Layer Mask

Uses geometry on one layer as a clipping mask to trim geometry on another layer.

When to Use

• To clip geometry to a design boundary
• To apply a window/viewport mask to layout data
• To trim layers to a common outline

Options

Option	Description	Default
Mask layer	Layer containing the clipping boundary	—
Target layer	Layer to be clipped	—
Invert mask	Keep geometry outside the mask instead of inside	Off

How It Works

1. The mask layer defines a clipping region
2. Geometry on the target layer is clipped to the mask boundary
3. Geometry outside the mask is removed (or inside, if inverted)

Technical Notes

• The mask layer geometry should form closed polygons
• Multiple mask polygons are unioned before clipping
• The mask layer itself is not modified
• This is a non-destructive complement to Crop to Bounds