CGAL users discussion list

[Olivier Devillers <>]

 a écrit :
> Hello,
> I would like to know what is the most efficient way to explore all edges of 
> all
> cells neighbor to a vertex v in a triangulation_3. Currently, I put incident
> vertices of v into a vector ( by:
> T.incident_vertices(v,back_inserter(neighbour_vertices)) ), I add v to the
> vector, and I check all pairs of vertices in this vector to see if they are
> connected by an edge in the triangulation or not( by: T.is_edge(...) ), I
> wonder if there is any more efficient way to to it?
> I would appreciate any help,
> Ehsan Aganj
>   
from

http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Triangulation_3_ref/Class_Triangulation_3.html

you have

template <class OutputIterator>
OutputIterator     t.incident_cells ( Vertex_handle v, OutputIterator cells)
       Copies the Cell_handles of all cells incident to v to the output 
iterator cells. If t.dimension() <3, then do nothing. Returns the 
resulting output iterator.
Precondition:     v Vertex_handle(), t.is_vertex(v).

template <class OutputIterator>
OutputIterator     t.incident_facets ( Vertex_handle v, OutputIterator 
facets)
       Copies the Facets incident to v to the output iterator facets. 
Returns the resulting output iterator.
Precondition:     t.dimension() =3, v Vertex_handle(), t.is_vertex(v).

template <class OutputIterator>
OutputIterator     t.incident_vertices ( Vertex_handle v, OutputIterator 
vertices)
       Copies the Vertex_handles of all vertices incident to v to the 
output iterator vertices. If t.dimension() <2, then do nothing. Returns 
the resulting output iterator.
Precondition:     v Vertex_handle(), t.is_vertex(v).


it seems that t.incident_edges is missing, (and is not what you want)
a better workarround than yours is to take incident cells and take all 6 
edges
of these cells. In that way
- an edge from v is obtained several time (6 on average)
- an edge not containing v is obtained twice (probably with both 
orientations if you do it carefully).

removing duplicates is then needed.....