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// Boost.Geometry (aka GGL, Generic Geometry Library)
// Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
// 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_GEOMETRY_POLICIES_RELATE_INTERSECTION_POINTS_HPP
#define BOOST_GEOMETRY_GEOMETRY_POLICIES_RELATE_INTERSECTION_POINTS_HPP
#include <algorithm>
#include <string>
#include <boost/concept_check.hpp>
#include <boost/numeric/conversion/cast.hpp>
#include <boost/geometry/algorithms/detail/assign_indexed_point.hpp>
#include <boost/geometry/core/access.hpp>
#include <boost/geometry/strategies/side_info.hpp>
#include <boost/geometry/util/promote_integral.hpp>
#include <boost/geometry/util/select_calculation_type.hpp>
#include <boost/geometry/util/select_most_precise.hpp>
#include <boost/geometry/util/math.hpp>
namespace boost { namespace geometry
{
namespace policies { namespace relate
{
/*!
\brief Policy calculating the intersection points themselves
*/
template
<
typename ReturnType
>
struct segments_intersection_points
{
typedef ReturnType return_type;
template
<
typename Point,
typename Segment,
typename SegmentRatio,
typename T
>
static inline void assign(Point& point,
Segment const& segment,
SegmentRatio const& ratio,
T const& dx, T const& dy)
{
typedef typename geometry::coordinate_type<Point>::type coordinate_type;
// Calculate the intersection point based on segment_ratio
// Up to now, division was postponed. Here we divide using numerator/
// denominator. In case of integer this results in an integer
// division.
BOOST_ASSERT(ratio.denominator() != 0);
typedef typename promote_integral<coordinate_type>::type promoted_type;
promoted_type const numerator
= boost::numeric_cast<promoted_type>(ratio.numerator());
promoted_type const denominator
= boost::numeric_cast<promoted_type>(ratio.denominator());
promoted_type const dx_promoted = boost::numeric_cast<promoted_type>(dx);
promoted_type const dy_promoted = boost::numeric_cast<promoted_type>(dy);
set<0>(point, get<0, 0>(segment) + boost::numeric_cast
<
coordinate_type
>(numerator * dx_promoted / denominator));
set<1>(point, get<0, 1>(segment) + boost::numeric_cast
<
coordinate_type
>(numerator * dy_promoted / denominator));
}
template
<
typename Segment1,
typename Segment2,
typename SegmentIntersectionInfo
>
static inline return_type segments_crosses(side_info const&,
SegmentIntersectionInfo const& sinfo,
Segment1 const& s1, Segment2 const& s2)
{
return_type result;
result.count = 1;
if (sinfo.robust_ra < sinfo.robust_rb)
{
assign(result.intersections[0], s1, sinfo.robust_ra,
sinfo.dx_a, sinfo.dy_a);
}
else
{
assign(result.intersections[0], s2, sinfo.robust_rb,
sinfo.dx_b, sinfo.dy_b);
}
result.fractions[0].assign(sinfo);
return result;
}
template <typename Segment1, typename Segment2, typename Ratio>
static inline return_type segments_collinear(
Segment1 const& a, Segment2 const& b, bool /*opposite*/,
int a1_wrt_b, int a2_wrt_b, int b1_wrt_a, int b2_wrt_a,
Ratio const& ra_from_wrt_b, Ratio const& ra_to_wrt_b,
Ratio const& rb_from_wrt_a, Ratio const& rb_to_wrt_a)
{
return_type result;
unsigned int index = 0, count_a = 0, count_b = 0;
Ratio on_a[2];
// The conditions "index < 2" are necessary for non-robust handling,
// if index would be 2 this indicate an (currently uncatched) error
// IMPORTANT: the order of conditions is different as in direction.hpp
if (a1_wrt_b >= 1 && a1_wrt_b <= 3 // ra_from_wrt_b.on_segment()
&& index < 2)
{
// a1--------->a2
// b1----->b2
//
// ra1 (relative to b) is between 0/1:
// -> First point of A is intersection point
detail::assign_point_from_index<0>(a, result.intersections[index]);
result.fractions[index].assign(Ratio::zero(), ra_from_wrt_b);
on_a[index] = Ratio::zero();
index++;
count_a++;
}
if (b1_wrt_a == 2 //rb_from_wrt_a.in_segment()
&& index < 2)
{
// We take the first intersection point of B
// a1--------->a2
// b1----->b2
// But only if it is not located on A
// a1--------->a2
// b1----->b2 rb_from_wrt_a == 0/1 -> a already taken
detail::assign_point_from_index<0>(b, result.intersections[index]);
result.fractions[index].assign(rb_from_wrt_a, Ratio::zero());
on_a[index] = rb_from_wrt_a;
index++;
count_b++;
}
if (a2_wrt_b >= 1 && a2_wrt_b <= 3 //ra_to_wrt_b.on_segment()
&& index < 2)
{
// Similarly, second IP (here a2)
// a1--------->a2
// b1----->b2
detail::assign_point_from_index<1>(a, result.intersections[index]);
result.fractions[index].assign(Ratio::one(), ra_to_wrt_b);
on_a[index] = Ratio::one();
index++;
count_a++;
}
if (b2_wrt_a == 2 // rb_to_wrt_a.in_segment()
&& index < 2)
{
detail::assign_point_from_index<1>(b, result.intersections[index]);
result.fractions[index].assign(rb_to_wrt_a, Ratio::one());
on_a[index] = rb_to_wrt_a;
index++;
count_b++;
}
// TEMPORARY
// If both are from b, and b is reversed w.r.t. a, we swap IP's
// to align them w.r.t. a
// get_turn_info still relies on some order (in some collinear cases)
if (index == 2 && on_a[1] < on_a[0])
{
std::swap(result.fractions[0], result.fractions[1]);
std::swap(result.intersections[0], result.intersections[1]);
}
result.count = index;
return result;
}
static inline return_type disjoint()
{
return return_type();
}
static inline return_type error(std::string const&)
{
return return_type();
}
// Both degenerate
template <typename Segment>
static inline return_type degenerate(Segment const& segment, bool)
{
return_type result;
result.count = 1;
set<0>(result.intersections[0], get<0, 0>(segment));
set<1>(result.intersections[0], get<0, 1>(segment));
return result;
}
// One degenerate
template <typename Segment, typename Ratio>
static inline return_type one_degenerate(Segment const& degenerate_segment,
Ratio const& ratio, bool a_degenerate)
{
return_type result;
result.count = 1;
set<0>(result.intersections[0], get<0, 0>(degenerate_segment));
set<1>(result.intersections[0], get<0, 1>(degenerate_segment));
if (a_degenerate)
{
// IP lies on ratio w.r.t. segment b
result.fractions[0].assign(Ratio::zero(), ratio);
}
else
{
result.fractions[0].assign(ratio, Ratio::zero());
}
return result;
}
};
}} // namespace policies::relate
}} // namespace boost::geometry
#endif // BOOST_GEOMETRY_GEOMETRY_POLICIES_RELATE_INTERSECTION_POINTS_HPP
|
