does randomized sampling related to these advanced algorithms?
@anonymous Yes, to get extremely realistic illumination you typically have to resort to random sampling, in order to approximate difficult integrals. But even beyond what we've done here, there are very simple models for illumination that we could add to the pipeline to get more realistic appearance, such as attenuating brightness according to Lambert's cosine law (a.k.a. "N dot L" lighting), or faking things like the reflection of a bright light source using something called Phong shading. These simple models do not require random sampling.