Adaptive Sampling of Area Light Sources in Ray Tracing Including Diffuse Interreflection

Abstract

Ray tracing algorithms that sample both the light received directly from light sources and the light received indirectly by diffuse reflection from other patches, can accurately render the global illumination in a scene and can display complex scenes with accurate shadowing. A drawback of these algorithms, however, is the high cost for sampling the direct light which is done by shadow ray testing. Although several strategies are available to reduce the number of shadow rays, still a large number of rays will be needed, in particular to sample large area light sources. An adaptive sampling strategy is proposed that reduces the number of shadow rays by using statistical information from the sampling process and by applying information from a radiosity preprocessing. A further reduction in shadow rays is obtained by applying shadow pattern coherence, i.e. reusing the adaptive sampling pattern for neighboring sampling points.

Lightcuts

“…Final gather stages are often used to improve image quality. The methods of [Kok and Jansen 1992] and [Scheel et al 2001;Scheel et al 2002] accelerate final gathers by trying to interpolate when possible and only shooting shadow rays when necessary. While very similar in goals to reconstruction cuts, they use heuristics based on data in a radiosity link structure.…”

Grid Based Final Gather for Radiosity on Complex Clustered Scenes

“…Despite the fact that high quality images from radiosity solutions usually require a further Final Gather pass, the number of publications on this topic is relatively small. A first resampling approach based on a non‐hierarchical radiosity solution has been described in 11 . In the context of hierarchical radiosity, Final Gather was first described in 12 (called `local pass'), and shortly after in 20 .…”