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Re: [cgal-discuss] Possible bug in Arrangement_on_surface_2::merge_edge (CGAL 3.4)


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  • From: Ben Supnik <>
  • To:
  • Subject: Re: [cgal-discuss] Possible bug in Arrangement_on_surface_2::merge_edge (CGAL 3.4)
  • Date: Fri, 28 Aug 2009 21:23:26 -0400

Er, slight amendment to what I wrote before...merge_edge takes an _x-monotone_ curve.

So clearly the directedness of the underlying half-edge can never change if the resulting curve passed to merge_edge has the same path as the two previous edges _and_ is x-monotone.

This requirement of the new curve being the union of the two merged-halfedge curves isn't really stated anywhere...not sure if it's intentional.

From my perspective, it is useful to be able to replace a pair of edges with a bypassed edge when I have already determined that it is topologically safe to do so.

I could insert a new edge between vertices and then remove the other two vertices, but even when insert-between-edges is proven safe, it still involves some topology checks because the structure of faces could temporarily change and change back. Merge-edge strikes me as more efficient.

cheers
ben


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