"Jim Charter" <jrc### [at] msncom> wrote in message
news:400fd8f0$1@news.povray.org...

> Ah I get it now.

From Severi or from the image in binaries.images?

>  Divorse

Either you can't spell, or Dolly Parton has a lot of re-recording to do....

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Philippe Debar wrote:
> You could check POV-Ray 3.5/scenes/camera/shear.pov

Ah yes, I was going to point out applying a matrix to the camera. Didn't
know there was a sample scene for it though. That's neat. :)

Rune
--
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rune|vision:  http://runevision.com **updated Dec 30**
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"Rune" <run### [at] runevisioncom> wrote in message
news:400fee90$1@news.povray.org...
> Philippe Debar wrote:
> > You could check POV-Ray 3.5/scenes/camera/shear.pov
>
> Ah yes, I was going to point out applying a matrix to the camera. Didn't
> know there was a sample scene for it though. That's neat. :)
>

Gimme about 6 million years and I might understand how that works... IMHO Neo
had it easy.

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Tom Melly wrote:
> "Jim Charter" <jrc### [at] msncom> wrote in message
> news:400fd8f0$1@news.povray.org...
> 
> 
>>Ah I get it now.
> 
> 
> From Severi or from the image in binaries.images?

Both, I think, because you are doing exactly what I tried to explain ;) 
And that can be achieved at least by cropping (or rendering only a 
certain region), as you did in your example.

The trick is very useful when, for example, you try to take a photograph 
of a building.

1. If you level your camera and point it straight forward, you might not 
see the top portion of the building.

2. If you point the camera upwards, the building does not look 
rectangular anymore: all the lines start to "converge".

3. If you level your camera, point it straight forward (as in no 1.), 
and shift the film lower (maintaining the alignment) in relation to the 
lens, you will see the whole building with straigh walls that do not 
converge.

I posted 3 simple examples at p.b.i. They are all rendered so that the 
camera is allways at the same spot.

Severi Salminen

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"Severi Salminen" <sev### [at] NOT_THISsibafi> wrote in message
news:400ff433$1@news.povray.org...
>
> I posted 3 simple examples at p.b.i. They are all rendered so that the
> camera is allways at the same spot.

Nice examples. Did you crop* or use the camera-matrix method?

* either by post-process cropping or +sr etc switches

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Tom Melly wrote:

> 
> From Severi or from the image in binaries.images?
> 

Well it all came to me as I read the posts and each reinforcing each 
other.  Actually I originally had a glimpse of understanding but didn't 
want to believe it.  I admit is has some interesting associations, like 
looking obliquely from the window of a moving car.  The movement, road 
etc. seems to compel one sense of perspective while your eyes insist on 
another.

> 
>> Divorse
> 
> 
> Either you can't spell, or Dolly Parton has a lot of re-recording to do....
> 
> 
Yeah I thought it was wrong.  Still not sure how to fix it. "c" instead 
of "s"?  Gawd what a morning.  Divorce?  Want it? Fear it? Sure as hell 
can't spell it!  Let's write (right?) a song ourselves.

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Tom Melly wrote:
>>I posted 3 simple examples at p.b.i. They are all rendered so that the
>>camera is allways at the same spot.
> 
> 
> Nice examples. Did you crop* or use the camera-matrix method?
> 
> * either by post-process cropping or +sr etc switches

It was a simple post process crop. For the 3rd image I defined up 2*y 
and rendered using +h480 and cropped the correct portion.

Severi S.

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What is the problem ? Understanding shearing, the matrix or how to set 
up the camera ? If you know how you need to set up your camera vectors, 
you can do this directly and need not to use matrix.

Here is an example of a camera that automatically eliminates the 
vertical vanishing point :


camera{
   // Desc: Camera that eliminates vertical vanishing point
   // Date: 25 juillet 2002
   // Auth: Philippe Debar phd### [at] yahoofr

   #local Camera_Location = <-3,.01,-3>;
   /* as the standard "location" */

   #local Camera_Up       =  1 ;
   /* almost as the standard "up" : use a number (scalar) instead of a 
vector */

   #local Camera_Right    =  image_width/image_height ;
   /* almost as the standard "right" : use a number (scalar) instead of 
a vector  */

   #local Camera_Zoom     =  1 ;
   /*  almost as the standard "direction" : use a number (scalar) 
instead of a vector  */

   #local Camera_Look_At  = <-.5,2,.5> ;
   /* as the standard "look_at" */



   #ifndef(Shear_Trans) #include "transforms.inc" #end
   location 0
   up Camera_Up*y
   right Camera_Right*x
   direction
     vnormalize(
 
(Camera_Look_At.y-Camera_Location.y)/vlength((Camera_Look_At-Camera_Location)*<1,0,1>)*y
       + z
       )
     * Camera_Zoom
   Reorient_Trans(z, (Camera_Look_At-Camera_Location)*<1,0,1>)
   translate Camera_Location
}


You need to disable vista buffers to use this (option -uv).

I'll gladly explain anything that seems to be obscure.


Povingly,

Philippe


Tom Melly wrote:
> "Rune" <run### [at] runevisioncom> wrote in message
> news:400fee90$1@news.povray.org...
> 
>>Philippe Debar wrote:
>>
>>>You could check POV-Ray 3.5/scenes/camera/shear.pov
>>
>>Ah yes, I was going to point out applying a matrix to the camera. Didn't
>>know there was a sample scene for it though. That's neat. :)
>>
> 
> 
> Gimme about 6 million years and I might understand how that works... IMHO Neo
> had it easy.
> 
>

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"Philippe Debar" <phd### [at] wanadoobe> wrote in message
news:40104b84@news.povray.org...
> What is the problem ? Understanding shearing,

Yes - but I can at least see what it does (sort of - I don't really understand
why it helps so much with the perspective problem)

> the matrix

Yes - although, like quantum physics, it makes sense for about 5 mins after
reading that faq on 'em.

> or how to set up the camera ?

Yes - this is where I really get into trouble. I've read the docs on the camera
several times, and still can't get my head around the various options and how
they interact.

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Severi Salminen <sev### [at] NOT_THISsibafi> wrote in message
news:400ff433
> The trick is very useful when, for example, you try to take a photograph
> of a building.
>
> 1. If you level your camera and point it straight forward, you might not
> see the top portion of the building.
>
> 2. If you point the camera upwards, the building does not look
> rectangular anymore: all the lines start to "converge".
>
> 3. If you level your camera, point it straight forward (as in no 1.),
> and shift the film lower (maintaining the alignment) in relation to the
> lens, you will see the whole building with straigh walls that do not
> converge.


If this is what you trying for, John Guthkelch wrote a Field Camera Macro to
do exactly that. Search the older posts by author for Dr. John and you
should find it.  I used it in my IRTC architecture entry and it worked quite
well.

RG

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