还以为出错了，仔细看发现ToString()自动四舍五入

 

 

 

 

            Vector3 forward = Camera.main.transform.forward;

            Debug.Log("forward:" + forward.x.ToString() + "," +

                                   forward.y.ToString() + "," +

                                   forward.z.ToString() +

                     " forward * 2:" + (forward * 2).x.ToString() + "," +

                                       (forward * 2).y.ToString() + "," +

                                       (forward * 2).z.ToString()

                     );

            gameObject.transform.position = Camera.main.transform.position +

                forward * 2;