161 lines
4.3 KiB
C++
161 lines
4.3 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
|
|
|
|
// Copyright (c) 2015 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_ALGORITHMS_IS_CONVEX_HPP
|
|
#define BOOST_GEOMETRY_ALGORITHMS_IS_CONVEX_HPP
|
|
|
|
|
|
#include <boost/geometry/core/access.hpp>
|
|
#include <boost/geometry/core/closure.hpp>
|
|
#include <boost/geometry/core/cs.hpp>
|
|
#include <boost/geometry/core/coordinate_dimension.hpp>
|
|
#include <boost/geometry/core/point_type.hpp>
|
|
#include <boost/geometry/algorithms/detail/equals/point_point.hpp>
|
|
#include <boost/geometry/iterators/ever_circling_iterator.hpp>
|
|
#include <boost/geometry/strategies/side.hpp>
|
|
#include <boost/geometry/strategies/cartesian/side_by_triangle.hpp>
|
|
#include <boost/geometry/views/detail/normalized_view.hpp>
|
|
|
|
namespace boost { namespace geometry
|
|
{
|
|
|
|
|
|
#ifndef DOXYGEN_NO_DETAIL
|
|
namespace detail { namespace is_convex
|
|
{
|
|
|
|
struct ring_is_convex
|
|
{
|
|
template <typename Ring>
|
|
static inline bool apply(Ring const& ring)
|
|
{
|
|
typedef typename geometry::point_type<Ring>::type point_type;
|
|
typedef typename strategy::side::services::default_strategy
|
|
<
|
|
typename cs_tag<point_type>::type
|
|
>::type side_strategy_type;
|
|
|
|
std::size_t n = boost::size(ring);
|
|
if (boost::size(ring) < core_detail::closure::minimum_ring_size
|
|
<
|
|
geometry::closure<Ring>::value
|
|
>::value)
|
|
{
|
|
// (Too) small rings are considered as non-concave, is convex
|
|
return true;
|
|
}
|
|
|
|
// Walk in clockwise direction, consider ring as closed
|
|
// (though closure is not important in this algorithm - any dupped
|
|
// point is skipped)
|
|
typedef detail::normalized_view<Ring const> view_type;
|
|
view_type view(ring);
|
|
|
|
typedef geometry::ever_circling_range_iterator<view_type const> it_type;
|
|
it_type previous(view);
|
|
it_type current(view);
|
|
current++;
|
|
|
|
std::size_t index = 1;
|
|
while (equals::equals_point_point(*current, *previous) && index < n)
|
|
{
|
|
current++;
|
|
index++;
|
|
}
|
|
|
|
if (index == n)
|
|
{
|
|
// All points are apparently equal
|
|
return true;
|
|
}
|
|
|
|
it_type next = current;
|
|
next++;
|
|
while (equals::equals_point_point(*current, *next))
|
|
{
|
|
next++;
|
|
}
|
|
|
|
// We have now three different points on the ring
|
|
// Walk through all points, use a counter because of the ever-circling
|
|
// iterator
|
|
for (std::size_t i = 0; i < n; i++)
|
|
{
|
|
int const side = side_strategy_type::apply(*previous, *current, *next);
|
|
if (side == 1)
|
|
{
|
|
// Next is on the left side of clockwise ring:
|
|
// the piece is not convex
|
|
return false;
|
|
}
|
|
|
|
previous = current;
|
|
current = next;
|
|
|
|
// Advance next to next different point
|
|
// (because there are non-equal points, this loop is not infinite)
|
|
next++;
|
|
while (equals::equals_point_point(*current, *next))
|
|
{
|
|
next++;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
};
|
|
|
|
|
|
}} // namespace detail::is_convex
|
|
#endif // DOXYGEN_NO_DETAIL
|
|
|
|
|
|
#ifndef DOXYGEN_NO_DISPATCH
|
|
namespace dispatch
|
|
{
|
|
|
|
template
|
|
<
|
|
typename Geometry,
|
|
typename Tag = typename tag<Geometry>::type
|
|
>
|
|
struct is_convex : not_implemented<Tag>
|
|
{};
|
|
|
|
template <typename Box>
|
|
struct is_convex<Box, box_tag>
|
|
{
|
|
static inline bool apply(Box const& )
|
|
{
|
|
// Any box is convex (TODO: consider spherical boxes)
|
|
return true;
|
|
}
|
|
};
|
|
|
|
template <typename Box>
|
|
struct is_convex<Box, ring_tag> : detail::is_convex::ring_is_convex
|
|
{};
|
|
|
|
|
|
} // namespace dispatch
|
|
#endif // DOXYGEN_NO_DISPATCH
|
|
|
|
// TODO: variants
|
|
|
|
// TODO: documentation / qbk
|
|
template<typename Geometry>
|
|
inline bool is_convex(Geometry const& geometry)
|
|
{
|
|
return dispatch::is_convex<Geometry>::apply(geometry);
|
|
}
|
|
|
|
|
|
}} // namespace boost::geometry
|
|
|
|
|
|
#endif // BOOST_GEOMETRY_ALGORITHMS_IS_CONVEX_HPP
|