From BlenderWiki
Paint Masks
Paint masks allow you to interactively mark areas of a mesh that should be left unaffected by the brush. The mask appears as darker markings on the mesh; the darker the mask is, the more it "resists" any changes.
Paint masks work in sculpt mode and vertex paint mode, with both regular meshes and multiresolution meshes.
Usage:
- Go into sculpt mode or vertex paint mode.
- Add a mask layer (in the Masking section of the TKEY panel.)
- Click the "Mask" checkbox in the Brush section.
- Apply masking to the mesh. The mask brush mode works like any other brush, except it affects masking rather than vertex coordinates or colors. This means you can use all the stroke tools, textures, brush curve, etc.
- Switch to a regular brush and draw a stroke over the mesh. The masked off portions will resist the regular brush's changes.
Notes:
- Use the Clear/Fill/Invert buttons to change the entire mask at once.
- You can add multiple mask layers; they will have a cumulative effect on the brush.
- Individual mask layers can be toggled on or off with the checkbox to the right of the layer name.
- The strength slider decreases the effect a mask layer has on the brush.
Ptex Paint
Models can now be painted using Disney's Ptex [1] format. Details can be painted without high mesh density (unlike vertex paint), and without explicitly assigning U/V coordinates (unlike texture paint.)
Ptex paint uses the same optimizations as sculpt mode. Almost all of the brush features in sculpt mode are now available in vertex paint as well.
Ptex layers can be added via the mesh data panel. A Ptex layer can contain any number of channels (for example, four channels could be used to represent RGBA, or a single channel could be used to represent specularity.) The data type of the layer can also be set; currently 8-bit, 16-bit, and (floating-point) 32-bit are supported.
Ptex prefers to work on quad data. In order to support triangles, each triangle is split into three subfaces, each of which is a quad and can have its own independent resolution.
When a Ptex layer is added, the density of texels per face is automatically assigned. The density can be adjusted by entering the paint face selection mode. In this mode the texels are visually represented on the model as alternating colors. Multiple faces can be adjusted by selecting them and clicking "Double Selected" or "Half Selected" in order to double or half the U/V resolution of each face. Any painted data is interpolated to the new resolution. The resolution of a single face can be set more precisely with the Set Resolution button, which allows individually setting the U and V resolutions, as well as adjusting the per-subface resolution (for non-quads.)
Feedback
If you have problems with the tool or any other feedback, just post it here: http://blenderartists.org/forum/showthread.php?t=187912
Updates
Development updates here: http://twitter.com/nicholasbishop
