As far as I remember the control points for 
a lathe should be 2 dimensional. I.e. not 
3 dimensional as you have made them.

And are you sure about your selection of 
the first and last points and the in your 
quadratic_spline ?

Are you aware that these have special meanings ?

And be careful with points in the lathe that 
will "force" the "curve" to move into the 
negative side of the v-axis (i.e. "the left side").

I don't have time now to check your code or 
to explain more. Maybe tomorrow...


-- 
Best regards,

Tor Olav

mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


Stephane Nicolet wrote:
> 
> Hello,
> I was playing a little bit with the paragraph in the official
> documentation explaining quadratic splines for lathe objects, and I have
> encountered was seems (to me) to be a bug with the orthographic camera
> (see scene source below).I'm using PovRay 3.1g (official) and MacMegaPov
> 0.6 on a Macintosh, and the pb appears in both.
> 
> Can anybody else confirm this on other platforms? Or is it a well known
> problem? Or is it me who is doing something stupid ?
> 
> Cheers,
> Stephane.
> 
>  // this file seems to demonstrate a bug involving orthographic cameras
>  // and lathe objects with quadratic splines
>  // Bug shows up both in 3.1g official and MegaPov 0.6 unofficial
> 

... 8< ... Snip ... 8< ...

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