Procedural Reduction Maps

Abstract

Procedural textures and image textures are commonplace in graphics today, finding uses in such places as animated movies and video games. Unlike image texture maps, procedural textures typically suffer from minification aliasing. I present a method that, given a procedural texture on a surface, automatically creates an anti-aliased version of the procedural texture. The new procedural texture maintains the original textures details, but reduces minification aliasing artifacts. This new algorithm creates an image pyramid similar to MIP-Maps to represent the texture. Whereas a MIP-Map stores per-texel color, however, my texture hierarchy stores weighted sums of reflectance functions, allowing a wider-range of effects to be anti-aliased. The stored reflectance functions are automatically selected based on an analysis of the different functions found over the surface. When the texture is viewed at close range, the original texture is used, but as the texture footprint grows, the algorithm gradually replaces the textures result with an anti-aliased one. This results in faster development time for writing procedural textures as well as higher visual fidelity and faster rendering. With the optional addition of authoring guidelines, the analysis phase can be sped up by as much as two orders of magnitude. Furthermore, I developed a method for handling pre-filtered integration of reflectance functions to anti-alias specular highlights. The normal-centric BRDF (NBRDF) allows for fast evaluation over a range of normals appearing on the surface of an object. The NBRDF is easy to implement on the GPU for real-time results and can be combined with procedural reduction maps for real-time procedural texture minification anti-aliasing.