3DCoat support grayscale layer masks as in Photoshop or Substance Painter, and also uses Paint Layer Transparency to stand for what black means in regular compositing.
It will translate between Opacity/Transparency state and Freeze state.
Recently was added the ability to save a Freeze Mask to a Paint Layer (the same way you can store a POSE selection to a Paint Layer).
When the FREEZE tool is active, you will see the Options to “FREEZE to LAYER,” “CLICK & PICK to FREEZE” and “CURRENT LAYER to FREEZE”.
Freeze Menu commands
Activate Freeze Tool: Activates the Paint Room’s Freeze tool.
Toggle Freeze View: Changes the way that Frozen areas are displayed. Choose between various patterns, black or white.
Show/Hide Freeze: Turns the Freeze pattern on/off.
Freeze Painted Pixels: Freeze only pixels that have paint on them.
Freeze Transparent Pixels: Freeze only pixels that do not have paint on them.
Freeze Surface: Freezes the entire surface of the selected layer.
Freeze Border: Freezes only the border of the current Frozen area. Great for painting a selection with the intent of painting only the bordering area.
Freeze Paint Object: Freeze an entire Paint Object.
Freeze Surface Material: Freeze an entire Surface Material.
Unfreeze Paint Object: Unfreeze an entire Paint Object.
Unfreeze Surface Material: Unfreeze an entire Surface Material.
Unfreeze All: Unfreeze everything.
Invert Freeze/Selection: Inverts the Frozen area to be Unfrozen and the Unfrozen area to be Frozen.
Smooth Freezing: Smooths the Frozen area by feathering the pixels on the border.
Sharpen Freezing: Sharpens or increases the opacity of the Frozen pixels.
Fill Unfrozen: Fill an Unfrozen area with the current color and Glossiness amount.
Erase Unfrozen: Erase the Unfrozen areas.
Hide Frozen Area: Hide only the Frozen areas.
Expand Frozen Area: Expands the Frozen area by 1 pixel.
Contract Frozen Area: Contracts the Frozen area by 1 pixel.
Store Freezing State: Stores the Frozen state to disk. It can be loaded with the Freeze tool under the Tool Options panel.
Restore Freezing State:
Fill Unfrozen: Fills the Unfrozen areas.
Fill by Transparency: Fills only the transparent pixels with the current color.
Freeze Operations hotkeys
Alt+F Switch freeze view
Ctrl+F Show/hide freeze
Ctrl+NumPad / Freeze border
Ctrl+NumPad + Expand the frozen area
Ctrl+NumPad – Contract frozen area
Ctrl+D Unfreeze all
Ctrl+Shift+I Invert freeze/solution
Ctrl+NumPad * Smooth freezing