Rendering is the process of generating an image from a model. In the present article from a scene. A 3D modeled scene. A friend of mine is currently working on various rendering algorithms and introduced me to an unknown (to me) open source project called LuxRender. LuxRender (link) is an open source renderer that among other features it supports unbiased rendering.

In computer graphics, unbiased rendering refers to a rendering technique that does not introduce any systematic error, or bias, into the radiance approximation. Because of this fact, they are often used to generate the reference image by which other rendering techniques are compared to. Mathematically speaking, the expected value of the unbiased estimator will always be the correct value, for any number of samples. Error found in an unbiased rendering will be due to variance, which manifests itself as high-frequency noise in the resultant image (wikipedia).

He demonstrated me a few examples and the results were really fascinating. Many renderers support unbiased rendering but only propriety ones like the ones that are listed below:

Propriety means that you cannot be sure if you are getting the unbiased rendering you are supposed to get. I wish him luck with his new toy