Efficient screenspace rendering for area lights

Efficient rendering of illumination from area lights in virtual scenes has always proved to be challenging. We extend the work of multi resolution rendering and Light Propagation Volumes (LPV) to simulate direct and indirect illumination from area lights respectively. To compute direct illumination, we create 2D multi resolution fragments to represent the scene on the screenspace, in which higher resolution fragments are created when normal, depth and visibility dis-continuity are found. Our subdivision scheme performs a sub-fragment visibility test (SFVT) within each fragment and our proposed gradient aware screenspace subdivision (GASS) algorithm accelerates the refinement by increasing the number of subdivisions based on gradient differences. We also propose a single pab screenspace irradiance up-sampling scheme which uses Gaubian radial basis functions (RBF) for interpolating scattered fragments.