Interactive indirect illumination using voxel cone tracing

Abstract

Indirect illumination is an important element for realistic image synthesis, but its computation is expensive and highly dependent on the complexity of the scene and of the BRDF of the surfaces involved. While off-line computation and pre-baking can be acceptable for some cases, many applications (games, simulators, etc.) require real-time or interactive approaches to evaluate indirect illumination. In this paper, we present a novel real-time solution that calculates two light bounces - either glossy or diffuse - using a hierarchical voxel representation generated from a regular scene mesh. Our algorithm consists of two steps. First, direct illumination information (energy and direction) is emitted from dynamic area light sources and splatted into the voxel hierarchy, accounting for possible occluders. Secondly, we draw the scene mesh and compute the illumination in the pixel shader by combining the direct illumination and the indirect illumination received from the rest of the scene. For the latter, our approach employs an approximate voxel cone tracing to efficiently collect visibility and light in the hierarchical voxel representation of the scene. Our solution offers real-time and almost geometry-independent performance with a high visual quality for complex scenes with diffuse, as well as glossy surfaces.