`Brush` has two attributes for holding texture information (`MTex`).
One for color textures (`mtex`) and one for mask textures (`mask_mtex`).
Unfortunately sculpt mode due to reasons used `mtex` to store mask textures.
Changes like brush asset/paint mode require modes/tools to read the mask/color texture from
one place.
To start sanatizing this we isolate the attributes in functions.
`BKE_brush_color_texture_get` and `BKE_brush_mask_texture_get`. All object
paint modes should use these functions.
This is the conventional way of dealing with unused arguments in C++,
since it works on all compilers.
Regex find and replace: `UNUSED\((\w+)\)` -> `/*$1*/`
Add new cavity automasking mode based on local mesh
curvature. Cavity masking is a great way to quickly add
detail in crevices and the like. It's meant to be used
with the Paint brush in color attribute mode. It does
work with other brushes but the results can be unpredictable.
{F13131497}
The old "dirty mask" operator has been replace with a new
"mask from cavity" operator that shares the same code with
cavity automasking.
Differences from the sculpt-dev implementation:
* It uses the word "cavity." When I first implemented
this I wasn't aware
this feature existed in other software (and other
paint modes in Blender),
and for reasons that escape me today I initially
decided to call it a concave or
concavity mask.
* The cavity factor works a bit differently. It's
no longer non-linear and functions as a simple
scale around 0.5f.
* Supports custom curves.
* Supports blurring.
Reviewed By: Julian Kaspar, Jeroen Bakker and Campbell Barton
Differential Revision: https://developer.blender.org/D15122
Ref D15122
This value was used to close gaps, but now with the new system is not needed.
Internally, still we need to keep a small leak size, but after doing a lot of test a
value of 3 is perfect, so it's harcoded.
This new option converts the stroke to outline perimeter as soon as is drawn.
If no alternative material is set, the actual material is used.
The algorithm is similar to the new operator in D15664
Reviewed By: pepeland
Differential Revision: https://developer.blender.org/D15738
