Matthew Peters wrote:
> 
> I have a gear creation include file that i'm trying to make do bevel
> gears, the trouble is that when ever i make the points for a conic_sweep
> prism, they seem to be scaled to be slightly bigger(1.1?) in x/z... this
> trouble doesn't exist when i'm making a linear_sweep of the exact same
> values... is there some settings or an error that isn't documented? or
> does anyone have the scale factor?
> 
> If there is alot of interest in this code, i might release it... but i'm
> not sure yet...
> 
> also... has anybody made a rope include file that can make a sertain
> length of rope between two points that are not level?
> I have all the math, but can't seem to solve it...
> (anybody know how to solve n=sinh(z)/z for z?)

What size are your gears?  I've just run a quick test using circular
points with a radius of around 1 unit, and both the linear and conic
sweeps are equal sizes in all dimensions.  However, problems with very
small object co-ordinates have been reported in the past...

As for the hanging cable question, I have to admit I've also been unable
to discover the answer (analytically, at least).  Therefore, at the
moment I can see two possible solutions: using approximation to find the
necessary 'droop factor' to give a desired catenary-segment length
(within a certain tolerance) or simulating the cable as a series of
linked springs.

The first option is probably quite feasible under POV-Ray 3.1 - I've
just created macros to reparameterize cubic splines by arc-length
(allowing constant length along the spline path regardless of shape),
and the sampling/interpolation performance seems to be quite acceptable
(and far faster than would have been possible under POV-Ray 3.0).

The second option (similar to the spring simulations described so
excellently by Hugo Elias) would also allow simulating cables with only
one end fixed (swinging pony-tails, etc.), variable masses along the
cable (eg. a necklace with a heavy pendant), and more.

I hope to be testing both methods soon, so that I can release a properly
updated version of my Link include file.  Some have suggested including
this as a feature of the POV-Ray Spline System I am working on at the
moment (so splines could have gravity forces applied to them), and it
might even be an idea to get both methods up and running...

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