已知空间两点组成的直线求线上某点的Z值

#include<iostream>

using namespace std;

//三维double矢量
struct Vec3d
{
    double x, y, z;

    Vec3d()
    {
        x = 0.0;
        y = 0.0;
        z = 0.0;
    }
    Vec3d(double dx, double dy, double dz)
    {
        x = dx;
        y = dy;
        z = dz;
    }
    void Set(double dx, double dy, double dz)
    {
        x = dx;
        y = dy;
        z = dz;
    }
};

bool CalLinePointZ(const Vec3d & v1, const Vec3d & v2, Vec3d & vp)
{
    const double eps = 0.0000001;

    //方向向量
    Vec3d s(v2.x-v1.x, v2.y - v1.y, v2.z - v1.z);

    //此时无法求值
    if (abs(s.x) == eps && abs(s.y) == eps)
    {
        return false;
    }

    double t = 0;
    if (abs(s.x) > eps && abs(s.y) == eps)
    {
        double t = (vp.x - v1.x) / s.x;
    }
    else if (abs(s.x) == eps && abs(s.y) > eps)
    {
        double t = (vp.y - v1.y) / s.y;
    }
    else
    {
        double tx = (vp.x - v1.x) / s.x;
        double ty = (vp.y - v1.y) / s.y;

        //说明点不可能在直线上
        if (abs(tx - ty) > eps)
        {
            return false;
        }
        t = tx;
    }

    vp.z = t * s.z + v1.z;
    return true;
}

int main()
{
    Vec3d v1(0.0, 0.0, 3.7);
    Vec3d v2(5.0, 5.0, 4.5);

    Vec3d vp;
    vp.x = 4.6;
    vp.y = 4.6;
    vp.z = 0.0;

    if (CalLinePointZ(v1, v2, vp))
    {
        cout << "该点的高程：" << vp.z << endl;
    }

    return 0;
}