Classification of Ray-Generators in Uniform Subdivisions and Octrees for Ray Tracing

Abstract

Spatial subdivisions cause an enormous acceleration of ray tracing due to the reduction of ray-object intersections. For this purpose it is necessary to generate the sequence of ray-cells (all cells met consecutively by a given ray). A method generating this sequence will be called a ray-generator. First this paper analyses the common properties of ray-generators in order to establish a classification. Then some well-known ray- generators are described and classified, as well as some new ones. In the sequel nine different ray-generators are implemented in one single program allowing direct comparisons with the same scene. Finally, global time measurements for two scenes are given, as well as time measurements for random rays enabling the calculation of mean values for the time of initialization and determination of ray-cells.