I agree with Paul Bourke, cameras should always be
parallel. Converging (what you refer to as cross-eyed
view) cameras introduce keystone distortion. Stereo
set ups based on converging cameras only work with
a short depth of field. Converging cameras do set the
stereo window at the convergence point, which is
convenient, but you can set the stereo window of
parallel views by trimming the excess.

Correctly rendered stereo pairs can be viewed by
the cross-eye method, but not created by toe-in of
the cameras.

"Wolfgang Wieser" <wwi### [at] gmxde> wrote in message
news:40670613@news.povray.org...
> Hi all,
>
> I want to set up a nice stereoscopic camera for anaglyphs, cross-eyed
> view and parallel view images. [Results will be made available publically
> when I succeed...]
>
> I know, there is StereoPOV but I need to look more precisely at the issue:
> IIRC, StereoPOV uses a non-perpendicular camera which results when
> simply doing:
>
> location = location +- eye_distance/2 * right;
> direction = direction -+ eye_distance/(2*stereo_win_distance) * right (*)
>
> (stereo_win_distance is the distance where the left and right rays
> cross each other and hence the plane which seems to be at the depth of
> the projection screen plane when viewed stereoscopically.)
>
> I do not understand why it is correct to use such a non-perpendicular
> camera.
>
> According to my understanding, the camera actually is generally NOT
> perpendicular but the angle between right and direction (=delta) depends
> not only on the ratio of eye_distance to stereo_win_distance but also on
> the actual eye ray crossing distance when viewing the image.
> This means that
> (a) cross-eyed view and parallel view require different delta-angles.
> (b) the above description (*) is incorrect; e.g. for anaglyphs one would
> need to compensate for eye ray crossing at the image "center" (focal
> point) depth rather than at the stereoscopic window depth.
> My experiments, however, did not yet confirm that.
>
> I hope anyone here has enough clue to point out exactly what is going on.
>
> Regards,
> Wolfgang

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