On Thu, 14 Jun 2001 12:42:59 -0400 Bill DeWitt wrote:

>
>    Is there a way to render stereo versions of an image in one pass? Other
>than setting up some mirrors?
>
>    I want to do an animation in stereo and I don't want to paste together
>all those images...
>

  Hi, Bill. See Glenn McCarter's "Dawn Patrol" image and text description. I
think this will do what you want.

http://www.irtc.org/stills/1998-02-28.html

-- 
Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer

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Well damn, why didn't we hear about this!!
Great. Thanks for letting us know. I'd very
much like to have a copy of the program.
Any chance it could be added to MegaPOV or
POV 3.5??

Harold

"Benk" <Ste### [at] ruhr-uni-bochumde> wrote in message
news:3b299dc5$1@news.povray.org...
> Why don't any one know this link?
>
> http://sabix.etdv.ruhr-uni-bochum.de/sabpov/
>
> If you want to render Stereo images, let me know it.
>
> Let me also know, if ther is anyone of the theoretical stereo
> camera macros is working well.
>
> Stefan
>
>
>

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>>
>>  |    |
>>  |    |
>>  \-\/-/
>>    ||
>>    __
>
>
>    When I do that, I get a single image in the center, which
>experimentation reveals is both halves joined in the middle.

Ok, time for some physics...; let's just consider the right-hand image.

The ray that corresponds to the left side of the camera leaves in the +y
direction.  It reflects off the first mirror, and is now travelling <1,0>
It reflects from the second mirror, and is now travelling <0,1>.

I.e The left-hand edge of the right-hand image is the view dead ahead.

For a stereo image, if your angle of view is theta degrees, then you want
the left side of the right hand image to correspond to <0,1> rotated by
<- theta/2 degrees>.

Now consider the right side of the image.  With your mirror arrangement,
the ray leaves the camera at <sin(theta/2), cos(theta/2)>.  After the double
reflection, it'll leave the second mirror at that same angle.  So this ends
up at the right angle, although there is a bit of distortion introduced by
the fact that the right edge of the mirror is further away than the left edge.

What you want to have happen is that the mirror combo should reflect the
left-hand edge of the right-hand image to an angle of <-sin(theta/2), 
cos(theta/2)>; the right hand edge of the image to an angle of <+sin(th/2),
cos(th/2)>;  This is equivalent to the center of the right hand image 
looking dead ahead.

I.e. camera angle <+sin (theta/4), cos(theta/4)> gets reflected to <0,1>

Actually doing the math is fairly simple, but I don't happen to know what
the field of view for a standard camera is, so I can't run the numbers 
for you.

As a side note, If you use an arrangement more like:

    |
    |
/   |
||  |
| | |
|  ||
e   /

You'll have less distortion, because the difference in beam-length to the
different sides of the mirror will be less (although the total beam-length
will be longer)

Jamie

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"James Tonkin" <jrt### [at] calumcsclubuwaterlooca> wrote :
>
> Actually doing the math is fairly simple, but I don't happen to know what
> the field of view for a standard camera is, so I can't run the numbers
> for you.

    Actually just setting up the mirrors has been fairly simple. Making them
move with the camera as it pans and sweeps while keeping the mirrors pointed
at the look_at point is the hard part...

    There seems to be another problem with the point or perspective camera.
My drawing (in PBI) shows what I think is happening. I think I will end up
wanting a curved mirror or a different camera.

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in news:3b2a50bf$1@news.povray.org Bill DeWitt wrote:

>     Actually just setting up the mirrors has been fairly simple.

Havn't followed this thread, but maybe this helps:
http://www.irtc.org/stills/1998-02-28.html
The third-place picture is done using mirrors

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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Bill DeWitt wrote:
> 
> Is there a way to render stereo versions of an image in one pass?
> Other than setting up some mirrors?
> 
> I want to do an animation in stereo and I don't want to paste together
> all those images...

Use POV-Ray to paste them together.  Paint one half of a plane with
one image, the other half with the other.  Use the str(,,) function to
select the file to use for each side, and then render as an animation.
Don't anti-alias the paste-up render.

I used a similar process to do the blocky digital censoring in my IRTC
entry titled "Showbots."

Regards,
John
-- 
ICQ: 46085459

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"ingo" <ing### [at] homenl> wrote in message
news:Xns### [at] povrayorg...
> in news:3b2a50bf$1@news.povray.org Bill DeWitt wrote:
>
> >     Actually just setting up the mirrors has been fairly simple.
>
> Havn't followed this thread, but maybe this helps:
> http://www.irtc.org/stills/1998-02-28.html
> The third-place picture is done using mirrors

    Thanks, but I am working on something a little beyond just a static
image. I am going through the vector sample files hoping that it will sink
in this time.

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Bill DeWitt wrote:

>    Actually just setting up the mirrors has been fairly simple. Making them
>move with the camera as it pans and sweeps while keeping the mirrors pointed
>at the look_at point is the hard part...

        When I want an object to move with the camera, I don't use
the look_at command.  Instead, I locate the camera at the origin <0, 0, 0>
Set the direction vector to <0, 0, 1> and then use rotations and
translation to point the camera.  I then use the same rotations and
translations on the object(s) that move with the camera.  Warning:
attempting to use a transform on a camera generates odd error
messages, so instead write a transform macro and call it from both
the camera and the object that is to move with the camera.

 #macro camera_trans()
   rotate x*7 // or whatever
   rotate y*18
   translate <0, 1, -10>
 #end

 camera {
   location 0
   direction <0, 1, 1>
   right <(640 / 480), 0, 0>
   up <0, 1, 0>
   camera_trans()
 }

 object {
   whatever
   no_shadow  // kind of handy
   translate <0, 0, 1> // so it is a little in front of the camera
   camera_trans()
 }


Pete

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"Pete" <Pet### [at] nymaliasnet> wrote in message
news:111### [at] nymaliasnet...
> Bill DeWitt wrote:
>
> >    Actually just setting up the mirrors has been fairly simple. Making
them
> >move with the camera as it pans and sweeps while keeping the mirrors
pointed
> >at the look_at point is the hard part...
>
>         When I want an object to move with the camera, I don't use
> the look_at command.

    Right, but I have to tilt the mirrors to converge on the look_at point.
If it is further away or closer, the mirror has to angle differently.

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Mirrors are slow to use if you want animation within a reasonable time (boy,
that varies person to person).
I too had made a stereo camera using the angled mirrors way, just a little
angle trickery involved.  No, nothing mathematical from me.  I found how the
subject of the view is next to impossible to get a good normal scene into
the camera.
I'm rushing through these news messages because my access was gone more than
3 days and it's catching up time so sorry if I rehash this point.
Seems Bill has come to the same conclusion.
If I remember right it was faster to render two times rather than a single
4-mirror way, for a simple scene anyhow.
That SAB POV looked great to me.  When will it be incorporated into
"official" POV-Ray? :-)
Thanks for that posting Stefan, expect e-mail as soon as I figure out where
the address is.

Bob H.

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