In article <web.3d62b6ee2ffea3e6ee5540370@news.povray.org>,
 "JennyPage" <jen### [at] hotmailcom> wrote:

> Actually, I'm not that dumb!  I'm a Maths undergraduate writing a report on
> heat transfer.  I need a fairly simple illustration of a tea urn
> (commercial catering water boiler).
> 
> The tea urn is made of 1 layer of stainless steel and then 1 layer of
> polypropylene.
> 
> I tried to draw some cylinders but they seem to have zero width.  I could
> not find a way to draw cylinders with a substantial width.

By "width", do you mean thickness of the cylinder wall?
Shape surfaces are infinitely thin in POV, if you are using cylinders 
with "open" or "clipped_by" to remove the end caps you will get a single 
surface instead of a thick sheet. If you want a tube with some thickness 
to the walls, you should use a CSG difference of two cylinders:

difference {
    cylinder {< 0, 0, 0>, < 0, 1, 0>, 0.5}//the main cylinder
    //Cut out the center to leave a tube
    cylinder {< 0,-0.001, 0>, < 0, 1.001, 0>, 0.4}
}

Notice that the end points are slightly outside the main cylinder, this 
is to avoid precision errors where the surfaces would coincide.

If the polypropylene is thin enough that you can't see its thickness, 
you could get away with just texturing the inside differently. In that 
case, just give the first cylinder a stainless steel texture, and the 
second cylinder a polypropylene texture.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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