This demonstration graphs a function f(x,y) over a rectangular domain. By default, the domain is set to -1 ≤ x ≤ 1, -1 ≤ y ≤ 1 and the function is set to f(x,y) = x^2 - y^2.

In the window labeled Domain and Range, you can choose both the center and radius of a red disc domain in the xy-plane using the white and red hotspots respectively. The magenta line segment along the z-axis in this window shows the range of f(x,y) over the red disc domain