Masking
Using a selection as a paint mask — how the Mask scope confines brush strokes per pixel, and how the mask persists.
Reference
- Tool
- Select
- Panel
- Tool Options
- Section
- Selection
A selection made under the Mask scope becomes a paint mask: an area that confines every subsequent brush stroke. Paint applied outside it does not land. The clip is evaluated per pixel in the dab shader, so a stroke crossing the mask edge is trimmed at the edge rather than rejected as a whole — the brush can be dragged freely across the boundary and only the inside is painted.
The mask lives on the surface it was lassoed onto, not on the screen. Orbiting the camera leaves it on that wall.
Making a mask
Reference
- Tool
- Select
- Section
- Scope ▸ Mask
Set the Select tool's Scope to Mask, then box or lasso the area. The Mode control chooses between a rectangular box and a freehand lasso, exactly as it does for the other scopes.
A tap on the canvas under this scope clears the mask.
Rubbing inside a shape makes the mask the loop that surrounds it — the same loop the bucket would fill — instead of the scribble that was drawn. The boundary is found with the fill tool's own boundary set. The probe is taken first from the region's centroid, then from where the gesture started. With this off, the drawn path itself is raycast onto the surface and becomes the mask.
Confines painting to everything outside the selected area instead of inside it.
Removes the mask. Disabled when no mask exists.
Above these controls the panel carries a read-only status line, reading "Mask active — strokes clip to it" when a mask exists and "No mask yet" when none does. The whole block is shown whenever the scope is Mask, and also whenever a mask exists under any scope — so a mask left active is visible from the panel without switching back.
The Snap grid to stroke button is hidden under the Mask scope.
Masking to a detected subject
Reference
- Tool
- Select
- Section
- Scope ▸ Smart
The Smart scope can produce a mask instead of a lifted piece. Set Smart target to Mask and tap a subject in an imported photo: the detected outline is passed to the same mask machinery, and painting is confined to the subject.
Smart requires an image under the tap. See Select tool for the detection's requirements and limits.
Persistence
The mask is not a transient screen state. When a stroke is painted under an active mask, the clip region is baked onto the stroke itself, so it survives saving and reloading: the stroke is rebuilt from its points on load and the clip is rebuilt with it. The mask does not have to be re-made to reopen the artwork correctly.
The eraser is not masked
The paint mask constrains brush strokes. The Eraser is not clipped by it and will rub out ink on either side of the mask edge.