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Re: [cgal-discuss] Overlaying Arrangement_with_history destroys edge-to-curve mapping


Chronological Thread 
  • From: Efi Fogel <>
  • To:
  • Subject: Re: [cgal-discuss] Overlaying Arrangement_with_history destroys edge-to-curve mapping
  • Date: Tue, 15 Oct 2019 23:50:53 +0300
  • Authentication-results: mail2-smtp-roc.national.inria.fr; spf=None ; spf=Pass ; spf=None
  • Ironport-phdr: 9a23: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
No and maybe.
First, one of the creation functions of edges is invoked for every edge in the overlay resulting traits.
An edge can be the result of the overlap of 2 edges, or an edge an a face.
Secondly, make sure that arrangement with history do not provide what you need.
However, they are somehow limited (and can be improved).
Using extended arrangements and a custom overlay traits is more powerful though.

The data is not preserved automatically.
If the halfedge of one arrangement extended with some class A, and the halfedge of the other arrangement extended with class B, what would you expect the resulting data to look like?
Blindly having a pair does not make much sense. Yes, you need a custom traits.
   ____  _        ____             _
  /_____/_) o    /__________  __  //
 (____ (   (    (    (_/ (_/-(-'_(/
                         _/




On Fri, 11 Oct 2019 at 19:34, gp <> wrote:
How would a custom OverlayTraits model do this? The OverlayTraits concept
doesn't seem to directly involve the internal curve-to-halfedge mapping
information specific to arrangements with history. The closest it offers are
the three create_edges methods invoked whenever elements in arrangement A
intersect elements in arrangement B. But these will not necessarily be
called for all the edges in the new arrangement. Say, for instance, that
none of the elements in A or B intersect at all; OverlayTraits will, if I
understand right, never have any input.

Should I abandon arrangements with history and imitate them by managing the
curve-handle-to-halfedge mapping manually through halfedge metadata (the
HalfedgeData of Arr_extended_dcel)? If I overlay two arrangements that have
my custom HalfedgeData values assigned to their halfedges, do the
HalfedgeData values get preserved automatically in the new arrangement or do
I need to make a custom OverlayTraits model to ensure that?   



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