A visibility sorting method coherently computes a visibility ordering of a
collection of moving objects seen by a moving camera in an animated
graphics scene. The method detects whether an object occludes other
objects. Objects that form an occlusion cycle are grouped together in the
ordering. Objects are represented using convex polyhedra to facilitate
occlusion testing. A fast occlusion test determines whether the spatial
and angular extents of the convex polyhedra overlap. An exact occlusion
test detects collisions between convex polyhedra and the silhouettes of
the convex polyhedra.