title: Chem-Ray: a molecular graphics program featuring an umbra and penumbra shadowing routine.
abstract: Chem-Ray, new molecular graphics program, utilizes a combination of standard algorithms developed for molecular systems as well as various ray casting techniques to produce highly realistic images on inexpensive raster terminals. The program produces images of space-filling, ball and stick or stick models derived from a user-supplied coordinate list. The most notable new feature of Chem-Ray is a simple, yet effective, algorithm for the improved treatment of shadows within a molecule. This new algorithm is based upon a calculation of a light pyramid at each point under examination. Intersections of various objects with this light pyramid will decrease the percentage of the light that can reach the point. If the entire cross-section is blocked, the point will be in the umbra of the shadow; if only a portion of the light is blocked, the point will be in the penumbra of the shadow.
authors: Department of Chemistry, State University of New York, Stony Brook 11794-3400.
authors: J W
authors: JW
authors: Lauher
mesh_terms: D000465:Algorithms; D003196:Computer Graphics; D008027:Light; D008958:Models, Molecular; D012984:Software