From e4e7bd4a286997d244ac9a777dc916dcb60ebc4a Mon Sep 17 00:00:00 2001
From: Adam Wulkiewicz <adam.wulkiewicz@gmail.com>
Date: Fri, 3 May 2013 20:36:29 +0000
Subject: [PATCH] geometry.index: added segment_intersection algorithm.

[SVN r84129]
---
 .../algorithms/segment_intersection.hpp       | 141 ++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 include/boost/geometry/index/detail/algorithms/segment_intersection.hpp

diff --git a/include/boost/geometry/index/detail/algorithms/segment_intersection.hpp b/include/boost/geometry/index/detail/algorithms/segment_intersection.hpp
new file mode 100644
index 000000000..b4389a8ec
--- /dev/null
+++ b/include/boost/geometry/index/detail/algorithms/segment_intersection.hpp
@@ -0,0 +1,141 @@
+// Boost.Geometry Index
+//
+// n-dimensional box-segment intersection
+//
+// Copyright (c) 2011-2013 Adam Wulkiewicz, Lodz, Poland.
+//
+// Use, modification and distribution is subject to the Boost Software License,
+// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_SEGMENT_INTERSECTION_HPP
+#define BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_SEGMENT_INTERSECTION_HPP
+
+#include <boost/geometry/index/detail/indexable.hpp>
+
+namespace boost { namespace geometry { namespace index { namespace detail {
+
+template <typename Indexable, typename Point>
+struct default_relative_distance_type
+{
+    typedef typename select_most_precise<
+        typename select_most_precise<
+            typename traits::coordinate_type<Indexable>::type,
+            typename traits::coordinate_type<Point>::type
+        >::type,
+        float // TODO - use bigger type, calculated from the size of coordinate types
+    >::type type;
+
+
+    BOOST_MPL_ASSERT_MSG((!::boost::is_unsigned<type>::value),
+        THIS_TYPE_SHOULDNT_BE_UNSIGNED, (type));
+};
+
+namespace dispatch {
+
+template <typename Box, typename Point, size_t I>
+struct box_segment_intersection_dim
+{
+    BOOST_STATIC_ASSERT(I < traits::dimension<Box>::value);
+    BOOST_STATIC_ASSERT(I < traits::dimension<Point>::value);
+    BOOST_STATIC_ASSERT(traits::dimension<Point>::value == traits::dimension<Box>::value);
+
+    typedef typename default_relative_distance_type<Box, Point>::type relative_distance_type;
+
+    // WARNING! - relative_distance_type must be IEEE float for this to work
+
+    static inline bool apply(Box const& b, Point const& p0, Point const& p1,
+                             relative_distance_type & t_near, relative_distance_type & t_far)
+    {
+        relative_distance_type ray_d = geometry::get<I>(p1) - geometry::get<I>(p0);
+        relative_distance_type tn = ( detail::get<min_corner, I>(b) - geometry::get<I>(p0) ) / ray_d;
+        relative_distance_type tf = ( detail::get<max_corner, I>(b) - geometry::get<I>(p0) ) / ray_d;
+        if ( tf < tn )
+            ::std::swap(tn, tf);
+
+        if ( t_near < tn )
+            t_near = tn;
+        if ( tf < t_far )
+            t_far = tf;
+
+        return 0 <= t_far && t_near <= t_far;
+    }
+};
+
+template <typename Box, typename Point, size_t CurrentDimension>
+struct box_segment_intersection
+{
+    BOOST_STATIC_ASSERT(0 < CurrentDimension);
+
+    typedef box_segment_intersection_dim<Box, Point, CurrentDimension - 1> for_dim;
+    typedef typename for_dim::relative_distance_type relative_distance_type;
+
+    static inline bool apply(Box const& b, Point const& p0, Point const& p1,
+                             relative_distance_type & t_near, relative_distance_type & t_far)
+    {
+        return box_segment_intersection<Box, Point, CurrentDimension - 1>::apply(b, p0, p1, t_near, t_far)
+            && for_dim::apply(b, p0, p1, t_near, t_far);
+    }
+};
+
+template <typename Box, typename Point>
+struct box_segment_intersection<Box, Point, 1>
+{
+    typedef box_segment_intersection_dim<Box, Point, 0> for_dim;
+    typedef typename for_dim::relative_distance_type relative_distance_type;
+
+    static inline bool apply(Box const& b, Point const& p0, Point const& p1,
+                             relative_distance_type & t_near, relative_distance_type & t_far)
+    {
+        return for_dim::apply(b, p0, p1, t_near, t_far);
+    }
+};
+
+template <typename Indexable, typename Point, typename Tag>
+struct segment_intersection
+{
+    BOOST_MPL_ASSERT_MSG((false), NOT_IMPLEMENTED_FOR_THIS_GEOMETRY, (segment_intersection));
+};
+
+template <typename Indexable, typename Point>
+struct segment_intersection<Indexable, Point, point_tag>
+{
+    BOOST_MPL_ASSERT_MSG((false), SEGMENT_POINT_INTERSECTION_UNAVAILABLE, (segment_intersection));
+};
+
+template <typename Indexable, typename Point>
+struct segment_intersection<Indexable, Point, box_tag>
+{
+    typedef dispatch::box_segment_intersection<Indexable, Point, detail::traits::dimension<Indexable>::value> impl;
+    typedef typename impl::relative_distance_type relative_distance_type;
+
+    static inline bool apply(Indexable const& b, Point const& p0, Point const& p1, relative_distance_type & relative_distance)
+    {
+        relative_distance_type t_near = -(::std::numeric_limits<relative_distance_type>::max)();
+        relative_distance_type t_far = (::std::numeric_limits<relative_distance_type>::max)();
+
+        return impl::apply(b, p0, p1, t_near, t_far) &&
+               (t_near <= 1) &&
+               ( relative_distance = 0 < t_near ? t_near : 0, true );
+    }
+};
+
+} // namespace dispatch
+
+template <typename Indexable, typename Point> inline
+bool segment_intersection(Indexable const& b,
+                          Point const& p0,
+                          Point const& p1,
+                          typename default_relative_distance_type<Indexable, Point>::type & relative_distance)
+{
+    // TODO check Indexable and Point concepts
+
+    return dispatch::segment_intersection<
+            Indexable, Point,
+            typename detail::traits::tag<Indexable>::type
+        >::apply(b, p0, p1, relative_distance);
+}
+
+}}}} // namespace boost::geometry::index::detail
+
+#endif // BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_SEGMENT_INTERSECTION_HPP