Chris@102: // Boost.Geometry (aka GGL, Generic Geometry Library)
Chris@102: 
Chris@102: // Copyright (c) 2012-2014 Barend Gehrels, Amsterdam, the Netherlands.
Chris@102: 
Chris@102: // Use, modification and distribution is subject to the Boost Software License,
Chris@102: // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@102: // http://www.boost.org/LICENSE_1_0.txt)
Chris@102: 
Chris@102: #ifndef BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_JOIN_MITER_HPP
Chris@102: #define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_JOIN_MITER_HPP
Chris@102: 
Chris@102: #include <boost/assert.hpp>
Chris@102: #include <boost/geometry/core/cs.hpp>
Chris@102: #include <boost/geometry/policies/compare.hpp>
Chris@102: #include <boost/geometry/util/math.hpp>
Chris@102: #include <boost/geometry/util/select_most_precise.hpp>
Chris@102: 
Chris@102: #include <boost/geometry/strategies/buffer.hpp>
Chris@102: 
Chris@102: 
Chris@102: namespace boost { namespace geometry
Chris@102: {
Chris@102: 
Chris@102: namespace strategy { namespace buffer
Chris@102: {
Chris@102: 
Chris@102: /*!
Chris@102: \brief Let the buffer create sharp corners
Chris@102: \ingroup strategies
Chris@102: \details This strategy can be used as JoinStrategy for the buffer algorithm.
Chris@102:     It creates a sharp corners around each convex vertex. It can be applied
Chris@102:     for (multi)linestrings and (multi)polygons.
Chris@102:     If corners are sharp by themselves, the miters might become very long. Therefore
Chris@102:     there is a limit (miter_limit), in terms of the used distance, which limits
Chris@102:     their length. The miter is not changed to a bevel form (as done in some
Chris@102:     other software), it is just adapted to the specified miter_limit but keeps
Chris@102:     its miter form.
Chris@102:     If the buffer distance is 5.0, and the miter limit is 2.0, generated points
Chris@102:     will be located at a distance of at most 10.0 (2*5) units.
Chris@102:     This strategy is only applicable for Cartesian coordinate systems.
Chris@102: 
Chris@102: \qbk{
Chris@102: [heading Example]
Chris@102: [buffer_join_miter]
Chris@102: [heading Output]
Chris@102: [$img/strategies/buffer_join_miter.png]
Chris@102: [heading See also]
Chris@102: \* [link geometry.reference.algorithms.buffer.buffer_7_with_strategies buffer (with strategies)]
Chris@102: \* [link geometry.reference.strategies.strategy_buffer_join_round join_round]
Chris@102: }
Chris@102:  */
Chris@102: class join_miter
Chris@102: {
Chris@102: public:
Chris@102: 
Chris@102:     //! \brief Constructs the strategy
Chris@102:     //! \param miter_limit The miter limit, to avoid excessively long miters around sharp corners
Chris@102:     explicit inline join_miter(double miter_limit = 5.0)
Chris@102:         : m_miter_limit(valid_limit(miter_limit))
Chris@102:     {}
Chris@102: 
Chris@102: #ifndef DOXYGEN_SHOULD_SKIP_THIS
Chris@102:     //! Fills output_range with a sharp shape around a vertex
Chris@102:     template <typename Point, typename DistanceType, typename RangeOut>
Chris@102:     inline bool apply(Point const& ip, Point const& vertex,
Chris@102:                 Point const& perp1, Point const& perp2,
Chris@102:                 DistanceType const& buffer_distance,
Chris@102:                 RangeOut& range_out) const
Chris@102:     {
Chris@102:         geometry::equal_to<Point> equals;
Chris@102:         if (equals(ip, vertex))
Chris@102:         {
Chris@102:             return false;
Chris@102:         }
Chris@102:         if (equals(perp1, perp2))
Chris@102:         {
Chris@102:             return false;
Chris@102:         }
Chris@102: 
Chris@102:         typedef typename coordinate_type<Point>::type coordinate_type;
Chris@102:         typedef typename geometry::select_most_precise
Chris@102:         <
Chris@102:             coordinate_type,
Chris@102:             double
Chris@102:         >::type promoted_type;
Chris@102: 
Chris@102:         Point p = ip;
Chris@102: 
Chris@102:         // Check the distance ip-vertex (= miter distance)
Chris@102:         // (We calculate it manually (not using Pythagoras strategy) to reuse
Chris@102:         //  dx and dy)
Chris@102:         coordinate_type const dx = get<0>(p) - get<0>(vertex);
Chris@102:         coordinate_type const dy = get<1>(p) - get<1>(vertex);
Chris@102: 
Chris@102:         promoted_type const distance = geometry::math::sqrt(dx * dx + dy * dy);
Chris@102: 
Chris@102:         promoted_type const max_distance
Chris@102:             = m_miter_limit * geometry::math::abs(buffer_distance);
Chris@102: 
Chris@102:         if (distance > max_distance)
Chris@102:         {
Chris@102:             BOOST_ASSERT(distance != 0.0);
Chris@102: 
Chris@102:             promoted_type const proportion = max_distance / distance;
Chris@102:             set<0>(p, get<0>(vertex) + dx * proportion);
Chris@102:             set<1>(p, get<1>(vertex) + dy * proportion);
Chris@102:         }
Chris@102: 
Chris@102:         range_out.push_back(perp1);
Chris@102:         range_out.push_back(p);
Chris@102:         range_out.push_back(perp2);
Chris@102:         return true;
Chris@102:     }
Chris@102: 
Chris@102:     template <typename NumericType>
Chris@102:     inline NumericType max_distance(NumericType const& distance) const
Chris@102:     {
Chris@102:         return distance * m_miter_limit;
Chris@102:     }
Chris@102: 
Chris@102: #endif // DOXYGEN_SHOULD_SKIP_THIS
Chris@102: 
Chris@102: private :
Chris@102:     double valid_limit(double miter_limit) const
Chris@102:     {
Chris@102:         if (miter_limit < 1.0)
Chris@102:         {
Chris@102:             // It should always exceed the buffer distance
Chris@102:             miter_limit = 1.0;
Chris@102:         }
Chris@102:         return miter_limit;
Chris@102:     }
Chris@102: 
Chris@102:     double m_miter_limit;
Chris@102: };
Chris@102: 
Chris@102: }} // namespace strategy::buffer
Chris@102: 
Chris@102: 
Chris@102: }} // namespace boost::geometry
Chris@102: 
Chris@102: #endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_JOIN_MITER_HPP