Interactive global illumination based on coherent surface shadow maps

Interactive rendering of global illumination effects is a challenging problem. While precomputed radiance transfer (PRT) is able to render such effects in real time the geometry is generally assumed static. This work proposes to replace the precomputed lighting response used in PRT by precomputed depth. Precomputing depth has the same cost as precomputing visibility, but allows visibility tests for moving objects at runtime using simple shadow mapping. For this purpose, a compression scheme for a high number of coherent surface shadow maps (CSSMs) covering the entire scene surface is developed. CSSMs allow visibility tests between all surface points against all points in the scene. We demonstrate the effectiveness of CSSM-based visibility using a novel combination of the lightcuts algorithm and hierarchical radiosity, which can be efficiently implemented on the GPU. We demonstrate interactive n-bounce diffuse global illumination, with a final glossy bounce and many high frequency effects: general BRDFs, texture and normal maps, and local or distant lighting of arbitrary shape and distribution – all evaluated per-pixel. Furthermore, all parameters can vary freely over time – the only requirement is rigid geometry.