 CGAL 5.6 - 3D Polyhedral Surface
CGAL::Polyhedron_traits_with_normals_3< Kernel > Class Template Reference

#include <CGAL/Polyhedron_traits_with_normals_3.h>

## Definition

The class Polyhedron_traits_with_normals_3 is a model of the PolyhedronTraits_3 concept.

It defines the geometric types and primitive operations used in the polyhedral surface data structure Polyhedron_3<PolyhedronTraits_3>. Polyhedron_traits_with_normals_3 uses the normal vector from Kernel for the plane equation in facets. It keeps a local copy of the kernel which makes it suitable for kernels with local state.

Is Model Of:
PolyhedronTraits_3
CGAL::Polyhedron_traits_3<Kernel>

Example

We use this traits class to instantiate a polyhedral surface with a normal vector and no plane equation for each facet. We compute the normal vector assuming exact arithmetic (integers in this example) and convex planar facets.

#include <CGAL/Homogeneous.h>
#include <CGAL/Polyhedron_traits_with_normals_3.h>
#include <CGAL/Polyhedron_3.h>
#include <iostream>
#include <algorithm>
struct Normal_vector {
template <class Facet>
typename Facet::Plane_3 operator()( Facet& f) {
typename Facet::Halfedge_handle h = f.halfedge();
// Facet::Plane_3 is the normal vector type. We assume the
// CGAL Kernel here and use its global functions.
h->next()->vertex()->point() - h->vertex()->point(),
h->next()->next()->vertex()->point() - h->next()->vertex()->point());
}
};
typedef Kernel::Vector_3 Vector_3;
typedef CGAL::Polyhedron_3<Traits> Polyhedron;
int main() {
Point_3 p( 1, 0, 0);
Point_3 q( 0, 1, 0);
Point_3 r( 0, 0, 1);
Point_3 s( 0, 0, 0);
Polyhedron P;
P.make_tetrahedron( p, q, r, s);
std::transform( P.facets_begin(), P.facets_end(), P.planes_begin(),
Normal_vector());
std::copy( P.planes_begin(), P.planes_end(),
std::ostream_iterator<Vector_3>( std::cout, "\n"));
return 0;
}
Examples:
Polyhedron/polyhedron_prog_normals.cpp.

## Types

typedef unspecified_type Kernel
the Kernel model.

typedef Kernel::Point_3 Point_3

typedef Kernel::Vector_3 Plane_3

typedef Kernel::Construct_opposite_vector_3 Construct_opposite_plane_3

## Creation

Polyhedron_traits_with_normals_3 ()
default constructor, uses Kernel() as local reference to the kernel.

Polyhedron_traits_with_normals_3 (const Kernel &kernel)
stores kernel as local reference.

## Operations

Construct_opposite_plane_3 construct_opposite_plane_3_object ()
forwarded to kernel.