Kerkythea Rendering Software

[micheus]

A problem that we can face in many biased renders is the presence of blotches like this:

In the Kerkythea Rendering System FAQ we can find some information/tip about it:

Q. What are the pros and cons of the biased versus unbiased techniques?
Biased techniques are usually much faster, because the estimation happens sporadically and a large part of the image is usually interpolated between these key points. This might lead though to disturbing artifacts known as blotches.
Unbiased techniques on the other hand take much longer but they are
guaranteed to solve accurately for all light interactions. The artifacts in their case appear in the form of noise that is decreased over running time.

Q. I have clouds/blotches in my final image. How can I eliminate them?
If you have some kind of soft clouds or blotches, then increase the Rays in Final Gathering. Increasing the number of Rays ensures that the estimation at each gathering point is more accurate and thus, the blotchy “waving” is reduced.

Q. Any other suggestion how to further avoid blotches in photon mapping or fireflies (white dots) appearing in unbiased renders?
We have observed that a big number of blotches/fireflies comes from the material reflectance description itself. If energy conservation is not kept in reflectance description, this results in an unrealistic material that reflects more light than it receives and it “sends” blotches/fireflies to your objects in the scene.
Being more careful in materials description (in the simple non-textured case, the color weights of your various components like diffuse, specular, etc. should sum less than 1) will not only reduce/eliminate blotches but also result in a more realistic render.