Inflate
Reference
Mode:
Sculpt Mode
Tool:
Toolbar ‣ Inflate
Shortcut:
I
Similar to Draw, except that vertices are moved in the direction of their own normals. Especially useful when sculpting meshes with a lot of curvature.
Also available as a Mesh Filter to inflate all unmasked areas at once.
Brush Settings
General
Direction
Either Inflate or Deflate sculpted areas. This is different from the typical Add & Subtract.
Note
More info at General brush settings and on Advanced brush settings.