Sorry Ken, but you got your maths wrong here.
The spheres are scaled and translated correctly to give the expected result.
Actually, they *do* give the correct and expected result!

I agree with GrimDude: It is a problem of perspective.

The camera is so close to the outer sphere, that the near part is
perspectively magnified so much, that it appears larger than the X/Y-plane
"equator" which lies farther back (and where the sphere really *do* meet at
the edges as expected.

I attached a screenshot from Moray where I recreated the scene and then
marked the actual equator with red and the *percieved* outer edge with
yellow (front, side, top and perspective view).

So long,
Johannes.

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Attachments:
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Preview of image 'spheres.gif'

Mike Metheny wrote:
> 
> Will someone please tell me why the following code renders as it does?


Try to use the orthographic camera which would eliminate the perspective
problem. If I remember correctly I have had this problem myself. The
solution is no good if you want the perspective, but it is good to use
when placing things in relation to eachother.

/Johan

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Johannes Hubert wrote:
> 
> Sorry Ken, but you got your maths wrong here.
> The spheres are scaled and translated correctly to give the expected result.
> Actually, they *do* give the correct and expected result!

  My math was 100% correct for what I wanted it to do. It was
my understanding of the original question that is at fault here.

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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>The camera is so close to the outer sphere, that the near part is
>perspectively magnified so much, that it appears larger than the X/Y-plane
>"equator" which lies farther back (and where the sphere really *do* meet at
>the edges as expected.
>


I was thinking of the set of solutions that satisfy a tangential line to the
point <-5,0,0> (assumed), but include the camera position. This set would be
null in that it cannot be satisfied from the current camera location, except
in orthographic projection (I think).

Perspective magnification, spherical aberration,....? Stymied...

Thanks for being agreeable. :)

GrimDude
vos### [at] arkansasnet

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>  My math was 100% correct for what I wanted it to do. It was
>my understanding of the original question that is at fault here.
>
>--
>Ken Tyler
>
>mailto://tylereng@pacbell.net

Yeah, the question wasn't very well put. Misleading in fact.

GrimDude
vos### [at] arkansasnet

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See? I managed to butcher the English language myself! :)

GrimDude wrote in message <371d7bb9.0@news.povray.org>...
>>The camera is so close to the outer sphere, that the near part is
>>perspectively magnified so much, that it appears larger than the X/Y-plane
>>"equator" which lies farther back (and where the sphere really *do* meet
at
>>the edges as expected.
>>
>
>
>I was thinking of the set of solutions that satisfy a tangential line to
the
>point <-5,0,0> (assumed), but include the camera position. This set would
be
>null in that it cannot be satisfied from the current camera location,
except
>in orthographic projection (I think).
>
>Perspective magnification, spherical aberration,....? Stymied...
>
>Thanks for being agreeable. :)
>
>GrimDude
>vos### [at] arkansasnet
>
>
>

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GrimDude <vos### [at] arkansasnet> wrote in message news:371d7f4a.0@news.povray.org...
> >  My math was 100% correct for what I wanted it to do. It was
> >my understanding of the original question that is at fault here.
> >
> >--
> >Ken Tyler
> >
> >mailto://tylereng@pacbell.net
>
> Yeah, the question wasn't very well put. Misleading in fact.


I disagree. It seemed quite clear to me..not at all misleading.


----------------------
Andy
------------------------------------------------------------------------------------------
-
--The Home Of Lunaland--
--visit my POV-Ray gallery--
--listen to my music--
www.acocker.freeserve.co.uk

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TIC, Andy. :) The author implied it was the coding that was in error. No big
deal.
I continue to get email on this, so here's an overhead view with a cylinder
marking a straight line from the original camera point to the point in
question.
-----------------------------------
camera { location <0,20,-6> direction z look_at <0,0,-6> }
light_source { <0,0,-12> color rgb 1 shadowless }

background { color rgb 1 }

sphere{<0,0,0>,5 pigment{rgbf<0,0,1,.5>}}
sphere{<0,0,0>,2.5 translate -2.5*x pigment{rgbt<1,1,0,.5>}}
sphere{<0,0,0>,2.5 translate 2.5*x pigment{rgbt<1,1,0,.5>}}

cylinder { <0,0,-12>,<-5,0,0>,.05 texture { pigment { color rgb
<1,0,0> } } }
---------------------------------------

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Attachments:
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Johannes Hubert wrote:

> Sorry Ken, but you got your maths wrong here.
> The spheres are scaled and translated correctly to give the expected result.
> Actually, they *do* give the correct and expected result!
>
> I agree with GrimDude: It is a problem of perspective.
>
> The camera is so close to the outer sphere, that the near part is
> perspectively magnified so much, that it appears larger than the X/Y-plane
> "equator" which lies farther back (and where the sphere really *do* meet at
> the edges as expected.
>
> I attached a screenshot from Moray where I recreated the scene and then
> marked the actual equator with red and the *percieved* outer edge with
> yellow (front, side, top and perspective view).
>
> So long,
> Johannes.
>
>  [Image]

Yep, it is a matter of perspective and visual abberation. A picture is worth a
thousand words:    <your spheres sliced in half>

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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<body text="#000000" bgcolor="#FFFFFF" link="#FF0000" vlink="#800080" alink="#0000FF">
Try moving the camera Waaaay back, and setting the angle down to 5 or so.
<p>camera{location<0,50,-250> look_at<0,0,0> angle 5}
<p>Here is an example of what I did, and what you did wrong.
<br> 
<p>--
<br>Bryan Valencia
<br>Software Services
<br><A HREF="http://www.209software.com">http://www.209software.com</A>
<br><A HREF="mailto:bry### [at] 209softwarecom">mailto:bry### [at] 209softwarecom</A>
<p>- "the gravest lie about Y2K matters, is that your company can,
<br>through the acquisition of affidavits of compliance, protect
<br>itself against harm, whether real or litigated. It can't.
<p>This faith in legal documents is hollow and in fact dangerous.
<br>The wisest course of action is for you to immediately disabuse
<br>yourself of this deceit."
<p>- from <A
HREF="http://language.perl.com/news/y2k.html">http://language.perl.com/news/y2k.html</A>
<br> 
</body>
</html>

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