2008

Advanced group
Noise Filtering (Speckle Reduction) Applies a median filter using neighboring
final gather rays that are shot from the same point. This parameter lets you
choose a value from a drop-down list. The options are None, Standard, High,
Very High, and Extremely High. Default=Standard.
The practical effect of increasing the Noise Filtering value is to make the scene
illumination smoother, at a cost of render time. However, increasing filtering
can also make the illumination somewhat darker.
Noise Filtering works by eliminating stray rays that are considerably brighter
than most of the rest. For example, in a situation in which most of the rays
are within 10 percent of each others’ brightness, but a few are 50 percent
brighter than the rest, using Noise Filtering will tend to disregard the latter
rays in computing the Final Gather solution.
As a result, in low-light situations, setting Noise Filtering=None can greatly
increase the overall illumination. In the following rendered image, an interior
scene, lit only by skylight entering through the window, is very dark with
Noise Filtering set to Standard (Diffuse Bounces=1).
Noise Filtering=Standard
6110 | Chapter 18 Rendering