在CGAL中,给定一条三维线段,如何计算该线段上距离某个端点已知距离的点?
Line_3<K> l = /* ... */;
Vector_3<K> v = l.to_vector();
Point_3<K> r = l.p + (d * d / v.squared_length()) * v;
l.p
部分是虚构的。)您可以减去您感兴趣的点以获得斜率向量,然后沿着它走。以下是一个 MWE:
// Compile with: clang++ -DBOOST_ALL_NO_LIB -DCGAL_USE_GMPXX=1 -O2 -g -DNDEBUG -Wall -Wextra -pedantic -march=native -frounding-math main.cpp -lgmpxx -lmpfr -lgmp
#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
using K = CGAL::Exact_predicates_exact_constructions_kernel;
using Point_3 = K::Point_3;
class InterPointInterpolator {
public:
InterPointInterpolator(const Point_3 &a, const Point_3 &b) : a(a), b(b) {}
// Returns points interpolated from a at t=0 to b at t=1
Point_3 operator()(const double t) const {
const auto m = b - a;
return a + t * m;
}
private:
Point_3 a;
Point_3 b;
};
int main(){
InterPointInterpolator ipi(Point_3(0, 0, 0), Point_3(10, 5, 20));
for(int i=0;i<=10;i++){
const auto interpolated_point = ipi(i/10.0);
std::cout<<interpolated_point<<std::endl;
}
return 0;
}
输出:
0 0 0
1 0.5 2
2 1 4
3 1.5 6
4 2 8
5 2.5 10
6 3 12
7 3.5 14
8 4 16
9 4.5 18
10 5 20