CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

Le vendredi 06 janvier 2012 14:02:26 Winnie Hellmann a écrit :
> Dear list,
> 
> I am trying to find all vertices and edges of a triangulation
> (Constrained_Delaunay_triangulation_2) that intersect with an vertical
> upward ray with given x-coordinate. My first approach was to use the
> Triangulation_line_face_circulator_2, which fails in case the ray is
> collinear to a vertical edge on the left side of the triangulation's
> convex hull (see [1] and [2], and alo l2 in [3]).

In the case of l2 in [3], you could reverse the ray direction, to be in the 
case l4, and use the circulator backward.

> [1] http://www.winniehell.de/tmp/cgal/input.svg
> [2] http://www.winniehell.de/tmp/cgal/triangulation.svg
> [3]
> http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_2_ref/C
> lass_Triangulation_2.html#Triangulation_ref_Fig_Line_face_circulator

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