The window "Domain" displays a domain and a point (u0, v0) in the domain.

The window "Surface: X(u, v)" shows the surface X(u, v), the point X(u0, v0), the tangent vectors Xu(u0, v0) and Xv(u0, v0) with their tails at X(u0, v0), the normal vector N(u0, v0), also with its tail at X(u0, v0), and the osculating paraboloid to X(u, v) at X(u0, v0).

The window "Projection" displays an alternate view of the display in the "Surface X(u, v)" window with X(u0, v0) as the origin, Xu(u0, v0) giving the direction of the x-axis, N(u0, v0) giving the direction of the z-axis, and N(u0, v0) x Xu(u0, v0) giving the direction of the y-axis.

The control window displays L11, L12, L21, L22, and L11L22 – L12L21. When L11L22 – L12L21 is positive, negative, or zero, the point X(u0, v0) will be elliptic, hyperbolic, or either parabolic or planar, respectively. The point X(u0, v0) will be planar if and only if all coefficients of the second fundamental form are 0. It is possible to change u0, v0, and X(u, v) in the control window.