[buffer] add spheroid to buffer strategies as an optional constructor parameter

Author: barendgehrels

include/boost/geometry/strategies/geographic/buffer_end_round.hpp

@@ -37,6 +37,15 @@ class geographic_end_round
 {
 public :
 
+    //! \brief Constructs the strategy with a spheroid
+    //! \param spheroid The spheroid to be used
+    //! \param points_per_circle Number of points (minimum 4) that would be used for a full circle
+    explicit inline geographic_end_round(Spheroid const& spheroid,
+                                         std::size_t points_per_circle = default_points_per_circle)
+        : m_spheroid(spheroid)
+        , m_points_per_circle(get_point_count_for_end(points_per_circle))
+    {}
+
     //! \brief Constructs the strategy
     //! \param points_per_circle Number of points (minimum 4) that would be used for a full circle
     explicit inline geographic_end_round(std::size_t points_per_circle = default_points_per_circle)
@@ -133,8 +142,8 @@ public :
 #endif // DOXYGEN_SHOULD_SKIP_THIS
 
 private :
-    std::size_t m_points_per_circle;
     Spheroid m_spheroid;
+    std::size_t m_points_per_circle;
 };
 
 }} // namespace strategy::buffer

include/boost/geometry/strategies/geographic/buffer_join_miter.hpp

@@ -37,6 +37,15 @@ class geographic_join_miter
 {
 public :
 
+    //! \brief Constructs the strategy with a spheroid
+    //! \param spheroid The spheroid to be used
+    //! \param miter_limit The miter limit, to avoid excessively long miters around sharp corners
+    explicit inline geographic_join_miter(Spheroid const& spheroid,
+                                          double miter_limit = 5.0)
+        : m_spheroid(spheroid)
+        , m_miter_limit(valid_limit(miter_limit))
+    {}
+
     //! \brief Constructs the strategy
     //! \param miter_limit The miter limit, to avoid excessively long miters around sharp corners
     explicit inline geographic_join_miter(double miter_limit = 5.0)
@@ -112,8 +121,8 @@ private :
         return miter_limit;
     }
 
-    double m_miter_limit;
     Spheroid m_spheroid;
+    double m_miter_limit;
 };
 
 }} // namespace strategy::buffer

include/boost/geometry/strategies/geographic/buffer_join_round.hpp

@@ -37,6 +37,15 @@ class geographic_join_round
 {
 public :
 
+    //! \brief Constructs the strategy with a spheroid
+    //! \param spheroid The spheroid to be used
+    //! \param points_per_circle Number of points (minimum 4) that would be used for a full circle
+    explicit inline geographic_join_round(Spheroid const& spheroid,
+                                          std::size_t points_per_circle = default_points_per_circle)
+        : m_spheroid(spheroid)
+        , m_points_per_circle(get_point_count_for_join(points_per_circle))
+    {}
+
     //! \brief Constructs the strategy
     //! \param points_per_circle Number of points (minimum 4) that would be used for a full circle
     explicit inline geographic_join_round(std::size_t points_per_circle = default_points_per_circle)
@@ -102,8 +111,8 @@ public :
 #endif // DOXYGEN_SHOULD_SKIP_THIS
 
 private :
-    std::size_t m_points_per_circle;
     Spheroid m_spheroid;
+    std::size_t m_points_per_circle;
 };
 
 }} // namespace strategy::buffer

include/boost/geometry/strategies/geographic/buffer_point_circle.hpp

@@ -60,9 +60,18 @@ class geographic_point_circle
 {
 public :
 
+    //! \brief Constructs the strategy with a spheroid
+    //! \param spheroid The spheroid to be used
+    //! \param count Number of points (minimum 3) for the created circle
+    explicit inline geographic_point_circle(Spheroid const& spheroid,
+                                            std::size_t count = default_points_per_circle)
+        : m_spheroid(spheroid)
+        , m_count(get_point_count_for_circle(count))
+    {}
+
     //! \brief Constructs the strategy
     //! \param count Number of points (minimum 3) for the created circle
-    explicit geographic_point_circle(std::size_t count = default_points_per_circle)
+    explicit inline geographic_point_circle(std::size_t count = default_points_per_circle)
         : m_count(get_point_count_for_circle(count))
     {}
 
@@ -115,8 +124,8 @@ public :
 #endif // DOXYGEN_SHOULD_SKIP_THIS
 
 private :
-    std::size_t m_count;
     Spheroid m_spheroid;
+    std::size_t m_count;
 };
 
 }} // namespace strategy::buffer

include/boost/geometry/strategies/geographic/buffer_side_straight.hpp

@@ -43,6 +43,16 @@ template
 class geographic_side_straight
 {
 public :
+    //! \brief Constructs the strategy with a spheroid
+    //! \param spheroid The spheroid to be used
+    explicit inline geographic_side_straight(Spheroid const& spheroid)
+        : m_spheroid(spheroid)
+    {}
+
+    //! \brief Constructs the strategy
+    inline geographic_side_straight()
+    {}
+
 #ifndef DOXYGEN_SHOULD_SKIP_THIS
     // Returns true if the buffer distance is always the same
     static inline bool equidistant()

