徐々に回転 Unity

http://answers.unity3d.com/questions/424048/lookrotation-weird-rotation.html
こちらを参考にした

    private Vector3 myDirection;

    public void Face(Vector3 direction)
    {
        myDirection = direction;
        //myTransform.rotation = Quaternion.LookRotation (direction);
        StopCoroutine("RunFace");
        StartCoroutine("RunFace");
    }

    public IEnumerator RunFace()
    {
        float speed = 9.1F;
        Quaternion rot = Quaternion.LookRotation(myDirection);

        while (true)
        {
            //Quaternion rot = Quaternion.LookRotation(transform.position - direction, Vector3.up);
            myTransform.rotation = Quaternion.Slerp(myTransform.rotation, rot, Time.deltaTime * speed);
            yield return 1;
        }
    }