CGAL users discussion list

[paulo <>]

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

Laurent Saboret wrote:
> Hi Paulo,
>
> The first step to use CGAL surface mesh parameterization is to convert 
> your data to CGAL Polyhedron_3 
> http://www.cgal.org/Manual/last/doc_html/cgal_manual/Polyhedron/Chapter_main.html 
>
>
> You have several ways :
> * Save your data in a .OFF file and let Polyhedron_3 read it (the 
> easiest) 
> http://www.cgal.org/Manual/last/doc_html/cgal_manual/Polyhedron/Chapter_main.html#Section_23.4 
>
> * Convert your data by code (as you started below) using Euler 
> operations 
> http://www.cgal.org/Manual/last/doc_html/cgal_manual/Polyhedron/Chapter_main.html#Subsection_23.3.7 
>
> * Convert your data by code using Polyhedron_incremental_builder_3 
> http://www.cgal.org/Manual/last/doc_html/cgal_manual/Polyhedron/Chapter_main.html#Subsection_23.6.2 
>
>
> Best regards,
> Laurent Saboret
>
>
>
>  wrote:
> > Hello,
> >
> > I'm using CGAL's parameterization package.
> > There's a very nice page explaining how to use if with OFF files, but 
> > that's
> > not my case.
> > So, instead of loading a mesh from a file, I'm trying to pass my 
> > vertices and
> > faces to CGAL.
> >
> > My data is formatted in a opengl typical pattern. I have a vertex 
> > array, one or
> > more arrays of triangular faces. These faces contain no more than 
> > indexes to
> > the vertex array.
> >
> > What I'm doing is to pass the face like:
> > typedef CGAL::... Poly;
> > Poly poly;
> > for all my faces     get the face vertexes (pa, pb and pc)
> >     poly.make_triangle(Point(pa.x, pa.y, pa.z), Point(pb.x, pb.y, pb.z),
> > Point(pc.x, pc.y, pc.z));
> >
> > Of course this repeats vertexes (points), and does not give any 
> > information
> > about the faces connectivity.
> > In the end, running the algorithm I get: "Parameterization requires a 
> > convex
> > border"
> > The mesh I'm using right now is just a couple of coplanar triangles, 
> > or if you
> > want, a tessellated unit square.
> >
> > But I can't seem to be able to find how to pass the vertexes and the 
> > faces
> > separately.
> > Nor do I know how to specify the border.
> > Is there an example of this somewhere?
> > I am searching the examples and demos, but some help would be greatly
> > appreciated.
> >
> > Thank you
> > Paulo
> >
> >