提升几何相交会产生奇怪的结果 [英] boost geometry intersection give strange results

问题描述

我想使用带有线和多边形的增强几何图形的交集函数.我希望交点是位于多边形内部的线的一部分.

I want to use the intersection function from boost geometry with a line and a polygon. I expect that the intersection is the part of the line which lies inside the polygon.

不幸的是，增强几何会返回位于多边形外部的线的一部分.这是Boost几何中的错误还是我的代码有问题?

Unfortunately boost geometry returns the part of the line which lies outside of the polygon. Is this a bug in boost geometry or is something wrong with my code?

#include <boost/geometry/core/cs.hpp>
#include <boost/geometry/geometries/point.hpp>
#include <boost/geometry/geometries/ring.hpp>
#include <boost/geometry/geometries/box.hpp>
#include <boost/geometry/geometries/segment.hpp>
#include <boost/geometry/geometries/linestring.hpp>
#include <boost/geometry/multi/geometries/multi_point.hpp>
#include <boost/geometry/multi/geometries/multi_linestring.hpp>
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <boost/geometry/algorithms/intersection.hpp>

namespace bg = boost::geometry;

using value_type = double ;
using cs_type = bg::cs::cartesian;
using point_type = bg::model::point< value_type , 2 , cs_type >;
using polygon_type = bg::model::ring< point_type > ;
using line_string_type = bg::model::linestring< point_type >;
using multi_line_type = bg::model::multi_linestring< line_string_type >;

int main( int argc , char *argv[] )
{
    line_string_type line;
    line.push_back( point_type { 13.37688020921095 , 53.66231710654281 } );
    line.push_back( point_type { 13.3857295713429 , 53.6636835518369 } );
    line.push_back( point_type { 13.39213495232734 , 53.66501934623722 } );
    line.push_back( point_type { 13.39719615524716 , 53.66546436809296 } );
    line.push_back( point_type { 13.40724694386097 , 53.66240690770171 } );

    polygon_type polygon;
    polygon.push_back( point_type { 13.35 , 53.64 } );
    polygon.push_back( point_type { 13.39 , 53.64 } );
    polygon.push_back( point_type { 13.39 , 53.68 } );
    polygon.push_back( point_type { 13.35 , 53.68 } );
    polygon.push_back( point_type { 13.35 , 53.64 } );

    multi_line_type intersection;
    bg::intersection( line , polygon , intersection );

    return 0;
}

推荐答案

确保您的输入几何满足记录的前提条件.

Make sure your input geometries satisfy the pre-conditions documented.

您可以使用bg::correct解决大多数问题(例如，多边形中点的正确CCW排序，关闭未封闭的多边形等):

You can use bg::correct to fix most issues (such as proper CCW ordering of points in the polygon, closing unclosed polygons etc.):

在Coliru上直播

#include <boost/geometry/core/cs.hpp>
#include <boost/geometry/geometries/point.hpp>
#include <boost/geometry/geometries/ring.hpp>
#include <boost/geometry/geometries/box.hpp>
#include <boost/geometry/geometries/segment.hpp>
#include <boost/geometry/geometries/linestring.hpp>
#include <boost/geometry/multi/geometries/multi_point.hpp>
#include <boost/geometry/multi/geometries/multi_linestring.hpp>
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <boost/geometry/algorithms/intersection.hpp>

namespace bg = boost::geometry;

using value_type       = double;
using cs_type          = bg::cs::cartesian;
using point_type       = bg::model::point<value_type, 2, cs_type>;
using polygon_type     = bg::model::ring<point_type>;
using line_string_type = bg::model::linestring<point_type>;
using multi_line_type  = bg::model::multi_linestring<line_string_type>;

int main()
{
    line_string_type line;
    line.push_back(point_type{13.37688020921095, 53.66231710654281});
    line.push_back(point_type{13.3857295713429,  53.6636835518369});
    line.push_back(point_type{13.39213495232734, 53.66501934623722});
    line.push_back(point_type{13.39719615524716, 53.66546436809296});
    line.push_back(point_type{13.40724694386097, 53.66240690770171});
    bg::correct(line);

    polygon_type polygon;
    polygon.push_back(point_type{13.35, 53.64});
    polygon.push_back(point_type{13.39, 53.64});
    polygon.push_back(point_type{13.39, 53.68});
    polygon.push_back(point_type{13.35, 53.68});
    polygon.push_back(point_type{13.35, 53.64});
    bg::correct(polygon);

    multi_line_type intersection;
    bg::intersection(line, polygon, intersection);

    std::cout << bg::wkt(intersection);
}

此打印

MULTILINESTRING((13.3769 53.6623,13.3857 53.6637,13.39 53.6646))

在未输入correct的情况下，它将打印以下内容:

With the input un-corrected it would have printed this instead:

MULTILINESTRING((13.39 53.6646,13.3921 53.665,13.3972 53.6655,13.4072 53.6624))

这篇关于提升几何相交会产生奇怪的结果的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！