A GPU-based light hierarchy for real-time approximate illumination

Illumination rendering, including environment lighting, indirect illumination, and subsurface scattering, plays an important role in many graphics applications such as games and VR systems. However, it is difficult to run in real-time due to its highly computational cost. We introduce a GPU-based light hierarchy for real-time approximation of the illumination. We store virtual point lights in images and then build the view-independent hierarchy of the lights into image pyramids, with a simple and rapid clustering strategy. We approximate the illumination with small numbers of groups of lights instead of large numbers of individual lights, using a new tree traversal algorithm on programmable graphics hardware. Although we implemented our method without occlusion, we obtained visually good results in many cases. Entire steps run on programmable graphics hardware in real-time without any preprocessing.