Drag the cursor across the window using the mouse button and keyboard strokes
assigned to the Arc Ball function.
The further the pointer is from the center of the window when dragging begins,
the finer the control. As the pointer moves, the graphic is pulled around the
center point. The axis of rotation is the line passing through the center point,
perpendicular to the line created by the center point and the current mouse
location, within the plane of the screen.