Summary
This chapter provided a detailed overview about photon rendering and thus completes the full implementation of the photon-mapping algorithm. You've developed a method to search for the closest photons around the point of intersection and will use the returned photons to average the incoming radiance for a point of interest. You can now render the scene using backward ray tracing by finding the radiance estimate of a point on a surface in the scene. Currently, the photon mapping application is very slow because you're using an array to store photons in the photon map. The render time was very long for the photon.txt render because traversing through a linear array is a very slow process. The next chapter, therefore, discusses how to increase the efficiency of searching for photons when finding the radiance estimate.