CGAL users discussion list

[Stefan Salewski <>]

On Mon, 2013-09-30 at 10:04 -0500, John Griessen wrote:
> On 09/30/2013 09:20 AM, Stefan Salewski wrote:
> >> these are the edges adjacent to two marked polygons
> > For my case I may have only one polygon (or more than one but with large
> > distance to each other). I want to find the inner edges,
> 
> The triangles are polygons that are adjacent, have adjacent edges, and are
> always convex.  That lets you find inner edges if all are marked as being 
> part of
> a larger non-convex polygon and whether they are part of a particular 
> triangle.
> 
> For triangles that are a subset of the larger non-convex polygon:
> If a triangle edge is part of a triangle and also part of an adjacent 
> triangle,
> then it is interior.
> 
> You can mark "part of" or "outside of" the larger non-convex polygon
> as you go, right?  It is what you start with, then create Delaunay 
> triangles from, right?
> 

Thanks, now I understand the idea!
For the implementation I may still have some problems, because my
triangulation is currently vertex-based
(http://www.ssalewski.de/CDT.html.en) based on some CGAL example code,
and indeed vertex-based makes sense for my application, because my main
task is iterating over all vertices in the triangulation and finding all
neighbor vertices. I have to investigate if I am able to label faces in
an vertex-based constrained delaunay triangulation.

But fortunately my constrained polygons are convex, so I always can used
the simpler solution.

Thanks,

Stefan Salewski