CGAL users discussion list

["Laurent Rineau (CGAL/GeometryFactory)" <>]

On Wednesday, October 17, 2018 12:06:15 PM CEST ecu wrote:
> Hi there,
> 
> After meshing (either with Constrained_Delaunay_triangulation_2 or
> Constrained_triangulation_plus_2) I would like to be able to determine which
> constraint an edge originated from, if any, but as yet have not been able
> to see how.
> 
> I know how to test if an edge is constrained in general, but not due to
> which one.
> 
> I have also noticed the insert_constraint method of
> Constrained_triangulation_plus_2 returns a Constraint_id, but I can't see
> how get this id from an edge.

You can use the function `Context context(Vertex_handle, Vertex_handle)` to 
get the information.

    Edge e;
    const Vertex_handle va = e.first->vertex(e.second);
    const Vertex_handle vb = e.first->vertex(e.third);
    const Context context = tr.context(va, vb);
    const Constraint_id id = context.id();

See the documentation:
https://doc.cgal.org/4.13/Triangulation_2/classCGAL_1_1Constrained__triangulation__plus__2.html#a65c0a285ac0f81aa246e0a06ea07ae99


-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/