c++ - 使用 boost::geometry 的多边形法线向量

Question

我正在尝试 boost::geometry 并且想知道您是否知道一种在多边形和线段之间的交点处获取多边形法向量的有效方法。或者类似于它相交的线段的线段标识？如果我有包含交叉点的多边形的线段，我确实了解如何获得法线。到目前为止我有

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>
#include <boost/assign.hpp>


int main(){


typedef model::d2::point_xy<double> point;
typedef model::ring< point > ring;
typedef model::polygon< point > polygon;
typedef model::multi_polygon< polygon > polygons;
typedef model::box< point > box;
typedef boost::geometry::model::segment<point> Segment

//Polygon
std::string poly_file="poly.dat";
polygon poly;
read_wkt(poly_file, poly);
correct(poly);

//Line segment:
polygon lineSegment;    
point p0(0,-0.5);
point p1(1,0.5);
append(lineSegment, p0);
append(lineSegment, p1);

//Getting intersection:
std::vector<point> output;
intersection(poly, lineSegment, output);

//Getting normal vector at this intersection point
// ???





   return 0;
}

提前非常感谢！