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"Ross" <rli### [at] everestkc net> wrote:
> "PM 2Ring" <nomail@nomail> wrote in message
> news:web.42edf3bf208413009143b5c90@news.povray.org...
> > The catenary is the curve formed by a homogeneous chain suspended between
> > two points in a uniform gravity field. It looks like a parabola, but it's
> > mathematically quite different. The equation of a parabola is just
> > y = a*x*x, a simple quadratic, whereas a catenary is
> > y = a*cosh(x/a), a transcendental equation.
> >
> > I had occasion to look at Chris Colefax's chain building code in
> "Linc.inc",
> > after referring a new user to it, and was dismayed to discover that Chris
> > used quadratics to build his chains. :(
> >
> > The Chain() macro below constructs a true catenary. This is a preliminary
> > draft, so there are no docs as yet, sorry. Read the comments for hints. :)
> >
> > Any questions and comments are most welcome. Have fun!
>
> Cool cool. I think about this occasionally, probably everytime i see a
> cosh() for some reason. This is the same curve that would describe wires
> between telephone poles, right?
Yes, and catenary arches are very strong, too. Also, a catenary rotated
around the X-axis makes a catenoid, the shape of a soap-film between a pair
of parallel circular loops.
> anyway, neat work. i await the realistic glass render although the fake
> glass looked pretty too :)
Here's a more realistic one, with radiosity & dispersion. I'm doing one now
with photons; I assume it will take all weekend.
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