This is driving me crazy; I can't find an answer anywhere in the VIZ
help or on the internet.  All I want to do is turn a spline into a
surface and then extrude it.  I.e. I have a spline (a floor plan), and
I can extrude it, but the walls that are created are hollow.  So I
think I need to derive a surface from the spline, and extrude that, so
that I get solid walls (which is important because I'm subtracting
windows).  Can anyone help, or even suggest where on the net I could
get an answer?  Experts Exchange doesn't seem to have a VIZ section,
far as I can tell.  Thanks.