To freeze based on a sculpt layer

1. Ensure your model is at the same subdivision level as the sculpt layer you plan to use.
2. Right-click the sculpt layer, or open the Sculpt layer menu ( ) and select Freeze From Selected.
3. In the Freeze from Selected window that appears, set the desired Contrast and Midpoint values, then click Freeze.

   Mudbox assigns a freeze value to each vertex affected by the current sculpt layer. The levels of freezing are determined by the relative displacement of each vertex compared to the vertex with the greatest displacement, which receives maximum freezing.