SPAF: Sub-texel Precision Anisotropic Filtering

Abstract

Texture mapping is a technique which most effectively improves the realism of computer-generated scenes in 3D Graphics. Trilinear filtering of the mip-mapped textue has been popular as a texture filtering method but it blurs images on the surface of objects angled obliquely away from the viewer in a scene. Various anisotropic filtering methods like footprint assembly, Feline, and fast footprint mip-mapping have been proposed to satisfy the desire for the high quality image [7]. In spite of the increase of the memory bandwidth, tie memory bandwidth limit is still the bottleneck of the texture filtering hardware. Moreover, it is very important to keep the quality of rendered image good. In this paper, we propose Sub-texel Precision Anisonopic Filtering (SPAF) which filters texels in a region that covers a quadrilateral footprint with the weights. The weight plays a key role in effective filtering to render the image of high quality with the restricted number of texels loaded from memory for real-time filtering. First, the area coverage based texel filtering scheme is introduced to obtain the footprint's coverage for each texel on the sub-texel precision leading to the small weight table size. Second, the Gaussian weight is applied to this footprinfs coverage for each texel to reduce the artifacts. Therefore, the quality of rendered images is superior to other anisotropic filtering methods in the same restricted number of texels. And the size ofthis weight table is several hundred KBytes which is much smaller than fast footprint mip-mapping. This small ROM table size enables the SPAF to be implemented at feasible hardware costs.