平面と線分の交点を求める方法

#include <math.h> //平面の定義 class Plane { //ax+by+cz+d=0 public: double a,b,c,d; Plane(){} Plane(double a,double b,double c,double d){ this->a = a; this->b = b; this->c = c; this->d = d; } }; //ベクトルの定義 class Vector3D{ public: double x,y,z; Vector3D(){} Vector3D( double x, double y, double z) {this->x = x; this->y = y; this->z = z; } }; //頂点の定義(ベクトルと同じ) #define Vertex3D Vector3D //線分ABと平面の交点を計算する boo