The window "Domain" displays a domain as a
wireframe, a point (u_{0}, v_{0}) 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 u_{0}, v_{0},
a, b, and c in the control
window.