detail/distance/segment_to_segment.hpp

0001 // Boost.Geometry (aka GGL, Generic Geometry Library)
0002
0003 // Copyright (c) 2014-2021, Oracle and/or its affiliates.
0004
0005 // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
0006 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
0007
0008 // Licensed under the Boost Software License version 1.0.
0009 // http://www.boost.org/users/license.html
0010
0011 #ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_DISTANCE_SEGMENT_TO_SEGMENT_HPP
0012 #define BOOST_GEOMETRY_ALGORITHMS_DETAIL_DISTANCE_SEGMENT_TO_SEGMENT_HPP
0013
0014 #include <algorithm>
0015 #include <iterator>
0016
0017 #include <boost/core/addressof.hpp>
0018
0019 #include <boost/geometry/algorithms/assign.hpp>
0020 #include <boost/geometry/algorithms/detail/distance/is_comparable.hpp>
0021 #include <boost/geometry/algorithms/detail/distance/strategy_utils.hpp>
0022 #include <boost/geometry/algorithms/dispatch/distance.hpp>
0023 #include <boost/geometry/algorithms/intersects.hpp>
0024
0025 #include <boost/geometry/core/point_type.hpp>
0026 #include <boost/geometry/core/tags.hpp>
0027
0028 #include <boost/geometry/strategies/distance.hpp>
0029 #include <boost/geometry/strategies/tags.hpp>
0030
0031 #include <boost/geometry/util/condition.hpp>
0032
0033
0034 namespace boost { namespace geometry
0035 {
0036
0037
0038 #ifndef DOXYGEN_NO_DETAIL
0039 namespace detail { namespace distance
0040 {
0041
0042
0043
0044 // compute segment-segment distance
0045 template<typename Segment1, typename Segment2, typename Strategies>
0046 class segment_to_segment
0047 {
0048     typedef distance::strategy_t<Segment1, Segment2, Strategies> strategy_type;
0049
0050 public:
0051     typedef distance::return_t<Segment1, Segment2, Strategies> return_type;
0052
0053     static inline return_type apply(Segment1 const& segment1, Segment2 const& segment2,
0054                                     Strategies const& strategies)
0055     {
0056         if (geometry::intersects(segment1, segment2, strategies))
0057         {
0058             return 0;
0059         }
0060
0061         typename point_type<Segment1>::type p[2];
0062         detail::assign_point_from_index<0>(segment1, p[0]);
0063         detail::assign_point_from_index<1>(segment1, p[1]);
0064
0065         typename point_type<Segment2>::type q[2];
0066         detail::assign_point_from_index<0>(segment2, q[0]);
0067         detail::assign_point_from_index<1>(segment2, q[1]);
0068
0069         strategy_type const strategy = strategies.distance(segment1, segment2);
0070
0071         auto const cstrategy = strategy::distance::services::get_comparable
0072                                 <
0073                                     strategy_type
0074                                 >::apply(strategy);
0075
0076         distance::creturn_t<Segment1, Segment2, Strategies> d[4];
0077         d[0] = cstrategy.apply(q[0], p[0], p[1]);
0078         d[1] = cstrategy.apply(q[1], p[0], p[1]);
0079         d[2] = cstrategy.apply(p[0], q[0], q[1]);
0080         d[3] = cstrategy.apply(p[1], q[0], q[1]);
0081
0082         std::size_t imin = std::distance(boost::addressof(d[0]),
0083                                          std::min_element(d, d + 4));
0084
0085         if (BOOST_GEOMETRY_CONDITION(is_comparable<strategy_type>::value))
0086         {
0087             return d[imin];
0088         }
0089
0090         switch (imin)
0091         {
0092         case 0:
0093             return strategy.apply(q[0], p[0], p[1]);
0094         case 1:
0095             return strategy.apply(q[1], p[0], p[1]);
0096         case 2:
0097             return strategy.apply(p[0], q[0], q[1]);
0098         default:
0099             return strategy.apply(p[1], q[0], q[1]);
0100         }
0101     }
0102 };
0103
0104
0105
0106
0107 }} // namespace detail::distance
0108 #endif // DOXYGEN_NO_DETAIL
0109
0110
0111 #ifndef DOXYGEN_NO_DISPATCH
0112 namespace dispatch
0113 {
0114
0115
0116
0117 // segment-segment
0118 template <typename Segment1, typename Segment2, typename Strategy>
0119 struct distance
0120     <
0121         Segment1, Segment2, Strategy, segment_tag, segment_tag,
0122         strategy_tag_distance_point_segment, false
0123     >
0124     : detail::distance::segment_to_segment<Segment1, Segment2, Strategy>
0125 {};
0126
0127
0128
0129 } // namespace dispatch
0130 #endif // DOXYGEN_NO_DISPATCH
0131
0132
0133 }} // namespace boost::geometry
0134
0135
0136 #endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_DISTANCE_SEGMENT_TO_SEGMENT_HPP