Method, system and computer program product for multi-pass bump-mapping into an environment map

Abstract

A method, system, and computer program product are provided for multi-pass bump-mapping into an environment map. At least two passes are made through a hardware rasterizer to bump map into an environment map. In the first pass, a lighting equation is overloaded. The overloaded lighting equation represents a reflection vector of a perturbed normal at a pixel position. The reflection vector at a pixel position is then generated according to the overloaded lighting equation. In a second pass, at least one texel in an environment map is accessed based on the generated reflection vector. For example, the generated reflection vector can be used as a look-up into the environment map to access one or more texel samples. In one example implementation, a lighting equation includes a specular material vector Sm, a lighting vector L, and an ambient material vector Am. Such a lighting equation is overloaded by setting the specular material vector Sm to equal a perturbed normal vector N′, setting the lighting vector L to equal a viewing vector V at the pixel position, and setting an ambient material vector Am to equal the viewing vector V. Other terms in the lighting equation include a specular exponent n two vectors scli and acli. To overload the lighting equation, the specular component n is set to equal one, the vector scli is set to equal to {2,2,2}; and the vector acli is set to equal to {−1,−1,−1}. A single hardware rasterizer can be used. A separate reflection vector calculation is avoided. One hardware rasterizer can be used to perform processing in each pass. Two separate texture fetch units to support a reflection vector calculation are not necessarily needed.