that numbers of tiles like 5, 13, 17, 25, 34 and others can also be reached without wasting memory. To achieve this, our scheme takes advantage of texture rotation and the wrapping capability of texture-addressing, which gives a torus topology to the texture space.

We present a new, procedural approach for modelling and animating the garments worn by virtual characters. Our method takes into account the properties of fabric to generate the geometry of local folds that are so crucial for visual realism. Modelling is performed by approximating an initial free-form surface roughly representing a garment by a piecewise developable mesh called the buckling mesh. The latter models the specific buckling features of fabric: more precisely, it automatically folds according to pre-computed patterns, depending on the 3D positions of a few control points. The approximation enhances the realism of the garment surface since the wrinkles that make it piecewise developable also give it the appearance of fabric. Moreover, the set of 2D fabric panels required to sew the garment is computed during the process, enabling distortion-free texture mapping. During animation, the buckling mesh procedurally folds and unfolds according to the positions of its control points. The latter are animated through a simple physically-based model that accounts for the floating behaviour of cloth. Our solution differs completely from the standard physically-based approach, since it does not require the use of many mass nodes nor of stiff equations to generate non-extensible cloth. As our results show, our method can be used for the real-time, visually aesthetic animation of dressed characters, making it applicable to enhance the realism of virtual humans in real-time applications.