Mesh_3/mesh_implicit_sphere_variable_size.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
 
#include <CGAL/Mesh_triangulation_3.h>
#include <CGAL/Mesh_complex_3_in_triangulation_3.h>
#include <CGAL/Mesh_criteria_3.h>
 
#include <CGAL/Labeled_mesh_domain_3.h>
#include <CGAL/make_mesh_3.h>
 
// Domain
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef K::FT FT;
typedef K::Point_3 Point;
typedef FT (Function)(const Point&);
typedef CGAL::Labeled_mesh_domain_3<K> Mesh_domain;
 
#ifdef CGAL_CONCURRENT_MESH_3
typedef CGAL::Parallel_tag Concurrency_tag;
#else
typedef CGAL::Sequential_tag Concurrency_tag;
#endif
 
// Triangulation
typedef CGAL::Mesh_triangulation_3<Mesh_domain,CGAL::Default,Concurrency_tag>::type Tr;
 
typedef CGAL::Mesh_complex_3_in_triangulation_3<Tr> C3t3;
 
// Criteria
typedef CGAL::Mesh_criteria_3<Tr> Mesh_criteria;
 
// Sizing field
struct Spherical_sizing_field
{
  typedef ::FT FT;
  typedef Point Point_3;
  typedef Mesh_domain::Index Index;
 
  FT operator()(const Point_3& p, const int, const Index&) const
  {
    FT sq_d_to_origin = CGAL::squared_distance(p, Point(CGAL::ORIGIN));
    return CGAL::abs( CGAL::sqrt(sq_d_to_origin)-0.5 ) / 5. + 0.025;
  }
};
 
namespace params = CGAL::parameters;
 
// Function
FT sphere_function (const Point& p)
{ return CGAL::squared_distance(p, Point(CGAL::ORIGIN))-1; }
 
int main()
{
  Mesh_domain domain = Mesh_domain::create_implicit_mesh_domain
    (sphere_function, K::Sphere_3(CGAL::ORIGIN, K::FT(2))
     );
 
  // Mesh criteria
  Spherical_sizing_field size;
  Mesh_criteria criteria(params::facet_angle(30).facet_size(0.1).facet_distance(0.025).
                                 cell_radius_edge_ratio(2).cell_size(size));
 
  // Mesh generation
  C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria, params::no_exude().no_perturb());
 
  // Output
  std::ofstream medit_file("out.mesh");
  CGAL::IO::write_MEDIT(medit_file, c3t3);
  medit_file.close();
 
  return 0;
}