Faster Photon Map Global Illumination [chapter]

Per Christensen
2005 Graphics Tools---The jgt Editors' Choice  
The photon map method is an extension of ray tracing that makes it able to efficiently compute caustics and soft indirect illumination on surfaces and in participating media. This paper describes a method to further speed up the computation of soft indirect illumination (diffuse-diffuse light transport such as color bleeding) on surfaces. The speedup is based on the observation that the many look-ups in the global photon map during final gathering can be simplified by precomputing local
more » ... ce values at the photon positions. Our tests indicate that the calculation of soft indirect illumination during rendering, which is the most time-consuming part, can be sped up by a factor of 5-7 in typical scenes at the expense of 1) a precomputation that takes about 2%-5% of the time saved during rendering and 2) a 28% increase of memory use. Background: The Photon Map Method The photon map method [Jensen 95, Jensen 96a, Jensen 96b, Jensen 96c] has the following desirable properties for computation of global illumination: 1. It can handle all combinations of specular, glossy, and diffuse reflection and transmission (including caustics). 2. Since the photon map is independent of surface representation, the method can handle very complex scenes, instanced geometry, and implicit and procedural geometry. 3. It is relatively fast. 4. It is simple to parallelize. The photon map method consists of three steps: photon tracing, photon map sorting, and rendering.
doi:10.1201/b10628-30 fatcat:giwp4rgqrnfllax34jxk54xmse