public Quaternion Interpolate(float fac, ref InvQuaternion16 v1, ref InvQuaternion16 v2)
        {
            var        q1 = v1.ToQuaternion();
            var        q2 = v2.ToQuaternion();
            Quaternion ret;

            Quaternion.Slerp(ref q1, ref q2, fac, out ret);
            return(ret);
        }
 public Quaternion Interpolate(ref InvQuaternion16 v1)
 {
     return(v1.ToQuaternion());
 }