[英]Boost geometry intersection does not output correctly
從以下代碼中,我計算出兩個多邊形的交點。 我希望如果不是多邊形,則輸出可以為NULL。 但是輸出為((((240,52.9999),(240,53),(240,53),(240,52.9999))))。 這不是多邊形。 有什么方法可以檢查輸出是否真的是多邊形?
#include <iostream>
#include <deque>
#include <vector>
#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/algorithms/append.hpp>
#include <algorithm> // for reverse, unique
#include <iostream>
#include <string>
int main()
{
typedef boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> point_2d;
typedef boost::geometry::model::polygon<point_2d> polygon_2d;
polygon_2d green;
boost::geometry::append(green, point_2d(286.188, 90.9575));
boost::geometry::append(green, point_2d(274.902, 56.2215));
boost::geometry::append(green, point_2d(274.238, 55.7393));
boost::geometry::append(green, point_2d(246.908, 51.9765));
boost::geometry::append(green, point_2d(194.477, 59.7441));
boost::geometry::append(green, point_2d(159.213, 101.141));
boost::geometry::append(green, point_2d(203.576, 149.537));
boost::geometry::append(green, point_2d(286.188, 90.9575));
polygon_2d blue;
boost::geometry::append(blue, point_2d(240, 53));
boost::geometry::append(blue, point_2d(240, -53));
boost::geometry::append(blue, point_2d(-60, -53));
boost::geometry::append(blue, point_2d(-60, 53));
boost::geometry::append(blue, point_2d(240, 53));
boost::geometry::correct(green);
boost::geometry::correct(blue);
std::vector<polygon_2d> output;
boost::geometry::intersection(green, blue, output);
std::cout << "green && blue:" << std::endl;
if(output.size())
{
std::cout<<boost::geometry::dsv(output[0])<<std::endl;
std::cout<<boost::geometry::area(output[0])<<std::endl;
}
return 0;
}
您可以清除無效的幾何圖形:
output.erase(
std::remove_copy_if(output.begin(), output.end(), output.begin(), [](polygon_2d const&g) { return boost::geometry::is_valid(g); }),
output.end());
現在,結果將為空。
對我來說很有趣的是,“無效”的幾何形狀將如何產生第一位置。 您可能已經知道,多邊形的選擇非常好:
讓我們放大一點:
現在,您可能會遇到一些浮點精度問題,就像是使用long long
點或提高多精度的同一實驗一樣,例如:
typedef boost::multiprecision::number<boost::multiprecision::cpp_bin_float<1024*128>> oopmh; // that's a lotta oomph
typedef boost::geometry::model::d2::point_xy<oopmh, boost::geometry::cs::cartesian> point_2d;
您會看到我們得到
green && blue:
(((2.4e+06, 530000), (-600000, 530000), (-600000, -530000), (2.4e+06, -530000), (2.4e+06, 530000)))
nan
所以看起來非常像我們只是獲得了一個奇異點。 如果您不希望這樣做,那么也許您應該只定義sorts的“ epsilon”值,即停止考慮重疊和重疊的閾值。
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