> We all know that perspective projection is for projecting on a flat
> surface, and that the perspective reference point is at the center.
> But what if you want to make 'perfect' cross-eyed stereo renderings,
> like me?
> 
> First, you need some input values and math to position the camera
> correctly. The math instantly shows that the perspective reference
> point isn't at the center, not even inside the image. So how are you
> going to do that in POV-Ray?

> I'd suggest a customizable reference point offset in 2D from the
> center, and in 3D like the focal point (NOT doing pointless FOV
> correction). For now, does anyone know a more straightforward way?

Are you trying to emulate things like 6x9 photo (with bascule (seesaw ?)
and vertical/horizontal movement of the lens ?).

Or am I totally misleaded ?

Wasn't there a patch for a user-defined camera somewhere ?


-- 




l'habillement, les chaussures que le maquillage et les accessoires.

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> We all know that perspective projection is for projecting on a flat
> surface, and that the perspective reference point is at the center. But
> what if you want to make 'perfect' cross-eyed stereo renderings, like
> me?

I create stereoscopic rendering "all the time" using PovRay, 
indeed some of the content is for this
   http://www.vroom.org.au
   http://astronomy.swin.edu.au/~pbourke/stereographics/vroom/
but also for daily visualisation. The basic approach I use 
involves image trimming, it is easy to set up a processing
pipline to deal with this. See
   http://astronomy.swin.edu.au/~pbourke/povray/raystereo/

-- 
Paul Bourke
pdb_NOSPAMswin.edu.au

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Slime wrote:
> > > The perspective reference point is the point perspective stuff is based
> > > on. So everything else you said didn't help me at all. :-( Maybe I can
> > > render a few examples tomorrow.
> >
> > Do you mean the vanishing point?
>
> Oh, ok. I looked it up and I see that the perspective reference point is the
> location of the camera.

Good idea to look it up. :-) There are several ways to see
the reference point, but I had to come up with a name.

> It should be possible to use the method I described nonetheless; by skewing
> the direction the camera is looking in, and then translating the camera the
> opposite amount, you will have essentially moved the camera location (the
> perspective reference point) without moving the image plane.

Somehow I feel it is impossible to do this right, but I don't know much
about the matrix. Google isn't very helpful because of another matrix.

Jonathan

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In article <web.4177a747cdaafef5d114d2650@news.povray.org>,
 "Jonathan" <nomail@nomail> wrote:

> Somehow I feel it is impossible to do this right,

here's another link to look at
http://www.cip.physik.uni-muenchen.de/~wwieser/render/stereo/create.html
has pov code

Also, about the look_at point. I had a friend that was very much into 
stereo photographs. When I was making some he said it's better to not 
have the camera point at something but should be looking out parallel, 
causes less eye strain. There were lots of other technical info he had 
but this is the only that stuck with me. I just shift the camera to the 
side keeping it parallel and compose those two images. Our brains are 
always working with distorted input, it's used to things being different 
sizes etc. -laz

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On Wed, 20 Oct 2004 18:00:45 EDT, "Jonathan" <nomail@nomail> wrote:
> I'd suggest a customizable reference point offset in 2D from the center,
> and in 3D like the focal point (NOT doing pointless FOV correction). For
> now, does anyone know a more straightforward way?

I'm not sure if that could be helpful in this case but I remember small macros
I wrote in addition to standard screen.inc include file two years ago, where
you can reference points from 3D<->2D, see:

From: Włodzimierz ABX Skiba <abx### [at] babilonorg>
Newsgroups: povray.text.scene-files
Subject: screen.inc extension
Date: Fri, 12 Apr 2002 14:38:35 +0200

http://news.povray.org/61ldbu8kmln7dlhdr539tohffoiobi2k4s%404ax.com
http://news.povray.org/9bldbu02kv1nairhk1v6v25v1pivhssnjs%404ax.com

ABX

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Let me make two things clear:
- I just want to move what makes a perspective camera different from a
spherical one.
- I fully understand 3D and stereo because I figured it out myself,
instead of looking at how others think it works. I mean it.

Jonathan

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Jonathan <nomail@nomail> wrote:
> - I fully understand 3D and stereo because I figured it out myself,

  I'm just being pedantic here, but I don't see how the latter proves
the former...
  Have you ever though you might actually be *wrong* sometimes? ;)

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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Warp <war### [at] tagpovrayorg> wrote:
> Jonathan <nomail@nomail> wrote:
> > - I fully understand 3D and stereo because I figured it out myself,
>
>   I'm just being pedantic here, but I don't see how the latter proves
> the former...
>   Have you ever though you might actually be *wrong* sometimes? ;)

1. What is a perspective camera?
2. How is it used properly?
3. How is it used properly in cross-eyed stereo?

I can try to visualize the problem.

Jonathan

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Hash: SHA1

Jonathan wrote:
| Let me make two things clear:
| - I just want to move what makes a perspective camera different from a
| spherical one.
	AFAIK there is no difference between the two. Or rather "perspective
camera" doesn't mean anything by itself: it is either "spherical
perspective camera", or "cylindrical perspective camera" but when
people say just "perspective" they usually mean "spherical
perspective"...

| - I fully understand 3D and stereo because I figured it out myself,
| instead of looking at how others think it works. I mean it.
	Then maybe you should explain to us how *you* think it works, so we
can understand your problem (In fact, actually putting it in simple
words so that us morons can understand might help you figure out the
answer to your question).

		Jerome
- --
******************************
*      Jerome M. Berger      *
* mailto:jbe### [at] ifrancecom *
*  http://jeberger.free.fr/  *
******************************
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=?ISO-8859-1?Q?=22J=E9r=F4me_M=2E_Berger=22?= <jbe### [at] ifrancecom> wrote:
> Jonathan wrote:
> | Let me make two things clear:
> | - I just want to move what makes a perspective camera different from a
> | spherical one.
>  AFAIK there is no difference between the two. Or rather "perspective
> camera" doesn't mean anything by itself: it is either "spherical
> perspective camera", or "cylindrical perspective camera" but when
> people say just "perspective" they usually mean "spherical
> perspective"...

I assume people who answer here know a perspective camera is
a perspective camera (but apparently some don't). Remember
that the keywords in pov are perspective and spherical (!).

> | - I fully understand 3D and stereo because I figured it out myself,
> | instead of looking at how others think it works. I mean it.
>  Then maybe you should explain to us how *you* think it works, so we
> can understand your problem (In fact, actually putting it in simple
> words so that us morons can understand might help you figure out the
> answer to your question).

Hopefully this will make it clear:
<http://home.filternet.nl/~eo000199/jonathan/povray/stereo.png>

The cylinders are perpendicular to both the 'real' and 'virtual' planes,
and end up at the 'reference point'. The rest is self-explanatory.

Note that this is almost 'perfect'. I was only too lazy to calculate
some minor rotations which would push it to the hard limit.

Jonathan

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