Unity3D計算點到線段的最短距離

float distanceFromSegment(Vector3 v1, Vector3 v2, Vector3 point){

    float xDis = v2.x-v1.x;
    float yDis = v2.y-v1.y;
    float zDis = v2.z-v1.z;
    float dx = point.x-v1.x;
    float dy = point.y-v1.y;
    float dz = point.z-v1.z;
    float d = xDis*xDis+yDis*yDis+zDis*zDis;
    float t = xDis*dx+yDis*dy+zDis*dz;//向量點積

    if(d>0){
        t/=d;
    }

    if(t<0){
        t=0;
    }else if(t>1){
        t=1;
    }
    dx = v1.x+t*xDis-point.x;
    dy = v1.y+t*yDis-point.y;
    dz = v1.z+t*zDis-point.z;
    return Mathf.Sqrt(dx*dx+dy*dy+dz*dz);

}