void Update (){

    if(Input.GetMouseButton()){

        //从摄像机发出到点击坐标的射线

        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);

        RaycastHit hitInfo;

        if(Physics.Raycast(ray,out hitInfo)){

            //划出射线，只有在scene视图中才能看到

            Debug.DrawLine(ray.origin,hitInfo.point);

            GameObject gameObj = hitInfo.collider.gameObject;

            Debug.Log("click object name is " + gameObj.name);

            //当射线碰撞目标为boot类型的物品，执行拾取操作

            if(gameObj.tag == "boot"){

                Debug.Log("pickup!");

            }

        }

    }

}