Hi Pilou,
The X, Y, and Z can be functions of u and v.
So X = sin(u) would be one example. Y = cos(v), Z = sqrt(something)...
Or more complex equations.

Check out the Macro's, which are likely from James:
mobius, offsetGrid, sineSurf, waveSurf, quadSpheres.

It would be nice to find a really cool example.
Maybe a curvy surface in 3d...

- Brian