Gather Indirect Lighting method
There are two methods for Indirect Lighting - Standard and Gather.
Gather sometimes produces a smoother effect, but takes longer.
Gather Indirect Light uses Monte Carlo like techniques to solve the indirect portion of the lighting. Images start out noisy and gradually refine. May be useful for exterior daylighting-- much slower for interiors than standard method and not much better.
This image after just one pass may help you understand what Gather Lighting does:
(You can see how reflected light is moved into the dark area more quickly.)
- [Indirect_Lighting#Indirect_Lighting_Methods|Indirect Lighting]