test/algorithms/buffer/Jamfile

@@ -30,6 +30,7 @@ test-suite boost-geometry-algorithms-buffer
     [ run buffer_multi_linestring_geo.cpp : : : <define>BOOST_GEOMETRY_TEST_ONLY_ONE_TYPE : algorithms_buffer_multi_linestring_geo ]
     [ run buffer_multi_polygon.cpp        : : : <define>BOOST_GEOMETRY_TEST_ONLY_ONE_TYPE : algorithms_buffer_multi_polygon ]
     [ run buffer_multi_polygon_geo.cpp    : : : <define>BOOST_GEOMETRY_TEST_ONLY_ONE_TYPE : algorithms_buffer_multi_polygon_geo ]
+    [ run buffer_geo_spheroid.cpp         : : : <define>BOOST_GEOMETRY_TEST_ONLY_ONE_TYPE : algorithms_buffer_geo_spheroid ]
     [ run buffer_linestring_aimes.cpp     : : : <define>BOOST_GEOMETRY_TEST_ONLY_ONE_TYPE : algorithms_buffer_linestring_aimes ]
     [ run buffer_linestring.cpp           : : : <define>BOOST_GEOMETRY_TEST_ONLY_ONE_TYPE <define>BOOST_GEOMETRY_ROBUSTNESS_ALTERNATIVE : algorithms_buffer_linestring_alternative ]
     [ run buffer_multi_linestring.cpp     : : : <define>BOOST_GEOMETRY_TEST_ONLY_ONE_TYPE <define>BOOST_GEOMETRY_ROBUSTNESS_ALTERNATIVE : algorithms_buffer_multi_linestring_alternative ]

test/algorithms/buffer/buffer_geo_spheroid.cpp

@@ -0,0 +1,80 @@
+// Boost.Geometry
+// Unit Test
+
+// Copyright (c) 2022 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)
+
+#include "test_buffer_geo.hpp"
+
+namespace
+{
+    int const points_per_circle = 360;
+    std::string const road = "LINESTRING(10.3966569 63.4276957,10.3998059 63.4279182,10.4000859 63.4283889,10.3982915 63.4284015,10.3980902 63.4288772,10.3987772 63.4288520)";
+    std::string const torg = "POINT(10.3937759 63.4302323)";
+}
+
+template <typename Formula, bool Clockwise, typename Point, typename Spheroid>
+void test_linestring(std::string const& label, Spheroid const& spheroid,
+                     double expected_area_round, double expected_area_miter)
+{
+    using linestring = bg::model::linestring<Point>;
+    using polygon = bg::model::polygon<Point, Clockwise>;
+
+    ut_settings settings(0.1);
+
+    bg::strategies::buffer::geographic<Formula, Spheroid> strategy(spheroid);
+    bg::strategy::buffer::geographic_side_straight<Formula, Spheroid> side(spheroid);
+    bg::strategy::buffer::geographic_join_miter<Formula, Spheroid> join_miter(spheroid);
+    bg::strategy::buffer::geographic_join_round<Formula, Spheroid> join_round(spheroid, points_per_circle);
+    bg::strategy::buffer::geographic_end_round<Formula, Spheroid> end_round(spheroid, points_per_circle);
+
+    // Ignored for linear or areal features
+    bg::strategy::buffer::geographic_point_circle<Formula, Spheroid> circle(spheroid, points_per_circle);
+
+    test_one_geo<linestring, polygon>(label + "_round", road, strategy, side, circle, join_round, end_round, expected_area_round, 10.0, settings);
+    test_one_geo<linestring, polygon>(label + "_miter", road, strategy, side, circle, join_miter, end_round, expected_area_miter, 10.0, settings);
+}
+
+template <typename Formula, bool Clockwise, typename Point, typename Spheroid>
+void test_point(std::string const& label, Spheroid const& spheroid, double expected_area)
+{
+    using polygon = bg::model::polygon<Point, Clockwise>;
+
+    ut_settings settings(0.01);
+
+    bg::strategies::buffer::geographic<Formula, Spheroid> strategy(spheroid);
+    bg::strategy::buffer::geographic_point_circle<Formula, Spheroid> circle(spheroid, points_per_circle);
+
+    // All are ignored for points
+    bg::strategy::buffer::geographic_side_straight<Formula, Spheroid> side(spheroid);
+    bg::strategy::buffer::geographic_join_miter<Formula, Spheroid> join_miter(spheroid);
+    bg::strategy::buffer::geographic_join_round<Formula, Spheroid> join_round(spheroid);
+    bg::strategy::buffer::geographic_end_round<Formula, Spheroid> end_round(spheroid);
+
+    test_one_geo<Point, polygon>(label, torg, strategy, side, circle, join_round, end_round, expected_area, 100.0, settings);
+}
+
+int test_main(int, char* [])
+{
+    BoostGeometryWriteTestConfiguration();
+
+    using test_type = default_test_type;
+
+    using point_t = bg::model::point<test_type, 2, bg::cs::geographic<bg::degree>>;
+
+    // Use the default spheroid
+    bg::srs::spheroid<test_type> def_spheroid;
+    test_linestring<bg::strategy::andoyer, true, point_t>("line_def", def_spheroid, 7996.0, 8093.0);
+    test_point<bg::strategy::andoyer, true, point_t>("point_def", def_spheroid, 31450.0);
+
+    // Call it with a quite different spheroid (a near sphere), this changes internal geographic calculations
+    // and should result in different areas. Using CSV creation, it's visible in QGis.
+    bg::srs::spheroid<test_type> alt_spheroid(6378000.0, 6375000.0);
+    test_linestring<bg::strategy::andoyer, true, point_t>("line_alt", alt_spheroid, 8097.0, 8115.3);
+    test_point<bg::strategy::andoyer, true, point_t>("point_alt", alt_spheroid, 31409.0);
+
+    return 0;
+}