A cost-effective VLSI architecture for anisotropic texture filtering in limited memory bandwidth

Abstract

Texture mapping is one of the techniques that express realism in three-dimensional (3-D) graphics. To produce high-quality images, various anisotropic filtering methods have been proposed for texture mapping. These methods require more texels than isotropic (trilinear) filtering method. In spite of increases to texture memory bandwidth, however, texture memory bandwidth is still a bottleneck of texture-filtering hardware. Consequently, an exact filtering method is required for good-quality images in a limited texture memory bandwidth. In this paper, we propose anisotropic texture filtering based on edge functions. Our method proposes an exact footprint-shape approximation with edge functions for generating weights. For real-time filtering, the weight plays a key role in effective filtering of the restricted texels loaded from memory. The normalized value of the edge function gives the distance relative to the contribution of texels to a final intensity. Calculating a Gaussian filter using this normalized value, generates a good weight. The quality of rendered images is superior to other anisotropic filtering methods with the same restricted number of texels. For images of the same quality, our method requires less than half the texels of other methods. Consequently, the improvement in performance is more than twice that of other methods. With low hardware overheads, our method can be implemented at a reasonable cost. In practice, the algorithm is demonstrated through VLSI implementation. The hardware, which is described by verilog and synthesized with a 0.35-mu m 3.3-V standard cell library, is operated at 100 MHz and it generates 100 M texture-filtered RGB pixel-color values per second.