Improved Diffuse Anisotropic Shading

Cloth, hair, brushed metal, and other surfaces with small, regular surface features exhibit anisotropic reflectance properties for which common isotropic shading methods are not suited. Shading of such materials is often implemented by computing the normal giving the maximum light contribution instead of solving the integral that is the sum of all reflected light. In this paper we show that this integral can be simplified if the direction to the viewer and fibre geometry is not taken into account. Still, this will give a more accurate result than the very rough simplification of using the maximum contribution. This computation is simple for diffuse light. However, the specular light still needs some more elaboration to work.