Frame-to-frame coherence and the hidden surface computation: constraints for a convex world

Frame-to-frame coherence is the highly structured relationship tha t exists between successive frames of certain animation sequences. From the point of view of the hidden surface computation, this implies tha t parts of the scene will become visible or invisible in a predictable fashion. In this paper the frame-to-frame coherence constraints are identified and characterized for static scenes restricted to stationary, closed, convex, nonintersecting polyhedra. The animation derives from a continuous movement of the viewer. The mathematical analysis of the constraints is geometric and leads to a characterization of the self-occlusion or change of self-occlusion relationship over a single polyhedron, and to a characterization of the occlusion or change of occlusion relationship over two polyhedra. On the basis of these constraints, an algorithm which generates successive frames in an animation sequence is presented.