Improved Bump Mapping by using Quadratic Vector Interpolation

Abstract

Bump mapping is a technique that perturbs normals used in the illumination computation in order to make the surface appear rough or wrinkled. Standard graphics hardware linearly interpolates rotated vectors in the direction to the light source over the polygon. Then, a cube map is used to normalize these vectors. We propose the use of quadratic interpolation instead, which will make the normalization stage unnecessary. The result is faster bump mapping with quality near the quality obtained by using vector interpolation with normalization. Quadratic interpolation is already used for ordinary shading but has to our knowledge not previously been used for bump mapping. The fast setup we use in our new algorithm can also be applied to Phong shading resulting in increased performance. Similarly the same approach can be used for efficiently setting up the linear interpolation.