GENERATEBOUNDARY command
Generates a closed polyline or spline around the boundary of a flat, closed area.
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Description
Generates a closed polyline or spline around the boundary of a planar closed area, a planar face of a 3D solid or around the area of a hatch pattern.
Method
Select a planar enclosed point to generate a boundary by picking a point inside one of the following entities:
- Closed planar area
 - Planar face on a 3D solid; to select the face of a 3D solid hold down the Ctrl key.
 - Hatch pattern
 
The resulting boundary are:
- Polyline - when the boundary is polygonal (has corners, like a square)
 - Spline - when the boundary is curved, like a spline.