计算空间直线与平面的交点 （C#）

 public class NGlbVec3d
    {// 三维点
        public double x, y, z;
        public NGlbVec3d()
        {
        }
        public NGlbVec3d(double vx, double vy, double vz)
        {
            x = vx; y = vy; z = vz;
        }
        public static double operator *(NGlbVec3d a, NGlbVec3d b)
        {
            return (a.x * b.x + a.y * b.y + a.z * b.z);
        }
        public static NGlbVec3d operator -(NGlbVec3d a, NGlbVec3d b)
        {
            NGlbVec3d t = new NGlbVec3d();
            t.x = a.x - b.x;
            t.y = a.y - b.y;
            t.z = a.z - b.z;
            return t;                 
        }
        public static NGlbVec3d operator ^(NGlbVec3d a, NGlbVec3d b)
        {
            NGlbVec3d t = new NGlbVec3d();
            t.x = a.y*b.z - a.z*b.y;
            t.y = a.z*b.x - a.x*b.z;
            t.z = a.x*b.y - a.y*b.x;
            return t;
        }
        public void set(double vx, double vy, double vz)
        {
            x = vx; y = vy; z = vz;
        }
        public void normalize()
        {
           double t = Math.Sqrt(Math.Pow(x, 2) + Math.Pow(y, 2) + Math.Pow(z, 2));     
           if (t == 0.0) return;
           x = x / t;  y = y / t; z = z / t;
        }
    }
    public class NGlbPlane
    {// 平面
        public double A,B,C,D;
        public NGlbPlane()
        {

        }
        public NGlbPlane(double a, double b, double c, double d)
        {
            A = a; B = b; C = c; D = d;
        }
        public NGlbPlane(NGlbVec3d v1, NGlbVec3d v2, NGlbVec3d v3)
        {// 根据三个点计算平面方程 A,B,C,D
            NGlbVec3d v = (v3 - v1) ^ (v2 - v1);
            v.normalize();
            A = v.x;
            B = v.y;
            C = v.z;
            D = -(A * v1.x + B * v1.y + C * v1.z);
        }
    } 

// 计算线ln[2] 与平面plane[4]的交点 interPt
        private bool IsLineInterPlane(NGlbVec3d[] ln, NGlbPlane plane, NGlbVec3d interPt)             
        {
            // 直线方程P(t) = Q + tV
            NGlbVec3d Q = ln[0];
            NGlbVec3d V = ln[1] - ln[0];
            V.normalize();

            // 平面方程 N * P(x,y,z) + D = 0
            NGlbVec3d N = new NGlbVec3d(plane.A,plane.B,plane.C);
            //N.normalize();
            double D = plane.D;

            double s = N * V;

            if (s == 0.0) // 直线与平面平行
                return false;

            double q = - D - N * Q;
            double t = q / s;
            // 将t带入直线方程P(t) = Q + tV,就可得到直线与平面的交点
            interPt.x = Q.x + t * V.x;
            interPt.y = Q.y + t * V.y;
            interPt.z = Q.z + t * V.z;
            return true;
        }