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_END_ROUND_HPP
Chris@102: #define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_END_ROUND_HPP
Chris@102: 
Chris@102: #include <boost/geometry/core/cs.hpp>
Chris@102: #include <boost/geometry/strategies/tags.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: #include <boost/geometry/io/wkt/wkt.hpp>
Chris@102: 
Chris@102: namespace boost { namespace geometry
Chris@102: {
Chris@102: 
Chris@102: 
Chris@102: namespace strategy { namespace buffer
Chris@102: {
Chris@102: 
Chris@102: 
Chris@102: /*!
Chris@102: \brief Let the buffer create rounded ends
Chris@102: \ingroup strategies
Chris@102: \details This strategy can be used as EndStrategy for the buffer algorithm.
Chris@102:     It creates a rounded end for each linestring-end. It can be applied
Chris@102:     for (multi)linestrings. Also it is applicable for spikes in (multi)polygons.
Chris@102:     This strategy is only applicable for Cartesian coordinate systems.
Chris@102: 
Chris@102: \qbk{
Chris@102: [heading Example]
Chris@102: [buffer_end_round]
Chris@102: [heading Output]
Chris@102: [$img/strategies/buffer_end_round.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_end_flat end_flat]
Chris@102: }
Chris@102:  */
Chris@102: class end_round
Chris@102: {
Chris@102: private :
Chris@102:     std::size_t m_points_per_circle;
Chris@102: 
Chris@102:     template
Chris@102:     <
Chris@102:         typename Point,
Chris@102:         typename PromotedType,
Chris@102:         typename DistanceType,
Chris@102:         typename RangeOut
Chris@102:     >
Chris@102:     inline void generate_points(Point const& point,
Chris@102:                 PromotedType alpha, // by value
Chris@102:                 DistanceType const& buffer_distance,
Chris@102:                 RangeOut& range_out) const
Chris@102:     {
Chris@102:         PromotedType const two = 2.0;
Chris@102:         PromotedType const two_pi = two * geometry::math::pi<PromotedType>();
Chris@102: 
Chris@102:         std::size_t point_buffer_count = m_points_per_circle;
Chris@102: 
Chris@102:         PromotedType const diff = two_pi / PromotedType(point_buffer_count);
Chris@102: 
Chris@102:         // For half circle:
Chris@102:         point_buffer_count /= 2;
Chris@102:         point_buffer_count++;
Chris@102: 
Chris@102:         for (std::size_t i = 0; i < point_buffer_count; i++, alpha -= diff)
Chris@102:         {
Chris@102:             typename boost::range_value<RangeOut>::type p;
Chris@102:             set<0>(p, get<0>(point) + buffer_distance * cos(alpha));
Chris@102:             set<1>(p, get<1>(point) + buffer_distance * sin(alpha));
Chris@102:             range_out.push_back(p);
Chris@102:         }
Chris@102:     }
Chris@102: 
Chris@102:     template <typename T, typename P1, typename P2>
Chris@102:     static inline T calculate_angle(P1 const& from_point, P2 const& to_point)
Chris@102:     {
Chris@102:         typedef P1 vector_type;
Chris@102:         vector_type v = from_point;
Chris@102:         geometry::subtract_point(v, to_point);
Chris@102:         return atan2(geometry::get<1>(v), geometry::get<0>(v));
Chris@102:     }
Chris@102: 
Chris@102: public :
Chris@102: 
Chris@102:     //! \brief Constructs the strategy
Chris@102:     //! \param points_per_circle points which would be used for a full circle
Chris@102:     //! (if points_per_circle is smaller than 4, it is internally set to 4)
Chris@102:     explicit inline end_round(std::size_t points_per_circle = 90)
Chris@102:         : m_points_per_circle((points_per_circle < 4u) ? 4u : points_per_circle)
Chris@102:     {}
Chris@102: 
Chris@102: #ifndef DOXYGEN_SHOULD_SKIP_THIS
Chris@102: 
Chris@102:     //! Fills output_range with a flat end
Chris@102:     template <typename Point, typename RangeOut, typename DistanceStrategy>
Chris@102:     inline void apply(Point const& penultimate_point,
Chris@102:                 Point const& perp_left_point,
Chris@102:                 Point const& ultimate_point,
Chris@102:                 Point const& perp_right_point,
Chris@102:                 buffer_side_selector side,
Chris@102:                 DistanceStrategy const& distance,
Chris@102:                 RangeOut& range_out) const
Chris@102:     {
Chris@102:         typedef typename coordinate_type<Point>::type coordinate_type;
Chris@102: 
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:         promoted_type const alpha = calculate_angle<promoted_type>(perp_left_point, ultimate_point);
Chris@102: 
Chris@102:         promoted_type const dist_left = distance.apply(penultimate_point, ultimate_point, buffer_side_left);
Chris@102:         promoted_type const dist_right = distance.apply(penultimate_point, ultimate_point, buffer_side_right);
Chris@102:         if (geometry::math::equals(dist_left, dist_right))
Chris@102:         {
Chris@102:             generate_points(ultimate_point, alpha, dist_left, range_out);
Chris@102:         }
Chris@102:         else
Chris@102:         {
Chris@102:             promoted_type const two = 2.0;
Chris@102:             promoted_type dist_half_diff = (dist_left - dist_right) / two;
Chris@102: 
Chris@102:             if (side == buffer_side_right)
Chris@102:             {
Chris@102:                 dist_half_diff = -dist_half_diff;
Chris@102:             }
Chris@102: 
Chris@102:             Point shifted_point;
Chris@102:             set<0>(shifted_point, get<0>(ultimate_point) + dist_half_diff * cos(alpha));
Chris@102:             set<1>(shifted_point, get<1>(ultimate_point) + dist_half_diff * sin(alpha));
Chris@102:             generate_points(shifted_point, alpha, (dist_left + dist_right) / two, range_out);
Chris@102:         }
Chris@102: 
Chris@102:         if (m_points_per_circle % 2 == 1)
Chris@102:         {
Chris@102:             // For a half circle, if the number of points is not even,
Chris@102:             // we should insert the end point too, to generate a full cap
Chris@102:             range_out.push_back(perp_right_point);
Chris@102:         }
Chris@102:     }
Chris@102: 
Chris@102:     template <typename NumericType>
Chris@102:     static inline NumericType max_distance(NumericType const& distance)
Chris@102:     {
Chris@102:         return distance;
Chris@102:     }
Chris@102: 
Chris@102:     //! Returns the piece_type (flat end)
Chris@102:     static inline piece_type get_piece_type()
Chris@102:     {
Chris@102:         return buffered_round_end;
Chris@102:     }
Chris@102: #endif // DOXYGEN_SHOULD_SKIP_THIS
Chris@102: };
Chris@102: 
Chris@102: 
Chris@102: }} // namespace strategy::buffer
Chris@102: 
Chris@102: }} // namespace boost::geometry
Chris@102: 
Chris@102: #endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_END_ROUND_HPP