CGAL users discussion list

[Monique Teillaud <>]

Dennis Endt wrote:
> Hi,
>
> thanks for your reply.
>
> That`s what I`m looking for:
> Segment     t.segment ( Face_handle f, int i)
>
> But this doesn`t exist.

right

> So plz tell me how can I get the edges/segments of a face where the face
> should be a triangle? A small example woulb be very nice.

If you look at the _user manual_ as previously proposed, you will easily 
understand from the text and the figure that the vertices of the facet 
(c,i) are c->vertex(i+1), c->vertex(i+2), c->vertex(i+3) [more 
precisely, all indices taken modulo 4 of course], from which you can 
access ->point()
An edge consists of two of these 3 vertices/points, as usual in a triangle.
You may want to take care of the orientation of the facet, then have 
another look at the same place in the user manual.

I think you now have all the elements, and even more, both from the 
manual and additionally from all the answers given previously on this list.

If you are expecting to get complete pieces of code ready to solve each 
step of your project, I am not sure this list is the best place.
Let me mention that the Geometry Factory company can work on providing 
customized developments for its customers, so, signing a contract with 
it could be more adapted to your needs.
There is a link from the CGAL web site to the company web site but it 
probably helps if I write it again here
http://www.geometryfactory.com/

best
        Monique Teillaud

> Olivier Devillers schrieb:
> > Dennis Endt a écrit :
> > > Hi Andreas,
> > >
> > > I read the manual for another time and it became clear how I can get a
> > > triangle of a facet. I think I understand how you define the geometry
> > > and how I can work with them.
> > >
> > > But I miss the edges of a triangle. Can I only read out the points?
> > >   
> > It must be clear that you do not "read the triangle" from the
> > triangulation.
> > The triangle you get is constructed on the fly when you ask for it.
> >
> > From the manual I get  (but you said that you looked at it ;-)
> >
> >
> > Triangle     t.triangle ( Face_handle f)     Returns the triangle
> > formed by the three vertices of f.
> > Precondition:     The face is finite.
> > Segment     t.segment ( Face_handle f, int i)     Returns the line
> > segment formed by the vertices ccw(i) and cw(i) of face f.
> > Precondition:     0 i 2. The vertices ccw(i) and cw(i) of f are finite.
> > Segment     t.segment ( Edge e)     Returns the line segment
> > corresponding to edge e.
> > Precondition:     e is a finite edge
> > Segment     t.segment ( Edge_circulator ec)     Returns the line
> > segment corresponding to edge *ec.
> > Precondition:     *ec is a finite edge.
> > Segment     t.segment ( Edge_iterator ei)     Returns the line segment
> > corresponding to edge *ei.
> > Precondition:     *ei is a finite edge.
> > Point     t.circumcenter ( Face_handle f)     Compute the circumcenter
> > of the face pointed to by f. This function is available only if the
> > corresponding function is provided in the geometric traits.
> >
> >
> > thus you can get Segment corresponding to an edge (but this segment is
> > constructed when you ask for it)
> > The only geometry stored in the trainagulation is a point for each
> > finite vertex