shadevis

VCG ShadeVis computes a simple, static (but much more correct) per-vertex ambient term. This effect, commonly known as ambient occlusion, is aimed at providing more faithful shading for realtime rendering. In practice, rather than considering the ambient lighting to exist uniformly throughout a scene, this approach determines the ambient brightness of each part of a surface to be proportional to the extent to which the surface has "its outward view of its environment" free (i.e., "occluded") by other surfaces of the object. The most common technique to compute ambient occlusion is based on shooting rays from each surface element to evaluate the quantity of light that reaches it. VCG Shadevis uses OpenGL to accelerate this process by simply rendering the scene orthographically from a set of uniformly-distributed directions and checking against the zbuffer whether each vertex is occluded.