By default,
only the outlines of the walls bounding the XY, XZ, and YZ axis planes
are shown. You can display filled walls by including the WALLDISPLAY=(FILL)
or WALLDISPLAY=(FILL OUTLINE) settings in the LAYOUT OVERLAY3D statement.
You can change the wall color (when filled) with the WALLCOLOR=option.
When filled, the wall lighting is adjusted to give a 3D effect, based
on the graph viewpoint.
layout overlay3d / cube=false
walldisplay=(fill) ;
surfaceplotparm x=height y=weight
z=density;
endlayout;