物体根据鼠标点击拖动物体移动

    private GameObject target;
    private bool isMouseDrag;//判断是否有物体
    private Vector3 screenPosition;//屏幕坐标 


  public void MoverGameObject()
    {
        if (Input.GetMouseButtonDown(0))
        {
           
            Ray r = Camera.main.ScreenPointToRay(Input.mousePosition);
            RaycastHit hit;

            if (Physics.Raycast(r, out hit))
            {
                target = hit.collider.gameObject; 
                isMouseDrag = true;
                screenPosition = Camera.main.WorldToScreenPoint(target.transform.position);//世界坐标转为屏幕坐标                                                                                           
            }
        }
        if (Input.GetMouseButtonUp(0))
        {
            isMouseDrag = false;
        }

        if (isMouseDrag)
        {
            Vector3 v = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPosition.z);
            Vector3 worldPostion = Camera.main.ScreenToWorldPoint(v);
            target.transform.position = new Vector3(worldPostion.x, worldPostion.y, worldPostion.z);
        }
    }