CGAL users discussion list

[Ignacio Javier Osorio Wallace <>]

Thx a lot Laurent,

So I'm reading about it. And in order to use the minimum length required 
as the stop predicate of the function. I need to:

#include 
<CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Edge_length_stop_predicate.h>

which is not being found. I wonder if I need to link other flags to the 
compiler? (I already have CGAL, CGAL_CORE and CGAL_ImageIO, and boost 
stuff).

I did follow the documentation: 
http://doc.cgal.org/latest/Surface_mesh_simplification/index.html
found how to convert the c2t3 to a polyhedron: 
http://doc.cgal.org/Manual/3.6.1/include/CGAL/IO/output_surface_facets_to_polyhedron.h
and I'm trying to make the algorithm work with the 
edge_length_stop_predicate using this example: 
https://github.com/CGAL/cgal/blob/master/Surface_mesh_simplification/examples/Surface_mesh_simplification/edge_collapse_all_short_edges.cpp

I hope I'm on the right path.
Thx a lot for the support,
best regards,
Ignacio.

El 2017-06-09 05:20, Laurent Rineau (CGAL/GeometryFactory) escribió:
> Le Thursday, June 8, 2017 8:59:46 PM CEST Ignacio Javier Osorio Wallace 
> a ?
> crit :
> > Hello CGAL community, I need a small help with a surface extraction 
> > that
> > I need to implement.
> >
> > I'm creating a surface for a finite element algorithm. And I need the
> > edges to have a minimum size restriction. I would be perfect if the SD
> > of all the edges were as small as possible.
>
> Hi,
>
> You cannot define a minimal size for edges (or triangles) when using
> `CGAL::make_surface_mesh`. If the size of edges is significantly 
> smaller than
> the size criterion given to the critera object
> (`CGAL::Surface_mesh_default_criteria_3`), then that probably means 
> that the
> geometry of the domain surface has locally a small feature size.
>
> You may try post-process the result of `CGAL::make_surface_mesh` with a
> surface simplification algorithm: export the `c2t3` object to a 
> polyhedron,
> and then use the methods from the CGAL chapter "Triangulated Surface 
> Mesh
> Simplification":
>
>   http://doc.cgal.org/4.10/Surface_mesh_simplification/index.html
>
> But the global guaranties (no self-intersection) will no longer be
> guaranteed.
>
> > Here is a the code.
> > Thx for the help, btw.
> > Best regards,
> > Ignacio.
> >
> > typedef CGAL::Simple_cartesian<double> Kernel;
> > typedef Kernel::Point_2 Point_2;
> >
> > // default triangulation for Surface_mesher
> > typedef CGAL::Surface_mesh_default_triangulation_3 Tr;
> > // c2t3
> > typedef CGAL::Complex_2_in_triangulation_3<Tr> C2t3;
> > typedef Tr::Geom_traits GT;
> >
> > typedef CGAL::Gray_level_image_3<GT::FT, GT::Point_3> 
> > Gray_level_image;
> > typedef CGAL::Implicit_surface_3<GT, Gray_level_image> Surface_3;
> >
> > Tr tr;            // 3D-Delaunay triangulation
> > C2t3 c2t3 (tr);   // 2D-complex in 3D-Delaunay triangulation
> > char *inriaFile;
> > char *outputFile;
> >
> > Gray_level_image image(inriaFile, 0.3);
> >
> > GT::Point_3 bounding_sphere_center(109,109,67);
> >
> > GT::FT bounding_sphere_squared_radius = float(218) * float(218) *
> > float(2);
> >
> > GT::Sphere_3 bounding_sphere(bounding_sphere_center,
> > bounding_sphere_squared_radius);
> >
> > Surface_3 surface(image, bounding_sphere, 0.00001);
> >
> > CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30,2,2);
> >
> > CGAL::make_surface_mesh(c2t3, surface, criteria, 
> > CGAL::Manifold_tag());
> >
> > //for(C2t3::Vertex_iterator iter(c2t3.vertices_begin()); iter !=
> > c2t3.vertices_end(); iter++ ) {
> > //std::cout << iter->point().x() << iter->point().y() << iter->point()
> > << std::endl;
> > ////Point p(iter->point());
> > //}
> >
> > std::ofstream out(outputFile);
> > CGAL::output_surface_facets_to_off (out, c2t3);
> > std::cout << c2t3.number_of_facets() << std::endl;
> >
> > std::cout << "qRx : Surface, final number of points: " <<
> > tr.number_of_vertices() << "\n";
> > std::cout << "qRx: Surface, end!!" << std::endl;
>
>
>
> --
> Laurent Rineau, PhD
> R&D Engineer at GeometryFactory           
> http://www.geometryfactory.com/
> Release Manager of the CGAL Project       http://www.cgal.org/