Efficient shading of indirect illumination applying reflective shadow maps

While global illumination is a crucial issue for most computer graphics applications fostering photo realistic rendering, fast and efficient implementations remain challenging for real-time applications. One approach to approximate indirect illumination is to distribute virtual point lights (VPL) at surfaces that emit indirect light. This distribution may be realized using reflective shadow maps (RSM). One major drawback of this approach is that each surface point has to be illuminated by thousands of VPLs, leading to a performance bottleneck in the shading step. Therefore several approaches trying to reduce the shading costs either by decreasing the number of VPLs or by lowering the surface points to be shaded exist. In our approach we propose a novel indirect shading approximation allowing us to reduce the number of surface points to be shaded to a minimum, still achieving a high image quality. Even complex and animated models can thus be represented by a few dozens of surface points for shading. Furthermore our approach allows graphic artists to intuitively tune the shading by adding or changing surface points without any pre-computations. The approach is very efficient and is completely implemented on the GPU not requiring any high shader profiles. This will even enable almost photo realistic rendering on upcoming handheld devices.