CGAL users discussion list

[Ricardo Uribe Lobello <>]

On 13/04/2011 09:14, Laurent Rineau (GeometryFactory) wrote:
> Le lundi 11 avril 2011 13:57:11, Ricardo Uribe Lobello a écrit :
> > Good morning,
> >
> > I am trying to use the Surface_mesher examples in CGAL 3.7 in order to
> > extract an surface from
> > a set of images in format raw. I used the CGALIO program to generate a
> > file .inr and i execute the
> > Surface_mesher but i always obtain only one part of the volume.
> > Apparently it has to do with the parameters of the sphere that has to
> > enclose the object and the
> > Surface_mesh_default_criteria_3 trait.
> >
> > The volume dimentions are 1024 x 1024 x 1024 and the spacing is (1,2,1).
> > The origin is (0,0,0) someone can explain me which are the good
> > parameters for the surface_mesher in this case?
> Use (512, 1024, 512) as the center of the sphere, and
>    r2 = 512^2+1024^2+512^2+1 = 1572865
> as squared radius of the sphere.

Hello,

I have tried with the parameters that you gave me but i got the same 
result, only one part
of the volume is meshed. I include the code of the main that i am using. 
This is simply a modification
of the Surface_mesher example. I have already generated surfaces using 
this code as template over
other volumes. Could someone take a look at it?

Thanks in advance,
Ricardo

Code ------>

// 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;

int main() {
  Tr tr;            // 3D-Delaunay triangulation
  C2t3 c2t3 (tr);   // 2D-complex in 3D-Delaunay triangulation

  // the 'function' is a 3D gray level image
  Gray_level_image image("Buddha_1024_1024_1024.inr", 1);

  // Carefully choosen bounding sphere: the center must be inside the
  // surface defined by 'image' and the radius must be high enough so that
  // the sphere actually bounds the whole image.
  GT::Point_3 bounding_sphere_center(512., 1024., 512.);
  GT::FT bounding_sphere_squared_radius = 512*512+1024*1024+512*512+1.;
  GT::Sphere_3 bounding_sphere(bounding_sphere_center,
                               bounding_sphere_squared_radius);

  // definition of the surface, with 10^-5 as relative precision
  Surface_3 surface(image, bounding_sphere, 1e-5);

  // defining meshing criteria
  CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30.,
                                                     5.,
                                                     5.);

  // meshing surface, with the "manifold without boundary" algorithm
  CGAL::make_surface_mesh(c2t3, surface, criteria, CGAL::Manifold_tag());

  std::ofstream out("CGALBuddha.off");
  CGAL::output_surface_facets_to_off (out, c2t3);
  std::cout << "Final number of points: " << tr.number_of_vertices() << 
"\n";
}
------>