Thorsten Froehlich <tho### [at] trfde> wrote:

> > 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 ?
> 
> Try adding the "sturm" keyword to the lathe object.
>       Thorsten

Thanks, it was indeed a problem with the accuracy of the PovRay solver,
apparently, and the Sturmian solver works OK without being really slower
(rendering time is 30 sec vs. 27 sec). Now the fact that the results are
so unexpected suggests that 
a) PovRay *should* maybe switch automatically to the Sturmian solver for
quadratic spline lathes
b) or (at least) we could add a note in the beginning of the "advanced
shapes" of the documentation about the dangers of the default
intersection solver, and a pointer to the sturm keyword paragraph.

Stephane.

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