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// Copyright (c) 2000
// Utrecht University (The Netherlands),
// ETH Zurich (Switzerland),
// INRIA Sophia-Antipolis (France),
// Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel). All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Intersections_2/include/CGAL/Intersections_2/Line_2_Triangle_2.h $
// $Id: include/CGAL/Intersections_2/Line_2_Triangle_2.h b26b07a1242 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s) : Geert-Jan Giezeman
#ifndef CGAL_INTERSECTIONS_2_LINE_2_TRIANGLE_2_H
#define CGAL_INTERSECTIONS_2_LINE_2_TRIANGLE_2_H
#include <CGAL/Line_2.h>
#include <CGAL/Segment_2.h>
#include <CGAL/Triangle_2.h>
#include <CGAL/Point_2.h>
#include <CGAL/Intersections_2/internal/Straight_2.h>
#include <CGAL/kernel_assertions.h>
#include <CGAL/number_utils.h>
#include <CGAL/Intersection_traits_2.h>
namespace CGAL {
namespace Intersections {
namespace internal {
template <class K>
class Line_2_Triangle_2_pair {
public:
enum Intersection_results {NO_INTERSECTION, POINT, SEGMENT, UNKNOWN};
Line_2_Triangle_2_pair(typename K::Line_2 const *line,
typename K::Triangle_2 const *trian)
: _line(line), _trian(trian) {}
Intersection_results intersection_type() const;
typename K::Point_2 intersection_point() const;
typename K::Segment_2 intersection_segment() const;
protected:
typename K::Line_2 const*_line;
typename K::Triangle_2 const * _trian;
mutable Intersection_results _result = UNKNOWN;
mutable typename K::Point_2 _intersection_point;
mutable typename K::Point_2 _other_point;
};
template <class K>
inline
typename K::Boolean
do_intersect(const typename K::Line_2& l,
const typename K::Triangle_2& tr,
const K&)
{
typedef Line_2_Triangle_2_pair<K> pair_t;
pair_t pair(&l, &tr);
return pair.intersection_type() != pair_t::NO_INTERSECTION;
}
template <class K>
inline
typename K::Boolean
do_intersect(const typename K::Triangle_2& tr,
const typename K::Line_2& l,
const K& k)
{
return internal::do_intersect(l, tr, k);
}
template <class K>
typename Line_2_Triangle_2_pair<K>::Intersection_results
Line_2_Triangle_2_pair<K>::intersection_type() const
{
typedef typename K::Line_2 Line_2;
if (_result!=UNKNOWN)
return _result;
// The non const this pointer is used to cast away const.
Straight_2_<K> straight(*_line);
Line_2 l(_trian->vertex(0), _trian->vertex(1));
if (l.oriented_side(_trian->vertex(2)) == ON_POSITIVE_SIDE) {
// if (_trian->is_counterclockwise()) {
straight.cut_right_off(
Line_2(_trian->vertex(0), _trian->vertex(1)));
straight.cut_right_off(
Line_2(_trian->vertex(1), _trian->vertex(2)));
straight.cut_right_off(
Line_2(_trian->vertex(2), _trian->vertex(0)));
} else {
straight.cut_right_off(
Line_2(_trian->vertex(2), _trian->vertex(1)));
straight.cut_right_off(
Line_2(_trian->vertex(1), _trian->vertex(0)));
straight.cut_right_off(
Line_2(_trian->vertex(0), _trian->vertex(2)));
}
switch (straight.current_state()) {
case Straight_2_<K>::EMPTY:
_result = NO_INTERSECTION;
return _result;
case Straight_2_<K>::POINT: {
straight.current(_intersection_point);
_result = POINT;
return _result;
}
case Straight_2_<K>::SEGMENT: {
typename K::Segment_2 seg;
straight.current(seg);
_intersection_point = seg.source();
_other_point = seg.target();
_result = SEGMENT;
return _result;
}
default: // should not happen.
CGAL_kernel_assertion_msg(false, "Internal CGAL error.");
_result = NO_INTERSECTION;
return _result;
}
}
template <class K>
typename K::Point_2
Line_2_Triangle_2_pair<K>::
intersection_point() const
{
if (_result==UNKNOWN)
intersection_type();
CGAL_kernel_assertion(_result == POINT);
return _intersection_point;
}
template <class K>
typename K::Segment_2
Line_2_Triangle_2_pair<K>::
intersection_segment() const
{
typedef typename K::Segment_2 Segment_2;
if (_result==UNKNOWN)
intersection_type();
CGAL_kernel_assertion(_result == SEGMENT);
return Segment_2(_intersection_point, _other_point);
}
template <class K>
typename CGAL::Intersection_traits
<K, typename K::Line_2, typename K::Triangle_2>::result_type
intersection(const typename K::Line_2 &line,
const typename K::Triangle_2 &tr,
const K&)
{
typedef Line_2_Triangle_2_pair<K> is_t;
is_t ispair(&line, &tr);
switch (ispair.intersection_type()) {
case is_t::NO_INTERSECTION:
default:
return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Triangle_2>();
case is_t::POINT:
return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Triangle_2>(ispair.intersection_point());
case is_t::SEGMENT:
return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Triangle_2>(ispair.intersection_segment());
}
}
template <class K>
inline
typename CGAL::Intersection_traits
<K, typename K::Line_2, typename K::Triangle_2>::result_type
intersection(const typename K::Triangle_2 &tr,
const typename K::Line_2 &line,
const K& k)
{
return internal::intersection(line, tr, k);
}
} // namespace internal
} // namespace Intersections
CGAL_INTERSECTION_FUNCTION(Line_2, Triangle_2, 2)
CGAL_DO_INTERSECT_FUNCTION(Line_2, Triangle_2, 2)
} // namespace CGAL
#endif // CGAL_INTERSECTIONS_2_LINE_2_TRIANGLE_2_H
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