The window "Domain" displays a domain as a wireframe, a point (u0, v0) in the domain, and the u-constant and v-constant curves through that point in red and green, respectively.

The window "Surface X(u,v)" shows the cone X(u,v) = (av*cos(u), bv*sin(u), cv) for the given domain and the images of the point and the curves from the "Domain" window.

It is possible to change u0, v0, a, b, and c in the control window.