Unity3D 屏幕坐标跟世界坐标的转换

using UnityEngine;using System.Collections; public class cameramove : MonoBehaviour{     private Vector3 world;     private float speed = 0;//物体移动的速度     // Use this for initialization    void Start()    {        world.x = -2;        world.y = 0;        world.z = 6;    }     // Update is called once per frame    void Update()    {        Vector2 screenpos = Camera.main.WorldToScreenPoint(transform.position);//物体的世界坐标转化成屏幕坐标        Vector3 e = Input.mousePosition;//鼠标的位置                  //当点击鼠标中键时         if (Input.GetMouseButtonDown(2))        {            //e.z=screenpos.z;//1.因为鼠标的屏幕 Z 坐标的默认值是0，所以需要一个z坐标            //e.z=1;//将鼠标            //摄像机要垂直于x-z平面            //world=Camera.main.ScreenToWorldPoint(e);            world = new Vector3(Input.mousePosition.x/Screen.width,Input.mousePosition.y/Screen.height,106f );            Vector3 world1= Camera.main.ViewportToWorldPoint(new Vector3(world.x, world.y, 106f));            //world.x = Camera.main.ScreenToWorldPoint(Input.mousePosition).x;            //world.z = Camera.main.ScreenToWorldPoint(Input.mousePosition).y;            //world.y = transform.position.y;             print("new x:" + world.x);            print("new y:" + world.y);            print("new z:" + world.z);             //创建物体            //GameObject goNew = GameObject.CreatePrimitive(PrimitiveType.Sphere);            //goNew.transform.position = world1;            transform.LookAt(world1);        }    }}