CGAL users discussion list

[paulo <>]

Ok,
I found a temporary (?) solution.
I just need to build my faces clockwise. Ex:
 c
/  \
a - b
Face f(a,b,c) //I have ccw

//but must copy in cw order.
inc_builder.begin_facet();
inc_builder.add_vertex_to_facet(f.c);
inc_builder.add_vertex_to_facet(f.b);
inc_builder.add_vertex_to_facet(f.a);
inc_builder.end_facet();

This seems to work for the examples that I've tried untill now...
But does it make sense?

Cheers
Paulo

paulo wrote:
> Hi,
>
> after debugging CGAL's code, there's something I don't understand, and 
> looks like a bug.
>
> In the square border parameterizer it computes the offsets 0, 1, 2 and 
> 3 using the border iterator, which iterates through the vertices 
> apparently in a clockwise way, which in my case yields the sequence 
> ((-1, -1, 0) , (-1,  1, 0) , ( 1,  1, 0) ,( 1, -1, 0)).
> But afterwards it parameterizes the mesh in a counterclockwise way 
> (?!) which yields ((-1, -1, 0), ( 1, -1, 0), ( 1,  1, 0), (-1,  1, 0)).
> This does not make sense to me.
>
> But if it is a bug how come no one found it before? No one uses this 
> code?
>
> Can any one related to this implementation say something please?
> I feal tempted to change the code, but I would like to hear what other 
> people have to say.
>
> Thank you.
> Paulo
>
>
> paulo wrote:
> > Hi Laurent,
> >
> > thank you so much for your help.
> > I could only test it today, and it helped allot.
> >
> > I'm still debugging, but I'm getting a strange (in my opinion) result.
> > I'm inputing (in this sequence):
> > vertices:
> > (-1, -1, 0)
> > ( 1, -1, 0)
> > ( 1,  1, 0)
> > (-1,  1, 0)
> > Faces:
> > (0,1,2)
> > (0,2,3)
> >
> > I get a parameterization:
> > (0,0)
> > (0,1) !?
> > (1,1)
> > (1,0) !?
> >
> > This flips two of the vertices.
> >
> > Shouldn't it be:
> > (0,0)
> > (1,0)
> > (1,1)
> > (0,1)
> >
> > Am I understanding something wrong?
> >
> > Thank you.
> >
> > Best regards,
> > Paulo