
By creating an intersection of an origin-centered geodesic ball with the

-

plane in the Nil-space we get a geodesic sphere lying in

-

plane.
If

,
Now on this intersection we can use a translation defined by right multiplication by Heisenberg's matrix:
In the case

, this is the ordinary Euclidean translation in the

-

plane.
Finally, we rotate the sphere around the

axis with the following as

:
As we can see the

-translation changes the shape of the torus.
J. Szirmai, "The Densest Geodesic Ball Packing by a Type of Nil Lattices,"
Beiträge zur Algebra und Geometrie (Contributions to Algebra and Geometry),
48(2), 2007 pp. 383–397.