Evaluating the Use of Proxy Geometry for RTX-based Ray Traced Diffuse Global Illumination

Abstract

Diffuse global illumination is vital for photorealistic rendering, but accurately evaluating it is computationally expensive and usually involves ray tracing. Ray tracing has often been considered prohibitively expensive for real-time rendering, but with the new RTX technology it can be done many times faster than what was previously possible. While ray tracing is now faster, ray traced diffuse global illumination is still relatively slow on GPUs, and we see the potential of improving performance on the application-level. We examine how well proxy geometry can work for RTX-based, ray traced diffuse global illumination, in terms of rendering time and visual error. Three different types of proxy geometry are tested—simplified triangle meshes, sphere sets, and voxel planes—to evaluate whether it is possible to get faster rendering without introducing significant visual error. We also identify a few requirements that such proxy geometry should fulfill. We find that it is possible to achieve faster rendering times with relatively small errors using proxy geometry. While all proxy types demonstrate different performance and error characteristics, for all evaluated scenes we find that there is a simplified triangle mesh proxy with lower errors than all other types, which is also faster to render than the reference. This cannot be said for any of the other proxy types.