view3 is a tool for illustrating the connection between 3d graphs
and contour plots.  Run it from matlab by passing in a function
handle, or just run demo1, demo2, or demo3.

Drag across the 3d graph to rotate.  Move the scroll bar up and
down to change the level of the blue plane, whose intersection
with the graph is plotted in the upper right.  Press the button
to include the current level set in the contour plot in the
lower right.

Each of the demo files has an associated png file illustrating
its output.