Question

这可能是多次询问的问题。但我交叉检查了类似的问题，以确保我的不再重复。

我有一个在代码中使用boost::geometry::intersection的源代码，用于获取两个多边形之间的交集结果。我对boost::geometry::correct测试了所用的多边形。多边形中的点序列是顺时针的。一切似乎都是正确的，但我从boost::geometry::intersection电话得到的输出不正确。

请帮我确定这里的问题。

这是类Point定义：

class Point {
public:
    double _x, _y;
    Point();
    Point(double, double);
    Point(const Point& orig);
    void SetX(double x);
    void SetY(double y);
    double GetX() const;
    double GetY() const;
};

使用boost库的代码

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/register/ring.hpp>
#include <boost/geometry/geometries/register/point.hpp>

BOOST_GEOMETRY_REGISTER_POINT_2D(Point, double, cs::cartesian, _x, _y)
BOOST_GEOMETRY_REGISTER_RING(std::vector<Point>)

namespace bg = boost::geometry;
namespace bd2 = boost::geometry::model::d2;

std::vector<Point> ORCAModel :: BoostPolyIntersect( std::vector<Point>& poly_1,
                                                    std::vector<Point>& poly_2,
                                                    bool &intersect_FLAG) const{

    std::vector<Point> poly_result;

    bg::correct(poly_1);
    bg::correct(poly_2);

    bg::intersection(poly_1, poly_2, poly_result);
    intersect_FLAG = (int(poly_result.size()) > 2)
    return poly_result;

    }

我使用基本的iostream来检查输出。（注意：输入值取自程序的一个运行顺序，但不作为用户输入输入）

--------------poly_1------------
( 0.075 : 27.2 )  ----  ( 27 : 27.2 )  ----  ( 27 : -22.8 )  ----  ( 0.075 : -22.8 )  ----  ( 0.075 : 27.2 )  ----  
--------------poly_2------------
( -23 : -22.8 )  ----  ( -23 : 3.925 )  ----  ( 27 : 3.925 )  ----  ( 27 : -22.8 )  ----  ( -23 : -22.8 )  ----  
result in bstpolyint size : 3
-----------------RESULT  POLY ------------------------
( 27 : 3.925 )  ----  ( 27 : -22.8 )  ----  ( 0.0750023 : 3.925 )  ----

输出应该有4个点，显然缺少一个点(0.07500 : - 22.8)。

（注意：在显示检查期间，输入点会四舍五入。尽管不是手动的。当在测试用例中使用显示的点时，结果是正确。但显然是因为四舍五入所使用的分数在原计划中进行计算并在测试用例中扰动。）

请帮助确定问题。提前谢谢。

编辑：这是我的测试用例。注释行polygon_1＆amp; polygon_2是舍入值。使用这些值可以得到新多边形的4个角。使用的放大值仅导致在释放模式中获得3个角。

#define BOOST_TEST_MODULE convexHull
#define BOOST_TEST_DYN_LINK
#include <boost/test/unit_test.hpp>

#include "../../geometry/Point.h"

#include <vector> 
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/register/ring.hpp>
#include <boost/geometry/geometries/register/point.hpp>
#include <string>

BOOST_GEOMETRY_REGISTER_POINT_2D(Point, double, cs::cartesian, _x, _y)
BOOST_GEOMETRY_REGISTER_RING(std::vector<Point>)

namespace bg = boost::geometry;
namespace bd2 = boost::geometry::model::d2;

BOOST_AUTO_TEST_SUITE(convexHull)

BOOST_AUTO_TEST_CASE(poly_Intersect_Test) {

//   std::vector<Point> polygon_1 = {Point(0.075, 27.2), Point( 27,  27.2), Point( 27, -22.8 ), Point( 0.075, -22.8 ), Point( 0.075,  27.2 )};
//   std::vector<Point> polygon_2 = {Point( -23, -22.8 ), Point( -23, 3.925 ), Point( 27, 3.925 ), Point( 27, -22.8 ), Point ( -23, -22.8 )};


  std::vector<Point> polygon_1 = {Point(749, 271999), Point(270000, 272000), Point(270000, -228000), Point(750, -227999), Point(749, 271999)};
  std::vector<Point> polygon_2 = {Point(-230000, -228000), Point (-230000, 39250) , Point(270000, 39250), Point (270000, -228000), Point (-230000, -228000)};
  std::vector<Point> polygon_result;

  bg::intersection(polygon_1, polygon_2, polygon_result);
  std::string points = "";
  for (auto it : polygon_result)
    points = points + "---" + it.toString();
  BOOST_CHECK_MESSAGE(false, points);
}

BOOST_AUTO_TEST_SUITE_END()

Answer 1

你没有交叉多边形，你正在传递 ring 。现在，问题在于您没有将正确的概念作为输出集合传递。

很简单，两个任意多边形（均匀环）可能有多个分离交叉多边形。您需要在输出类型中容纳多个交叉点。 @ cv_and_he进一步简化和扩展：

<强> Live On Coliru

#include <vector> 
#include <boost/geometry.hpp>
#include <boost/geometry/io/io.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/register/ring.hpp>
#include <boost/geometry/geometries/register/point.hpp>
#include <string>

class Point {
public:
    double _x, _y;
    Point():_x(),_y(){}
    Point(double x, double y):_x(x),_y(y){}
};

BOOST_GEOMETRY_REGISTER_POINT_2D(Point, double, cs::cartesian, _x, _y)
BOOST_GEOMETRY_REGISTER_RING(std::vector<Point>)

namespace bg = boost::geometry;

template <typename G>
void test(G const& g1, G const& g2) {
    std::cout << "----\nIntersecting\n\t" << bg::wkt(g1) << "\n\t" << bg::wkt(g2) << "\nresult: ";

    std::vector<G> polygon_results;
    bg::intersection<G, G>(g1, g2, polygon_results);

    for (auto polygon : polygon_results)
        std::cout << bg::wkt(polygon) << "\n";
}

int main() {
    using Ring = std::vector<Point>;

    test<Ring>(
            {{749,  271999},  {270000, 272000}, {270000, -228000},    {750, -227999},     {749,  271999}},
            {{-230000, -228000}, {-230000,  39250}, {270000,   39250}, {270000, -228000}, {-230000, -228000}});
    test<Ring>(
            {{0.075,   27.2},  { 27,   27.2}, { 27, -22.8 }, { 0.075, -22.8 }, { 0.075,  27.2 }},
            {{ -23, -22.8 }, { -23, 3.925 }, { 27, 3.925 },    { 27, -22.8 },   { -23, -22.8 }});
}

输出：

----
Intersecting
    POLYGON((749 271999,270000 272000,270000 -228000,750 -227999,749 271999))
    POLYGON((-230000 -228000,-230000 39250,270000 39250,270000 -228000,-230000 -228000))
result: POLYGON((270000 39250,270000 -228000,750 -227999,749.465 39250,270000 39250))
----
Intersecting
    POLYGON((0.075 27.2,27 27.2,27 -22.8,0.075 -22.8,0.075 27.2))
    POLYGON((-23 -22.8,-23 3.925,27 3.925,27 -22.8,-23 -22.8))
result: POLYGON((27 3.925,27 -22.8,0.075 -22.8,0.075 3.925,27 3.925))

Boost :: geometry :: intersection输出错误。版本BOOST_1_57_0

1 个答案: