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Abstract

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.