Erase polygons

An erase polygon is like a clip polygon. The only difference is that instead of trimming the edges of the zone of interpolation, it cuts a hole in it.

Top: The light blue polygon will be added as an erase polygon. Middle: The polygon area is cut out of the TIN (excluded from the zone of interpolation). Bottom: As with a clip polygon, the uninterpolated area is still triangulated. The erase polygon sides become triangle edges.