Hardware Implementation of Phong Shading using Spherical Interpolation

Computer image generation systems often represent curved surfaces as a mesh of planar polygons that are shaded to restore a smooth appearance. In software rendering Phong shading has been one of the most successful algorithms, because it can realistically handle specular materials. Since it requires the rendering equation to be evaluated for each pixel, its hardware support poses problems. This paper presents a reformulation of the Phong shading algorithm that is based on interpolating on the surface of spheres. The reformulation results in simpler formulae that can be directly implemented in hardware. The software simulations and the VHDL description of the shading hardware are also presented