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[英]How to calculate volume of solid of revolution of a polygon with boost::geometry?
[英]Create solid polygon in boost geometry
我是Boost幾何的新手,我用boost::geometry::assign_points()
創建了多邊形。 但是我只創建多邊形的外部和內部為空。 因此,我嘗試在B內部測試帶有兩個多邊形A,B和A的boost::geometry::overlaps()
,結果不重疊。
那么,我該怎么做才能創建實體多邊形(僅知道多邊形的外部點和多邊形的內部有效)?
根據定義,多邊形是實心的,直到減去內環為止。 從標准§6.1.11.1起:
多邊形是由1個外部邊界和0個或多個內部邊界定義的平面。 每個內部邊界在“多邊形”中定義一個孔。 三角形是具有3個不同的非共線頂點且沒有內部邊界的多邊形。 ¹
重疊並不意味着您認為的意思。
從§6.1.15.3起(基於DE-9IM的命名空間關系謂詞)
定義為
a.Overlaps(b) ⇔ ( dim(I(a)) = dim(I(b)) = dim(I(a) ∩ I(b))) ∧ (a ∩ b ≠ a) ∧ (a ∩ b ≠ b)
包含
a.Contains(b) ⇔ b.Within(a)
相交
a.Intersects(b) ⇔ ! a.Disjoint(b)
在你的情況,你可能會尋找!disjoint
, within
, contains
或intersection
:
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <iostream>
namespace bg = boost::geometry;
template <typename Geo> void debug(std::string name, Geo const& g) {
std::string reason;
std::cout << name << ": " << bg::dsv(g) << " " << bg::is_valid(g, reason) << ", '" << reason << "'\n";
}
template <typename Geo, typename F>
void both_ways(std::string name, Geo const& a, Geo const& b, F f) {
std::cout << name << "(a, b) -> " << f(a,b) << "\n";
std::cout << name << "(b, a) -> " << f(b,a) << "\n";
}
int main() {
std::cout << std::boolalpha;
using Pt = bg::model::d2::point_xy<int>;
using Poly = bg::model::polygon<Pt>;
using Multi = bg::model::multi_polygon<Poly>;
Poly const a {{ { 0,0 }, { 0,3 }, { 3,3 }, { 3,0 }, { 0,0 }} };
Poly const b {{ { 1,1 }, { 1,2 }, { 2,2 }, { 2,1 }, { 1,1 }} };
debug("a", a);
debug("b", b);
#define TEST(algo) both_ways(#algo, a, b, [](auto& a, auto& b) { return bg::algo(a, b); })
TEST(overlaps);
TEST(intersects);
TEST(within);
//TEST(contains); // contains(a,b) ⇔ within(b,a)
//TEST(crosses); // not implemented for polygons
TEST(disjoint);
both_ways("intersection", a, b, [](auto& a, auto& b) {
Multi c;
bg::intersection(a, b, c);
return boost::lexical_cast<std::string>(bg::dsv(c));
});
}
哪些印刷品
a: (((0, 0), (0, 3), (3, 3), (3, 0), (0, 0))) true, 'Geometry is valid'
b: (((1, 1), (1, 2), (2, 2), (2, 1), (1, 1))) true, 'Geometry is valid'
overlaps(a, b) -> false
overlaps(b, a) -> false
intersects(a, b) -> true
intersects(b, a) -> true
within(a, b) -> false
within(b, a) -> true
disjoint(a, b) -> false
disjoint(b, a) -> false
intersection(a, b) -> ((((1, 1), (1, 2), (2, 2), (2, 1), (1, 1))))
intersection(b, a) -> ((((1, 1), (1, 2), (2, 2), (2, 1), (1, 1))))
¹OGC簡單功能 /通用架構
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