월드 오브젝트의 좌표를 NGUI 좌표로 변환

http://www.unitystudy.net/bbs/board.php?bo_table=writings&wr_id=92&sca=GUI

else if (ARROW_UID.Contains(currentTutoUID))
        {
            // 몬스터 위치에 정확한 좌표 찍기 위한 하드코딩.
            GameObject g = GameObject.FindGameObjectWithTag("Monster");
            Vector3 p = Camera.main.WorldToViewportPoint(g.transform.position);
            p = UICamera.mainCamera.ViewportToWorldPoint(p);
            btnArrow.transform.position = p;
            setActiveTarget(btnArrow.gameObject, true);
        }