unity中世界坐标和绝对坐标之间的转换

public class TEST : MonoBehaviour {  void Start ()     {                Debug.Log(transform.position);}// Update is called once per framevoid Update ()     {        //绝对坐标转相对坐标       Vector3 vec= transform.InverseTransformPoint(transform.position);       Debug.Log(vec);//打印出来是（0，0，0）；与上面不一样        //相对坐标转绝对坐标       transform.TransformPoint(Vector3.up);}}