Camera cam;
    void Start ()
    {
       cam =this.GetComponent<Camera>();

    }

    void Update () {

        if (Input.GetMouseButtonDown())

        {

            TarRaycast();

        }

    }

    Vector3 mp ;//鼠标位置

    Transform targetTransform;//点选的物体

    public LayerMask targetingLayerMask;//指定射线能检测到的Layermask层

    private float targetingRayLength = Mathf.Infinity;//射线的长度

    public void TarRaycast()

    {

        targetingLayerMask.value =  << ; //不懂的看最下边的几颗栗子~

        mp = Input.mousePosition;

        targetTransform = null;

        if (cam != null)

        {

            RaycastHit hitInfo;

            Ray ray = cam.ScreenPointToRay(new Vector3(mp.x, mp.y, 0f));

            if (Physics.Raycast(ray.origin, ray.direction, out hitInfo, targetingRayLength, targetingLayerMask.value))

            {

                targetTransform = hitInfo.collider.transform;

            }

        }

        //得到被点选的物体后，对其进行操作~

        if (targetTransform != null)

        {

            Debug.Log(targetingLayerMask.value);

            Debug.Log(targetTransform.name);

        }

    }

}