Some regularization problems in ray tracing
John Amanatides, Don P. Mitchell · 1990
Ray tracers that render CSG models should consider issues of regularization and numerical accuracy. The special case of rays originating on surfaces (shadow probes, reflections, and refractions) present a regular-ization problem that is significant—even in ray tracers which are not explicitly based on the CSG scheme. An analysis of this problem yields a better solution than the epsilon tests incorporated in most ray tracers. 2.