Select one of the cross-section shapes in the right-most panel. This will make visible the cross-section at the value of [math]x[/math] set by the "xcs" slider. Selecting the corresponding "Solid" check box will extend the solid formed by this cross-section from [math]x=a[/math] to [math]x=b[/math]. For the rectangular cross-section, the number in the box "H:W" is the aspect ratio (height to width).[br][br]It is possible (but not recommended) to turn on more than one cross-section shape at a time.[br][br]Click and drag the 3D panel in the center to change the view of the solid that is generated. You can choose the type of projection using the menu above the 3D view, to include red-cyan 3D glasses.