Approximate Visibility Grids for Interactive Indirect Illumination

The computation of indirect illumination is fundamental to simulate lighting within a virtual scene correctly and is critical when creating interactive applications, such as games for serious applications. The computation of such illumination is typically prohibitive for interactive or real-time performance if the visibility aspect of the indirect illumination is to be maintained. This paper presents a global illumination system which uses a structure termed the Approximate Visibility Grid (AVG) which enables interactive frame rates for multiple bounce indirect illumination for fully dynamic scenes on the GPU. The AVG is constructed each frame by making efficient use of the rasterisation pipeline. The AVG is then used to compute the visibility aspects of the light transport. We show how the AVG is used to traverse virtual point light sources in the context of instant radiosity, and demonstrate how our novel method enables interactive rendering of virtual scenes that require indirect illumination.