Implementing an anisotropic texture filter

Texture mapping is an important operation in high-quality computer graphics applications. The principles of image filtering are well established and understood and several high-quality texture filtering algorithms have been developed. However, these have tended to be either off-line software implementations or based on high-end computer graphics rendering systems. Current generation PC-based graphics acceleration utilises texture pre-filtering techniques based upon an isotropic filter kernel. The most common implementations are those based on MIP-map texture storage and bilinear or trilinear interpolation. Such filters give a reduction in image aliasing at the expense of introducing blurring. As acceleration hardware performance improves, tolerance of such compromises is falling leading to the adoption of "anisotropic" filtering solutions. In this paper we present a detailed description of a low-cost implementation of an anisotropic filtering unit for use within a contemporary graphics pipeline. The filter is shown to produce improved visible results for only a modest increase in hardware cost. (C) 2000 Elsevier Science Ltd. All rights reserved.