detail/distance/segment_to_segment.hpp

0001 // Boost.Geometry (aka GGL, Generic Geometry Library)
0002
0003 // Copyright (c) 2023 Adam Wulkiewicz, Lodz, Poland.
0004
0005 // Copyright (c) 2014-2021, Oracle and/or its affiliates.
0006 // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
0007 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
0008
0009 // Licensed under the Boost Software License version 1.0.
0010 // http://www.boost.org/users/license.html
0011
0012 #ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_DISTANCE_SEGMENT_TO_SEGMENT_HPP
0013 #define BOOST_GEOMETRY_ALGORITHMS_DETAIL_DISTANCE_SEGMENT_TO_SEGMENT_HPP
0014
0015 #include <algorithm>
0016 #include <iterator>
0017
0018 #include <boost/core/addressof.hpp>
0019
0020 #include <boost/geometry/algorithms/assign.hpp>
0021 #include <boost/geometry/algorithms/detail/distance/is_comparable.hpp>
0022 #include <boost/geometry/algorithms/detail/distance/strategy_utils.hpp>
0023 #include <boost/geometry/algorithms/dispatch/distance.hpp>
0024 #include <boost/geometry/algorithms/intersects.hpp>
0025
0026 #include <boost/geometry/core/point_type.hpp>
0027 #include <boost/geometry/core/tags.hpp>
0028
0029 #include <boost/geometry/strategies/distance.hpp>
0030 #include <boost/geometry/strategies/tags.hpp>
0031
0032 #include <boost/geometry/util/constexpr.hpp>
0033
0034
0035 namespace boost { namespace geometry
0036 {
0037
0038
0039 #ifndef DOXYGEN_NO_DETAIL
0040 namespace detail { namespace distance
0041 {
0042
0043
0044
0045 // compute segment-segment distance
0046 template<typename Segment1, typename Segment2, typename Strategies>
0047 class segment_to_segment
0048 {
0049     typedef distance::strategy_t<Segment1, Segment2, Strategies> strategy_type;
0050
0051 public:
0052     typedef distance::return_t<Segment1, Segment2, Strategies> return_type;
0053
0054     static inline return_type apply(Segment1 const& segment1, Segment2 const& segment2,
0055                                     Strategies const& strategies)
0056     {
0057         if (geometry::intersects(segment1, segment2, strategies))
0058         {
0059             return 0;
0060         }
0061
0062         typename point_type<Segment1>::type p[2];
0063         detail::assign_point_from_index<0>(segment1, p[0]);
0064         detail::assign_point_from_index<1>(segment1, p[1]);
0065
0066         typename point_type<Segment2>::type q[2];
0067         detail::assign_point_from_index<0>(segment2, q[0]);
0068         detail::assign_point_from_index<1>(segment2, q[1]);
0069
0070         strategy_type const strategy = strategies.distance(segment1, segment2);
0071
0072         auto const cstrategy = strategy::distance::services::get_comparable
0073                                 <
0074                                     strategy_type
0075                                 >::apply(strategy);
0076
0077         distance::creturn_t<Segment1, Segment2, Strategies> d[4];
0078         d[0] = cstrategy.apply(q[0], p[0], p[1]);
0079         d[1] = cstrategy.apply(q[1], p[0], p[1]);
0080         d[2] = cstrategy.apply(p[0], q[0], q[1]);
0081         d[3] = cstrategy.apply(p[1], q[0], q[1]);
0082
0083         std::size_t imin = std::distance(boost::addressof(d[0]),
0084                                          std::min_element(d, d + 4));
0085
0086         if BOOST_GEOMETRY_CONSTEXPR (is_comparable<strategy_type>::value)
0087         {
0088             return d[imin];
0089         }
0090         else // else prevents unreachable code warning
0091         {
0092             switch (imin)
0093             {
0094             case 0:
0095                 return strategy.apply(q[0], p[0], p[1]);
0096             case 1:
0097                 return strategy.apply(q[1], p[0], p[1]);
0098             case 2:
0099                 return strategy.apply(p[0], q[0], q[1]);
0100             default:
0101                 return strategy.apply(p[1], q[0], q[1]);
0102             }
0103         }
0104     }
0105 };
0106
0107
0108
0109
0110 }} // namespace detail::distance
0111 #endif // DOXYGEN_NO_DETAIL
0112
0113
0114 #ifndef DOXYGEN_NO_DISPATCH
0115 namespace dispatch
0116 {
0117
0118
0119
0120 // segment-segment
0121 template <typename Segment1, typename Segment2, typename Strategy>
0122 struct distance
0123     <
0124         Segment1, Segment2, Strategy, segment_tag, segment_tag,
0125         strategy_tag_distance_point_segment, false
0126     >
0127     : detail::distance::segment_to_segment<Segment1, Segment2, Strategy>
0128 {};
0129
0130
0131
0132 } // namespace dispatch
0133 #endif // DOXYGEN_NO_DISPATCH
0134
0135
0136 }} // namespace boost::geometry
0137
0138
0139 #endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_DISTANCE_SEGMENT_TO_SEGMENT_HPP