UI始终朝向摄像机

    /// <summary>
    /// UI始终朝向摄像机
    /// tiShiPaiZi为UI，HTCeye为摄像机
    /// 此方法在Update里面调用
    /// </summary>
    public void LookCamera() {
        tiShiPaiZi.transform.forward = new Vector3(tiShiPaiZi.position.x - HTCeye.transform.position.x, 0, tiShiPaiZi.position.z - HTCeye.transform.position.z);
    }