"Renderdog" <slo### [at] hiwaaynet> wrote in message
news:web.417fb7a44c4748cbff5df6e40@news.povray.org...
> "David Robinson" <tdf### [at] ezrscom> wrote:
> > Can POV nativly build a helix that wraps around itself, to form a closed
> > loop? Imagine a helix following the path of a curve.
> >
> > All I need to specify is circle diameter, helix thickness and number of
> > twists (as well as the usual colour/texture etc).
> >
> > I expect this way to be a lot quicker, if it is supported...
>
> There is an isosurface called the Helical Torus that does
> what you're looking for. Some info on the parameters
> are available at this (very excellent!) resource provided
> by Mike Williams:
>
> http://www.econym.demon.co.uk/isotut/nfunc2.htm#ht
>
> Here are a couple of helical tori you can use as starting
> points. I used the following parameter values for thin rope
> trim around a window:
>
>  f_helical_torus(x,y,z, 100, 60, 2,
>          1.0, 1,
>          0.5,
>          0.25, 1, 1.0, 0)
>
> These parameters were for a thick rope around the base of
> a pillar:
>
>  f_helical_torus(x,y,z, 6.0, 8, 2,
>          0.5, 1,
>          0.5,
>          0.25, 1, 1.0, 0)
>
> Isosurfaces are not usually considered a newusers feature
> as they can be confusing, but once you get used to them
> they are much more powerful than normal csg objects.
>
> Also, if you need a mesh, I believe there are macros on
> Mike's website that convert isosurfaces to meshes, but
> I've not used them.
>
> For non-circular curves, you can draw a normal
> isosurface rope (f_helix1) along the path of a spline.
>
> -Mark Slone
>
>
Ah, thanks for the tip. Looks good - but I'm afraid I don't understand POV
enough yet to debug this:

Parse Error: Expected 'object or directive', function identifier found
instead

So, I'm assuming either my syntax is all wrong (I literally copy/pasted) or
I should have some #include files.

Sorry about this, I'll be off everybody's back soon :)

David

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