Abstract: We present a bump mapping method that requires minimal hardware beyond that necessary for Phong shading. We eliminate the costly per-pixel steps of reconstructing a tangent space and perturbing the erpolated normal vector by a) interpolating vectors that have been transformed into tangent space at polygon vertices and b) storing a precomputed, perturbed normal map as a texture. This represents a considerable savings in hardware or rendering speed compared to a straightforward implementation of bump mapping.