Quando comecei com a CGAL, quase imediatamente encontrei esse problema. Consegui encontrar uma solução depois de ler atentamente a documentação da malha poligonal . Essencialmente, por meio de uma versão modificada do Corefinement , você pode mesclar suavemente duas geometrias separadas, independentemente da sua contagem ou forma de polis (no entanto, quanto maior a diferença de polígonos, menos eficaz ele se tornará).
O que você precisa fazer é primeiro, verifique se a geometria não se intercepta. Em segundo lugar, verifique se CGAL::Polygon_mesh_processing::clip()
está ativo nas duas geometrias (sugiro usar close_volumes=false
). Em seguida, calcule a união das duas novas malhas:
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/Polygon_mesh_processing/corefinement.h>
#include <fstream>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Surface_mesh<K::Point_3> Mesh;
namespace PMP = CGAL::Polygon_mesh_processing;
int main(int argc, char* argv[])
{
const char* filename1 = (argc > 1) ? argv[1] : "data/blobby.off";
const char* filename2 = (argc > 2) ? argv[2] : "data/eight.off";
std::ifstream input(filename1);
Mesh mesh1, mesh2;
if (!input || !(input >> mesh1))
{
std::cerr << "First mesh is not a valid off file." << std::endl;
return 1;
}
input.close();
input.open(filename2);
if (!input || !(input >> mesh2))
{
std::cerr << "Second mesh is not a valid off file." << std::endl;
return 1;
}
Mesh out;
bool valid_union = PMP::corefine_and_compute_union(mesh1,mesh2, out);
if (valid_union)
{
std::cout << "Union was successfully computed\n";
std::ofstream output("union.off");
output << out;
return 0;
}
std::cout << "Union could not be computed\n";
return 1;
}
Em vez de usar uma malha com um ponto de um kernel com construções exatas, os pontos exatos são uma propriedade dos vértices da malha que podemos reutilizar em operações posteriores. Com essa propriedade, podemos manipular uma malha com pontos com coordenadas de ponto flutuante, mas nos beneficiamos da robustez fornecida pelas construções exatas .:
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/Polygon_mesh_processing/corefinement.h>
#include <fstream>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Exact_predicates_exact_constructions_kernel EK;
typedef CGAL::Surface_mesh<K::Point_3> Mesh;
typedef boost::graph_traits<Mesh>::vertex_descriptor vertex_descriptor;
typedef Mesh::Property_map<vertex_descriptor,EK::Point_3> Exact_point_map;
typedef Mesh::Property_map<vertex_descriptor,bool> Exact_point_computed;
namespace PMP = CGAL::Polygon_mesh_processing;
namespace params = PMP::parameters;
struct Coref_point_map
{
// typedef for the property map
typedef boost::property_traits<Exact_point_map>::value_type value_type;
typedef boost::property_traits<Exact_point_map>::reference reference;
typedef boost::property_traits<Exact_point_map>::category category;
typedef boost::property_traits<Exact_point_map>::key_type key_type;
// exterior references
Exact_point_computed* exact_point_computed_ptr;
Exact_point_map* exact_point_ptr;
Mesh* mesh_ptr;
Exact_point_computed& exact_point_computed() const
{
CGAL_assertion(exact_point_computed_ptr!=NULL);
return *exact_point_computed_ptr;
}
Exact_point_map& exact_point() const
{
CGAL_assertion(exact_point_ptr!=NULL);
return *exact_point_ptr;
}
Mesh& mesh() const
{
CGAL_assertion(mesh_ptr!=NULL);
return *mesh_ptr;
}
// Converters
CGAL::Cartesian_converter<K, EK> to_exact;
CGAL::Cartesian_converter<EK, K> to_input;
Coref_point_map()
: exact_point_computed_ptr(NULL)
, exact_point_ptr(NULL)
, mesh_ptr(NULL)
{}
Coref_point_map(Exact_point_map& ep,
Exact_point_computed& epc,
Mesh& m)
: exact_point_computed_ptr(&epc)
, exact_point_ptr(&ep)
, mesh_ptr(&m)
{}
friend
reference get(const Coref_point_map& map, key_type k)
{
// create exact point if it does not exist
if (!map.exact_point_computed()[k]){
map.exact_point()[k]=map.to_exact(map.mesh().point(k));
map.exact_point_computed()[k]=true;
}
return map.exact_point()[k];
}
friend
void put(const Coref_point_map& map, key_type k, const EK::Point_3& p)
{
map.exact_point_computed()[k]=true;
map.exact_point()[k]=p;
// create the input point from the exact one
map.mesh().point(k)=map.to_input(p);
}
};
int main(int argc, char* argv[])
{
const char* filename1 = (argc > 1) ? argv[1] : "data/blobby.off";
const char* filename2 = (argc > 2) ? argv[2] : "data/eight.off";
std::ifstream input(filename1);
Mesh mesh1, mesh2;
if (!input || !(input >> mesh1))
{
std::cerr << "First mesh is not a valid off file." << std::endl;
return 1;
}
input.close();
input.open(filename2);
if (!input || !(input >> mesh2))
{
std::cerr << "Second mesh is not a valid off file." << std::endl;
return 1;
}
Exact_point_map mesh1_exact_points =
mesh1.add_property_map<vertex_descriptor,EK::Point_3>("e:exact_point").first;
Exact_point_computed mesh1_exact_points_computed =
mesh1.add_property_map<vertex_descriptor,bool>("e:exact_points_computed").first;
Exact_point_map mesh2_exact_points =
mesh2.add_property_map<vertex_descriptor,EK::Point_3>("e:exact_point").first;
Exact_point_computed mesh2_exact_points_computed =
mesh2.add_property_map<vertex_descriptor,bool>("e:exact_points_computed").first;
Coref_point_map mesh1_pm(mesh1_exact_points, mesh1_exact_points_computed, mesh1);
Coref_point_map mesh2_pm(mesh2_exact_points, mesh2_exact_points_computed, mesh2);
if ( PMP::corefine_and_compute_intersection(mesh1,
mesh2,
mesh1,
params::vertex_point_map(mesh1_pm),
params::vertex_point_map(mesh2_pm),
params::vertex_point_map(mesh1_pm) ) )
{
if ( PMP::corefine_and_compute_union(mesh1,
mesh2,
mesh2,
params::vertex_point_map(mesh1_pm),
params::vertex_point_map(mesh2_pm),
params::vertex_point_map(mesh2_pm) ) )
{
std::cout << "Intersection and union were successfully computed\n";
std::ofstream output("inter_union.off");
output << mesh2;
return 0;
}
std::cout << "Union could not be computed\n";
return 1;
}
std::cout << "Intersection could not be computed\n";
return 1;
}