Efficient Screenspace Rendering for Area Lights

• Main Authors: Koa, Ming Di, Johan, Henry
• Other Authors: School of Computer Science and Engineering
• Format: Conference or Workshop Item
• Language: English
• Published: 2017
• Subjects: Computer graphics; Interactive rendering
• Online Access: https://hdl.handle.net/10356/81403; http://hdl.handle.net/10220/43458
• Institution: Nanyang Technological University

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 discontinuity 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 pass screenspace irradiance up-sampling scheme which uses Gaussian radial basis functions (RBF) for interpolating scattered fragments. This reduces artifacts caused by large fragments while also significantly reducing the number of fragments that we require. Our indirect illumination is computed by distributing a set of Poisson sample points in the scene. Each LPV voxel performs a light gathering operation on these samples and deposits them internally. Light intensity in the LPV is propagated simulating indirect illumination from area lights. From experiments, our techniques are able to run at interactive rates.