A two-pass solution to the rendering equation: A synthesis of ray tracing and radiosity methods

Abstract

View-independent and view-dependent image synthesis techniques, represented by radiosity and ray tracing, respectively, are discussed. View-dependent techniques are found to have advantages for calculating the specular component of illumination and view-independent techniques for the diffuse component. Based on these observations a methodology is presented for simulating global illumination within complex environments using a two-pass approach. The first pass is view-independent and is based on the hemi-cube radiosity algorithm, with extensions to include the effects of diffuse transmission, and specular to diffuse reflection and transmission. The second pass is view-dependent and is based on an alternative to distributed ray tracing in which a z-buffer algorithm is used to sample the intensities contributing to the specularly reflected or transmitted intensity.