CGAL 5.1.3 - CGAL and the Boost Graph Library
BGL_polyhedron_3/normals.cpp
#include <fstream>
#include <boost/graph/graph_traits.hpp>
#include <CGAL/Simple_cartesian.h>
#include <CGAL/Polyhedron_3.h>
#include <CGAL/Polyhedron_items_with_id_3.h>
#include <CGAL/property_map.h>
typedef Kernel::Point_3 Point;
typedef Kernel::Vector_3 Vector;
template<typename HalfedgeGraph,
typename PointMap,
typename NormalMap>
void calculate_face_normals(const HalfedgeGraph& g,
PointMap pm,
NormalMap nm)
{
typedef boost::graph_traits<HalfedgeGraph> GraphTraits;
typedef typename GraphTraits::face_iterator face_iterator;
typedef typename GraphTraits::halfedge_descriptor halfedge_descriptor;
typedef typename boost::property_traits<PointMap>::value_type point;
typedef typename boost::property_traits<NormalMap>::value_type normal;
face_iterator fb, fe;
for(boost::tie(fb, fe) = faces(g); fb != fe; ++fb)
{
halfedge_descriptor edg = halfedge(*fb, g);
halfedge_descriptor edgb = edg;
point p0 = pm[target(edg, g)];
edg = next(edg, g);
point p1 = pm[target(edg, g)];
edg = next(edg, g);
point p2 = pm[target(edg, g)];
edg = next(edg, g);
if(edg == edgb) {
// triangle
nm[*fb] = CGAL::unit_normal(p1, p2, p0);
} else {
// not a triangle
normal n(CGAL::NULL_VECTOR);
do {
n = n + CGAL::normal(p1, p2, p0);
p0 = p1;
p1 = p2;
edg = next(edg, g);
p2 = pm[target(edg, g)];
} while(edg != edgb);
nm[*fb] = n / CGAL::sqrt(n.squared_length());
}
}
}
int main(int argc, char** argv)
{
typedef boost::property_map<
Polyhedron,
>::const_type Face_index_map;
std::ifstream in((argc>1)?argv[1]:"cube.off");
Polyhedron P;
in >> P ;
// initialize facet indices
std::size_t i = 0;
for(Polyhedron::Facet_iterator it = P.facets_begin(); it != P.facets_end(); ++it, ++i)
{
it->id() = i;
}
// Ad hoc property_map to store normals. Face_index_map is used to
// map face_descriptors to a contiguous range of indices. See
// http://www.boost.org/libs/property_map/doc/vector_property_map.html
// for details.
boost::vector_property_map<Vector, Face_index_map>
normals(get(CGAL::face_index, P));
calculate_face_normals(
P // Graph
, get(CGAL::vertex_point, P) // map from vertex_descriptor to point
, normals // map from face_descriptor to Vector_3
);
std::cout << "Normals" << std::endl;
for(Polyhedron::Facet_iterator it = P.facets_begin(); it != P.facets_end(); ++it) {
// Facet_iterator is a face_descriptor, so we can use it as the
// key here
std::cout << normals[it] << std::endl;
}
return 0;
}