policies/relate/intersection_ratios.hpp

0001 // Boost.Geometry (aka GGL, Generic Geometry Library)
0002
0003 // Copyright (c) 2007-2014 Barend Gehrels, Amsterdam, the Netherlands.
0004
0005 // Use, modification and distribution is subject to the Boost Software License,
0006 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0007 // http://www.boost.org/LICENSE_1_0.txt)
0008
0009 #ifndef BOOST_GEOMETRY_GEOMETRY_POLICIES_RELATE_INTERSECTION_RATIOS_HPP
0010 #define BOOST_GEOMETRY_GEOMETRY_POLICIES_RELATE_INTERSECTION_RATIOS_HPP
0011
0012
0013 #include <algorithm>
0014 #include <string>
0015
0016 #include <boost/concept_check.hpp>
0017
0018 #include <boost/geometry/algorithms/detail/assign_indexed_point.hpp>
0019 #include <boost/geometry/core/access.hpp>
0020 #include <boost/geometry/strategies/side_info.hpp>
0021
0022
0023 namespace boost { namespace geometry
0024 {
0025
0026 namespace policies { namespace relate
0027 {
0028
0029
0030 /*!
0031 \brief Policy returning segment ratios
0032 \note Template argument FractionType should be a fraction_type<SegmentRatio>
0033  */
0034 template
0035 <
0036     typename FractionType
0037 >
0038 struct segments_intersection_ratios
0039 {
0040     typedef FractionType return_type;
0041
0042     template
0043     <
0044         typename Segment1,
0045         typename Segment2,
0046         typename SegmentIntersectionInfo
0047     >
0048     static inline return_type segments_crosses(side_info const&,
0049                     SegmentIntersectionInfo const& sinfo,
0050                     Segment1 const& , Segment2 const& )
0051     {
0052         return_type result;
0053         result.assign(sinfo);
0054         return result;
0055     }
0056
0057     template<typename SegmentIntersectionInfo, typename Point>
0058     static inline return_type
0059     segments_share_common_point(side_info const&, SegmentIntersectionInfo const& sinfo,
0060                                 Point const& p)
0061     {
0062         return_type result;
0063         result.assign(sinfo);
0064         return result;
0065     }
0066
0067     template <typename Segment1, typename Segment2, typename Ratio>
0068     static inline return_type segments_collinear(
0069         Segment1 const& , Segment2 const& ,
0070         Ratio const& ra_from_wrt_b, Ratio const& ra_to_wrt_b,
0071         Ratio const& rb_from_wrt_a, Ratio const& rb_to_wrt_a)
0072     {
0073         // We have only one result, for (potentially) two IP's,
0074         // so we take a first one
0075         return_type result;
0076
0077         if (ra_from_wrt_b.on_segment())
0078         {
0079             result.assign(Ratio::zero(), ra_from_wrt_b);
0080         }
0081         else if (rb_from_wrt_a.in_segment())
0082         {
0083             result.assign(rb_from_wrt_a, Ratio::zero());
0084         }
0085         else if (ra_to_wrt_b.on_segment())
0086         {
0087             result.assign(Ratio::one(), ra_to_wrt_b);
0088         }
0089         else if (rb_to_wrt_a.in_segment())
0090         {
0091             result.assign(rb_to_wrt_a, Ratio::one());
0092         }
0093
0094         return result;
0095     }
0096
0097     static inline return_type disjoint()
0098     {
0099         return return_type();
0100     }
0101     static inline return_type error(std::string const&)
0102     {
0103         return return_type();
0104     }
0105
0106     template <typename Segment>
0107     static inline return_type degenerate(Segment const& segment, bool)
0108     {
0109         return return_type();
0110     }
0111
0112     template <typename Segment, typename Ratio>
0113     static inline return_type one_degenerate(Segment const& ,
0114             Ratio const& ratio, bool a_degenerate)
0115     {
0116         return_type result;
0117         if (a_degenerate)
0118         {
0119             // IP lies on ratio w.r.t. segment b
0120             result.assign(Ratio::zero(), ratio);
0121         }
0122         else
0123         {
0124             result.assign(ratio, Ratio::zero());
0125         }
0126         return result;
0127     }
0128
0129 };
0130
0131
0132 }} // namespace policies::relate
0133
0134 }} // namespace boost::geometry
0135
0136 #endif // BOOST_GEOMETRY_GEOMETRY_POLICIES_RELATE_INTERSECTION_RATIOS_HPP