Soft Textured Shadow Volume

International audienceEfficiently computing robust soft shadows is a challenging and time consuming task. On the one hand, the quality of image-based shadows is inherently limited by the discrete property of their framework. On the other hand, object-based algorithms do not exhibit such discretization issues but they can only efficiently deal with triangles having a constant transmittance factor. This paper addresses this limitation. We propose a general algorithm for the computation of robust and accurate soft shadows for triangles with a spatially varying transmittance. We then show how this technique can be efficiently included into object-based soft shadow algorithms. This results in unified object-based frameworks for computing robust direct shadows for both standard and perforated triangles in fully animated scenes

Real-Time Hierarchical Binary-Scene Voxelization

International audienceVolumetric representations provide the localization of shapes in space. When such representation is created on the fly from the geometry, it becomes very useful for a wide range of applications (constructive solid geometry (CSG), shape repair , collision detection, etc. Using the advanced functionalities provided by recent GPUs (geometry shaders, 32-bit integer texture format and bitwise operators), we show how to compute a robust scene voxelization and octree construction in a few milliseconds from any hardware-supported rasterizable geometry. Our hierarchical volumetric representation is thus especially well-suited for hierarchical computation of fully dynamic scenes

Accurate Shadows by Depth Complexity Sampling

International audience(a) (b) (c) Figure 1: High quality shadows produced by our algorithm. The 1024×1024 images are computed in 4 seconds on a traditional Japanese scene composed of 501, 650 triangles, semi-opaque occluders and 4 omni-directional area lights. Abstract The accurate generation of soft shadows is a particularly computationally intensive task. In order to reduce rendering time, most real-time and offline applications decorrelate the generation of shadows from the computation of lighting. In addition to such approximations, they generate shadows using some restrictive assumptions only correct in very specific cases, leading to penumbra over-estimation or light-leaking artifacts. In this paper we present an algorithm that produces soft shadows without exhibiting the previous drawbacks. Using a new efficient evaluation of the number of occluders between two points (i.e. the depth complexity) we either modulate direct lighting or numerically solve the rendering equation for direct illumination. Our approach approximates shadows cast by semi-opaque occluders and naturally handles area lights with spatially varying luminance. Furthermore, depending on the desired performance and quality, the resulting shadows are either very close to, or as accurate as, a ray-traced reference. As a result, the presented method is well suited to many domains, ranging from quality-sensitive to performance-critical applications

Applications

Systèmes de Liénard et décomposition potentielle-Hamiltonienn

Realistic soft shadows by penumbra-wedges blending

International audienceRecent real-time shadow generation techniques try to provide shadows with realistic penumbrae. However, most techniques are whether non-physically based or too simplified to produce convicing results. The penumbra-wedges algorithm is a physical approach based on the assumption that penumbrae are non-overlapping. In this paper, we propose an algorithm that takes the advantages of the penumbra-wedges method but solves the "non-overlapping" limitation. We first compute the light occlusion regions per fragment. Then we use this information to detect the areas where penumbrae are overlapping and we perform a realistic penumbra blending