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17. Box Cutter

A cutter is a box that cuts a hole in the object you paint, without touching your model.

Press + on the Cutters row at the bottom of Object Sets, then choose the set it should cut. Move or reshape the box and the cut follows. It affects the generated paint object, your source meshes stay untouched.

Use it to paint the inside of a closed shape, to reach a cavity the brush cannot see, to read wall thickness, or simply to get a piece of geometry out of the way for a while.

The workflow

  1. Build the object set (chapter 16.2) — a cutter needs generated objects to cut.
  2. Press + on the Cutters row.
  3. Open the target dropdown on the cutter's row (it reads --- at first) and pick the set. The Booleans appear at once.
  4. Press the cutter's name button to select it in the viewport, then move, rotate, scale or edit it like any other mesh — nothing about it is special except the name.
  5. Press the back arrow on its row to return to the object you were on before you picked the cutter.

The row:

Button What it does
back arrow re-select the object that was active before you last picked a cutter (greyed out until there is one)
rename rename the cutter; its Boolean modifiers are rebuilt under the new name
the cutter name select it in the viewport, and re-apply its Booleans if any went missing
target dropdown which object set it cuts, or --- None --- to park it
X delete the cutter and every Boolean modifier it created

Worth knowing

  • Rebuilds keep the cut. After every object-set build Overpaint re-applies the cutters that target the set, including onto the split objects in Per Material mode.

  • Procedural masks see the cut. Moving or changing a cutter updates the helper-map bakes on the objects it cuts.

  • Isolate includes them. Isolating a set brings the cutters aimed at it into local view, so you can keep adjusting them in there.

  • The prefix is the marker. Overpaint finds cutters by the _CUTTER. prefix. Rename one to anything else and it disappears from the list while its Boolean modifiers keep cutting, with no row left to remove them — keep the prefix.
  • Park them before the final bake. A cutter is still cutting when the exporter bakes: the Boolean travels with the copy the exporter makes, so cut-away faces bake as empty texels. Set the dropdown to --- None ---, or delete the cutter, before an export you intend to ship.