Current File : //proc/self/root/usr/include/boost/geometry/strategies/cartesian/turn_in_ring_winding.hpp
// Boost.Geometry (aka GGL, Generic Geometry Library)
// Copyright (c) 2020 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_STRATEGIES_CARTESIAN_TURN_IN_RING_WINDING_HPP
#define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_TURN_IN_RING_WINDING_HPP
#include <boost/geometry/core/access.hpp>
#include <boost/geometry/core/config.hpp>
#include <boost/geometry/algorithms/detail/make/make.hpp>
namespace boost { namespace geometry
{
namespace strategy { namespace buffer
{
#ifndef DOXYGEN_NO_DETAIL
enum place_on_ring_type
{
// +----offsetted----> (offsetted is considered as outside)
// | |
// | |
// left right (first point outside, rest inside)
// | |
// | |
// <-----original----+ (original is considered as inside)
place_on_ring_offsetted,
place_on_ring_original,
place_on_ring_to_offsetted,
place_on_ring_from_offsetted,
};
template <typename CalculationType>
class turn_in_ring_winding
{
// Implements the winding rule.
// Basic calculations (on a clockwise ring of 5 segments)
// (as everywhere in BG, -1 = right, 0 = on segment, +1 = left)
// +--------2--------+ // P : For 1/3, nothing happens, it returns
// | | // For 2, side is right (-1), multiplier=2, -2
// | P | // For 4, side is right (-1), multiplier=1, -1
// 1 3 // For 5, side is right (-1), multiplier=1, -1, total -4
// | Q | // Q : For 2: -2, for 4: -2, total -4
// | | // R : For 2: -2, for 5: +2, total 0
// +----5---*----4---+ // S : For 2: -1, 3: nothing, 4: +1, total 0
//
// R S
//
public:
struct counter
{
inline counter()
: m_count(0)
, m_min_distance(0)
, m_close_to_offset(false)
{}
//! Returns -1 for outside, 1 for inside
inline int code() const
{
return m_count == 0 ? -1 : 1;
}
//! Counter, is increased if point is left of a segment (outside),
//! and decreased if point is right of a segment (inside)
int m_count;
//! Indicate an indication of distance. It is always set, unless
//! the point is located on the border-part of the original.
//! It is not guaranteed to be the minimum distance, because it is only
//! calculated for a selection of the offsetted ring.
CalculationType m_min_distance;
bool m_close_to_offset;
};
typedef counter state_type;
template <typename Point, typename PointOfSegment>
static inline bool in_vertical_range(Point const& point,
PointOfSegment const& s1,
PointOfSegment const& s2)
{
CalculationType const py = get<1>(point);
CalculationType const s1y = get<1>(s1);
CalculationType const s2y = get<1>(s2);
return (s1y >= py && s2y <= py)
|| (s2y >= py && s1y <= py);
}
template <typename Dm, typename Point, typename PointOfSegment>
static inline void apply_on_boundary(Point const& point,
PointOfSegment const& s1,
PointOfSegment const& s2,
place_on_ring_type place_on_ring,
counter& the_state)
{
if (place_on_ring == place_on_ring_offsetted)
{
// Consider the point as "outside"
the_state.m_count = 0;
the_state.m_close_to_offset = true;
the_state.m_min_distance = 0;
}
else if (place_on_ring == place_on_ring_to_offsetted
|| place_on_ring == place_on_ring_from_offsetted)
{
// Check distance from "point" to either s1 or s2
// on a line perpendicular to s1-s2
typedef model::infinite_line<CalculationType> line_type;
line_type const line
= detail::make::make_perpendicular_line<CalculationType>(s1, s2,
place_on_ring == place_on_ring_to_offsetted ? s2 : s1);
Dm perp;
perp.measure = arithmetic::side_value(line, point);
// If it is to the utmost point s1 or s2, it is "outside"
the_state.m_count = perp.is_zero() ? 0 : 1;
the_state.m_close_to_offset = true;
the_state.m_min_distance = std::fabs(perp.measure);
}
else
{
// It is on the border, the part of the original
// Consider it as "inside".
the_state.m_count = 1;
}
}
template <typename Dm, typename Point, typename PointOfSegment>
static inline bool apply(Point const& point,
PointOfSegment const& s1,
PointOfSegment const& s2,
Dm const& dm,
place_on_ring_type place_on_ring,
counter& the_state)
{
CalculationType const px = get<0>(point);
CalculationType const s1x = get<0>(s1);
CalculationType const s2x = get<0>(s2);
bool const in_horizontal_range
= (s1x >= px && s2x <= px)
|| (s2x >= px && s1x <= px);
bool const vertical = s1x == s2x;
bool const measured_on_boundary = dm.is_zero();
if (measured_on_boundary
&& (in_horizontal_range
|| (vertical && in_vertical_range(point, s1, s2))))
{
apply_on_boundary<Dm>(point, s1, s2, place_on_ring, the_state);
// Indicate that no further processing is necessary.
return false;
}
bool const is_on_right_side = dm.is_negative();
if (place_on_ring == place_on_ring_offsetted
&& is_on_right_side
&& (! the_state.m_close_to_offset
|| -dm.measure < the_state.m_min_distance))
{
// This part of the ring was the offsetted part,
// keep track of the distance WITHIN the ring
// with respect to the offsetted part
// NOTE: this is also done if it is NOT in the horizontal range.
the_state.m_min_distance = -dm.measure;
the_state.m_close_to_offset = true;
}
if (in_horizontal_range)
{
// Use only absolute comparisons, because the ring is continuous -
// what was missed is there earlier or later, and turns should
// not be counted twice (which can happen if an epsilon is used).
bool const eq1 = s1x == px;
bool const eq2 = s2x == px;
// Account for 1 or 2 for left side (outside)
// and for -1 or -2 for right side (inside)
int const side = is_on_right_side ? -1 : 1;
int const multiplier = eq1 || eq2 ? 1 : 2;
the_state.m_count += side * multiplier;
}
return true;
}
};
#endif // DOXYGEN_NO_DETAIL
}} // namespace strategy::buffer
}} // namespace boost::geometry
#endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_TURN_IN_RING_WINDING_HPP
Mini Shell