Object-Space, Connectivity-Preserving, Shadow Computation

Known shadow algorithms can be classified as either mapping techniques or as geometric techniques. Both involve computing visibility from a viewer located at the light source, but whereas algorithms in the first category compute a texture to be mapped on the surfaces in the scene, algorithms in the second category destruct the scene geometry to build lit and unlit polygon lists. We describe in this paper an algorithm that lies in the second category, but one that is non--destructive. Namely, the algorithm we propose ensures that all connectivity in the scene remains intact and thus that adjacency information, which is important in a solid modeling environment, remains intact