"Chris Colefax" <chr### [at] tagpovrayorg> wrote in message
news:3e4863f5@news.povray.org...
>
> The problem you are seeing is caused by the method used to calculate the
> normal vector of the spline (required to orient the torus segments used to
> create the coil).  The current macro file is hardwired to use a 'sky'
vector
> of z to calculate the spline normal, and when the spline runs directly
along
> this axis a shift in orientation occurs.
>
> To fix the problem, you can ensure the spline doesn't run along the
z-axis,
> or download an updated version of the macro file (from
> www.geocities.com/ccolefax/spline), which will allow you to adjust the sky
> vector used with the spline_normal_sky option.

A big thank you, Chris. As simple an explanation as you make your files seem
(until looking at them!). I was so close to the answer, I tried the
spline_normal_sky once because that was one of the things I thought might
have to do with this (axis shifting) but I obviously used it wrong and saw
no change. Then again, I've now tried the suggested fix and it still isn't
going right. I just redownloaded the spline macro to be sure I have the
right file and retried and it's okay. However, in both files there is a
_SP_normsky which apparently uses y, not z. I won't try to figure it out
since it boggles my mind anyhow.

Bob

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