Cycles - low light threshold
Low light threshold is a function that will block sampling of a lamp if its possible contribution is below a user-defined threshold. This improves render speed (or reduces noise, when sampling a single light at a time) by focusing only on lights that significantly illuminate the current shading point.This is especially useful is scenes like tunnels, night streets, warehouses, hangers, etc, where there are a large number of light sources but only a few significantly illuminate any one particular point.There is an existing, unfinished patch for this here: developer.blender.org/D832
3 Comments
Is this a node that a user adds to the Cycles material for emitted objects or is it a global scene setting?
Probably a scene setting (in the linked patch, it appears to be a global setting alongside filter glossy and the like). It might be possible as a material node as well? Not sure on that one, I believe Mental Ray has something like this as part of the physical-light node.
Would this also be applicable for lamp distance? I mean since power decreases inverse square, after X distance every light has a contribute near to 0. So this "light-cut" should be work there too.