...but i found a feature. I had a surface of revolution (sor) object, that
was generally the shape of a narrow column, slightly more narrow at the
base, widening to about 1.3 units at 3*y, and about a 1 unit radius at the
top, 11 units tall. if the camera was placed someplace between 0*y and 11*y
(the range the sor object extends) the sor would render incorrectly with an
area of the sor not rendered at the height of the camera. once the camera
was moved above or below the sor object, the object would render normally.
changing "look_at" had no effect on the outcome in either situation.

the feature i found was, use "sturm"! it fixed it in all cases.

I find it funny that the incorrectness when not using sturm was camera
height dependent.  Have other people noticed this? I don't consider it a
"bug" really, since pov has something to correct it already.

Also, I was curious why the default value of sturm is "off". Does it
significantly reduce speed in some cases?

thanks,
ross

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"Ross Litscher" <rli### [at] everestkcnet> wrote in message
news:4051f355$1@news.povray.org...
> ...but i found a feature. I had a surface of revolution (sor) object
>
> the feature i found was, use "sturm"! it fixed it in all cases.
>
> I find it funny that the incorrectness when not using sturm was camera
> height dependent.  Have other people noticed this? I don't consider it a
> "bug" really, since pov has something to correct it already.

It's fairly well known by the more avid users in these newsgroups. Was a
topic of discussion several times in the past.

> Also, I was curious why the default value of sturm is "off". Does it
> significantly reduce speed in some cases?

I hadn't noticed any significant impact on render times by using 'sturm on'.
It could probably be changed to be on by default and not be nough to worry
about, especially since it could then be done as 'sturm off' anyway. That
keyword dates back to the earliest versions when computers were slow and it
just stayed that way for the more recent versions. I'd guess that the
average CPU power has quadrupled since back then.

Also the blob, lathe, and torus are the other primitives I'd think might be
okay to default to use the Sturmian root solver. Not sure about prism, poly
though. Perhaps they could all be done the same way. In fact, thinking this
over it might even be prudent to make sturm a global setting.

-- 
Bob H.
http://www.3digitaleyes.com

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"Hughes, B." <omn### [at] charternet> wrote in message
news:405238d5$1@news.povray.org...
> "Ross Litscher" <rli### [at] everestkcnet> wrote in message
> news:4051f355$1@news.povray.org...
> >
> > I find it funny that the incorrectness when not using sturm was camera
> > height dependent.  Have other people noticed this? I don't consider it a
> > "bug" really, since pov has something to correct it already.
>
> It's fairly well known by the more avid users in these newsgroups. Was a
> topic of discussion several times in the past.
>

Interesting. I searched for a variety of things like "spline bug" and "sor
bug" i think, and didn't seem to find much. I'll go back and search some
more just to see what was said.

thanks for your insight,

ross.

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"Ross Litscher" <rli### [at] everestkcnet> wrote in message
news:40523a66$1@news.povray.org...
>
> "Hughes, B." <omn### [at] charternet> wrote in message
> news:405238d5$1@news.povray.org...
> >
> > It's fairly well known by the more avid users in these newsgroups. Was a
> > topic of discussion several times in the past.
>
> Interesting. I searched for a variety of things like "spline bug" and "sor
> bug" i think, and didn't seem to find much. I'll go back and search some
> more just to see what was said.

Let me see if I can help. I found these two threads through the web page
search:

http://news.povray.org/povray.beta-test.binaries/thread/%3C3bb13a69%40news.povray.org%3E/?ttop=184193&toff=50

http://news.povray.org/povray.general/thread/%3C40260cf3$1@news.povray.org%3E/

First is a whole different matter concerning the correctness of a surface of
revolution (fixed now?), second is very recent and about sturm *not* doing
better for the sor. I didn't have a great deal of luck finding exactly the
thing you experienced with the sor camera alignment artifact but I assure
you it had been talked about.

Bob H.

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