MODELING, ANIMATING, AND RENDERING COMPLEX SCENES USING VOLUMETRIC TEXTURES

Complex repetitive scenes containing forests, foliage, grass, hair, or fur, are challenging for common modeling and rendering tools. The amo unt of data, the tediousness of modeling and animation tasks, and the cost of realistic rendering have caused such kind of scene to see only limited use even in high-end productions. We describe here how the us e of Volumetric textures is well suited to such scenes. These primitiv es can greatly simplify modeling and animation tasks. More importantly , they can be very efficiently rendered using ray tracing with few ali asing artifacts. The main idea, initially introduced by Kajiya and Kay [9], is to represent a pattern of 3D geometry in a reference volume, that is tiled over an underlying surface much like a regular 2D textur e. In our contribution, the mapping is independent of the mesh subdivi sion, the pattern can contain any kind of shape, and ii is prefiltered at different scales as for MIP-mapping. Although the model encoding i s volumetric, the rendering method differs greatly from traditional vo lume rendering:A volumetric texture only exists in the neighborhood of a surface, and the repeated instances (called texels) of the referenc e volume are spatially deformed. Furthermore, each voxel of the refere nce volume contains a key feature which controls the reflectance funct ion that represents aggregate intravoxel geometry. This allows for ray -tracing of highly complex scenes with very few aliasing artifacts, us ing a single ray per pixel (for the part of the scene using the volume tric texture representation). The major technical considerations of ou r method lie in the ray-path determination and in the specification of the reflectance function.