private void OnAnimatorIK(int layerIndex)
    {
        AnimatorStateInfo info = my_ani.GetCurrentAnimatorStateInfo(1);
        if(info.IsName("r_hand"))
        {
            if (Vector3.Angle(transform.forward, Vector3.zero - transform.position) < 90)
            {
                my_ani.SetIKPositionWeight(AvatarIKGoal.RightHand, 1);//設定右手權重為1 表示全覆蓋
                my_ani.SetIKPosition(AvatarIKGoal.RightHand, Vector3.zero);//設定右手指向原點
            }
        }
    }