* Add new color grading feature: shadows/mid-tones/highlights
This feature can be used to color correct specific tonal ranges.
The tonal zones can be precisely controlled.
* Add the ability to set a ColorGrading LUT per View
In this change, material_sandbox allows to change the tone mapping
operator at runtime.
* Add Mathematica notebook used to explore white balance
The implementation is meant to reproduce the temperature/tint sliders
founds in Adobe Lightroom. The temperature can be offset from 2,000K
to 50,000K using a slider between -100 and +100 (-1.0 to 1.0 in our
API). The range of tint was modelled after the range used for the
temperature.
* Fix various issues
- A refactoring wrongly remamed the color grading pass
- Setting a View's ColorGrading to null selects the
default color grading options
* Implement white balance in ColorGrading
We were conflating two concepts in our comments about the roughness
remapping, which was confusing. Also changed the remapping so it
matches a log2 mapping in our default configuration.
By removing the Fresnel term (often ommitted from fabric/cloth BRDFs)
we can store the DG term for the cloth BRDF in the 3rd channel of the
existing DFG LUT.
* Add new Cloth NDF
Based on the work by Estevez and Kulla, also known as the "Charlie" sheen.
* Restore DFG computation to GGX
* New proposed approximation for Cloth DFG
* Add "Charlie" cloth DFG approximation to cmgen
* Switch to "Charlie" sheen for cloth shading
* Document the new cloth NDF and DFG approximation
