Indirect illumination using photon splatting

Abstract

Indirect illumination algorithms exist in many forms, but the state-of-the-art real-time algorithms often limit the rendering equation in terms of visibility determination or leave it out completely. The main focus of this thesis is to adapt the existing high quality photon mapping method in order to make the visibility determination closer to the real-time field. Similar to the splatting indirect illumination technique, our technique works by placing many indirect light sources in the scene. However, we consider these light sources as small orthographic area light sources instead of point light sources. This allows us to introduce a novel technique for visibility determination. This technique bundles light rays into a single ray for a more efficient, but still plausible, indirect illumination if many samples are averaged. The final illumination is then applied by splatting this single ray using an orthographic shadow map that serves as a local visibility determination for the entire bundle. Furthermore, we introduce a new technique for stratifying these light sources in 3D space. A highly parameterized version of this algorithm was implemented, as well as a photon mapping implementation to serve as a ground truth. Both algorithms are assessed in terms of quality, resources and speed. Our result show an improvement in rendering time with minor loss of quality, although the time required for our algorithm to converge is still far out of the real-time range. However, our techniques have been concocted keeping hardware acceleration in mind. Such implementation might show promising results.