Trilinear texture filtering of two levels of detail based on a single level of detail

Abstract

A trilinear texture filtering system and method that improves the locality of texture map accesses in a multum in parvo (MIP) map so as to reduce page breaks and provide improved performance. The present invention includes a texture cache having a unique addressing and accessing scheme that allows localized reads of the texture map from each of four banks in the texture cache. This is coupled with a unique texture-mapping unit that includes a first level generator, a second level generator and an interpolator. In generating the lower-resolution texture map version, the present invention filters neighboring texels from the higher-resolution version. Thus, an n×n (e.g. 2×2) square of texels at the higher-resolution level is reduced to a single texel at the lower-resolution level. This technique permits the lower-resolution level to be derived without requiring additional read operations from texture memory with potentially poor locality. Furthermore, the generation of the lower-resolution level texel according to the present invention is performed in less time than required to retrieve the texel from memory. Interpolation can then be performed using the higher-resolution version and the derived lower-resolution version.