Chris@102: // Boost.Geometry (aka GGL, Generic Geometry Library)
Chris@102: 
Chris@102: // Copyright (c) 2012-2015 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_ROUND_HPP
Chris@102: #define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_JOIN_ROUND_HPP
Chris@102: 
Chris@102: #include <algorithm>
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/strategies/buffer.hpp>
Chris@102: #include <boost/geometry/util/math.hpp>
Chris@102: #include <boost/geometry/util/select_most_precise.hpp>
Chris@102: 
Chris@102: #ifdef BOOST_GEOMETRY_DEBUG_BUFFER_WARN
Chris@102: #include <boost/geometry/io/wkt/wkt.hpp>
Chris@102: #endif
Chris@102: 
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: \brief Let the buffer create rounded corners
Chris@102: \ingroup strategies
Chris@102: \details This strategy can be used as JoinStrategy for the buffer algorithm.
Chris@102:     It creates a rounded corners around each convex vertex. It can be applied
Chris@102:     for (multi)linestrings and (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_join_round]
Chris@102: [heading Output]
Chris@102: [$img/strategies/buffer_join_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_join_miter join_miter]
Chris@102: }
Chris@102:  */
Chris@102: class join_round
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:     explicit inline join_round(std::size_t points_per_circle = 90)
Chris@102:         : m_points_per_circle(points_per_circle)
Chris@102:     {}
Chris@102: 
Chris@102: private :
Chris@102:     template
Chris@102:     <
Chris@102:         typename PromotedType,
Chris@102:         typename Point,
Chris@102:         typename DistanceType,
Chris@102:         typename RangeOut
Chris@102:     >
Chris@102:     inline void generate_points(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:         PromotedType const dx1 = get<0>(perp1) - get<0>(vertex);
Chris@102:         PromotedType const dy1 = get<1>(perp1) - get<1>(vertex);
Chris@102:         PromotedType const dx2 = get<0>(perp2) - get<0>(vertex);
Chris@102:         PromotedType const dy2 = get<1>(perp2) - get<1>(vertex);
Chris@102: 
Chris@102:         PromotedType const two = 2.0;
Chris@102:         PromotedType const two_pi = two * geometry::math::pi<PromotedType>();
Chris@102: 
Chris@102:         PromotedType const angle1 = atan2(dy1, dx1);
Chris@102:         PromotedType angle2 = atan2(dy2, dx2);
Chris@102:         while (angle2 > angle1)
Chris@102:         {
Chris@102:             angle2 -= two_pi;
Chris@102:         }
Chris@102:         PromotedType const angle_diff = angle1 - angle2;
Chris@102: 
Chris@102:         // Divide the angle into an integer amount of steps to make it
Chris@102:         // visually correct also for a low number of points / circle
Chris@102: 
Chris@102:         // If a full circle is divided into 3 parts (e.g. angle is 125),
Chris@102:         // the one point in between must still be generated
Chris@102:         // The calculation below:
Chris@102:         // - generates 1 point  in between for an angle of 125 based on 3 points
Chris@102:         // - generates 0 points in between for an angle of 90  based on 4 points
Chris@102: 
Chris@102:         int const n = (std::max)(static_cast<int>(
Chris@102:             ceil(m_points_per_circle * angle_diff / two_pi)), 1);
Chris@102: 
Chris@102:         PromotedType const diff = angle_diff / static_cast<PromotedType>(n);
Chris@102:         PromotedType a = angle1 - diff;
Chris@102: 
Chris@102:         // Walk to n - 1 to avoid generating the last point
Chris@102:         for (int i = 0; i < n - 1; i++, a -= diff)
Chris@102:         {
Chris@102:             Point p;
Chris@102:             set<0>(p, get<0>(vertex) + buffer_distance * cos(a));
Chris@102:             set<1>(p, get<1>(vertex) + buffer_distance * sin(a));
Chris@102:             range_out.push_back(p);
Chris@102:         }
Chris@102:     }
Chris@102: 
Chris@102: public :
Chris@102: 
Chris@102: 
Chris@102: #ifndef DOXYGEN_SHOULD_SKIP_THIS
Chris@102:     //! Fills output_range with a rounded 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:         typedef typename coordinate_type<Point>::type coordinate_type;
Chris@102:         typedef typename boost::range_value<RangeOut>::type output_point_type;
Chris@102: 
Chris@102:         typedef typename geometry::select_most_precise
Chris@102:             <
Chris@102:                 typename geometry::select_most_precise
Chris@102:                     <
Chris@102:                         coordinate_type,
Chris@102:                         typename geometry::coordinate_type<output_point_type>::type
Chris@102:                     >::type,
Chris@102:                 double
Chris@102:             >::type promoted_type;
Chris@102: 
Chris@102:         geometry::equal_to<Point> equals;
Chris@102:         if (equals(perp1, perp2))
Chris@102:         {
Chris@102: #ifdef BOOST_GEOMETRY_DEBUG_BUFFER_WARN
Chris@102:             std::cout << "Corner for equal points " << geometry::wkt(ip) << " " << geometry::wkt(perp1) << std::endl;
Chris@102: #endif
Chris@102:             return false;
Chris@102:         }
Chris@102: 
Chris@102:         // Generate 'vectors'
Chris@102:         coordinate_type vix = (get<0>(ip) - get<0>(vertex));
Chris@102:         coordinate_type viy = (get<1>(ip) - get<1>(vertex));
Chris@102: 
Chris@102:         promoted_type length_i = geometry::math::sqrt(vix * vix + viy * viy);
Chris@102:         DistanceType const bd = geometry::math::abs(buffer_distance);
Chris@102:         promoted_type prop = bd / length_i;
Chris@102: 
Chris@102:         Point bp;
Chris@102:         set<0>(bp, get<0>(vertex) + vix * prop);
Chris@102:         set<1>(bp, get<1>(vertex) + viy * prop);
Chris@102: 
Chris@102:         range_out.push_back(perp1);
Chris@102:         generate_points<promoted_type>(vertex, perp1, perp2, bd, range_out);
Chris@102:         range_out.push_back(perp2);
Chris@102:         return true;
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: #endif // DOXYGEN_SHOULD_SKIP_THIS
Chris@102: 
Chris@102: private :
Chris@102:     std::size_t m_points_per_circle;
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_JOIN_ROUND_HPP