mirror of https://github.com/CGAL/cgal
88 lines
2.7 KiB
C++
88 lines
2.7 KiB
C++
// Copyright (c) 2013 GeometryFactory (France).
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// All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org).
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// You can redistribute it and/or modify it under the terms of the GNU
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// General Public License as published by the Free Software Foundation,
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// either version 3 of the License, or (at your option) any later version.
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//
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// Licensees holding a valid commercial license may use this file in
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// accordance with the commercial license agreement provided with the software.
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//
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// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
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// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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//
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// $URL$
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// $Id$
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//
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//
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// Author(s) : Ilker O. Yaz
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#ifndef CGAL_ORIENT_POLYHEDRON_3
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#define CGAL_ORIENT_POLYHEDRON_3
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#include <algorithm>
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#include <CGAL/internal/Operations_on_polyhedra/compute_normal.h>
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namespace CGAL{
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namespace internal{
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template <class Less_xyz>
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struct Compare_vertex_points_xyz_3{
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Less_xyz less;
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typedef bool result_type;
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template <class Vertex>
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bool operator()(const Vertex& v1, const Vertex& v2) const
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{
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return less(v1.point(), v2.point());
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}
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};
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} // end of namespace internal
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/**
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* Tests whether a closed polyhedron has a positive orientation.
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* A polyhedron is considered to have positive orientation if the normal vectors
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* of the facets point outside of the polyhedron. For each facet, its normal vector
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* is considered to point on the side of the facet where the sequence of vertices of
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* the facet is seen counterclockwise.
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* @pre @a `polyhedron`.is_closed()
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* @pre @a `polyhedron` is consistently oriented
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*
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* @tparam Polyhedron a %CGAL polyhedron
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*
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* @param polyhedron a closed polyhedron to be tested
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*
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* \todo The following only handle polyhedron with one connected component
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* the code, the sample example and the plugin must be updated.
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* @code
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* // use inside out to fix orientation
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* if(!is_oriented(polyhedron)) {
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* polyhedron.inside_out();
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* }
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* @endcode
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*/
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template<class Polyhedron>
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bool is_oriented(const Polyhedron& polyhedron)
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{
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typedef typename Polyhedron::Traits K;
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internal::Compare_vertex_points_xyz_3< typename K::Less_xyz_3 > less_xyz;
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typename Polyhedron::Vertex_const_iterator v_min
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= std::min_element(polyhedron.vertices_begin(), polyhedron.vertices_end(), less_xyz);
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const typename K::Vector_3& normal_v_min = compute_vertex_normal<typename Polyhedron::Vertex, K>(*v_min);
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return normal_v_min[0] < 0 || (
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normal_v_min[0] == 0 && (
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normal_v_min[1] < 0 ||
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( normal_v_min[1]==0 && normal_v_min[2] < 0 )
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)
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);
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}
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} // namespace CGAL
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#endif // CGAL_ORIENT_POLYHEDRON_3
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