Final Gathering using Ray Differentials

Christensen,N.-J., Gjol,M., Larsen,B.D.

A method of attaining better quality from the calculations of indirect illumination in photon mapping, which is used for global illumination has been developed. At the final gathering step in photon mapping, photons have previously been sampled over an area, which is determined by the distribution of photons. This strategy gives a series of problems, that are usually solved, by increasing the sampling rate. To reduce these problems I suggest sampling over the real area, given by the area the ray ought to cover. In this project I calculate the footprint by using ray differentials, and look up in a precalculated mipmap of estimated irradiance values. By doing this a better estimate of the incoming diffuse lighting is achieved, which means a more correct image with the same amount of samples. By using a mipmap of irradiance estimates this enhancement is reached faster than using regular final gathering.