Thorsten said:
> But they are not wrong!  As soon as your eyes focus on something this is
> precisely the effect you have.  What you are trying to generate is an
image
> infinitely far away, so your eyes have to look nearly parallel.

That is true, our EYES see the images this way, but our brain does not.
I don't think he is trying to generate an image at infinity, but expects it
to look as if it were at infinity, because he (we) can't recreate the
viewing experience of looking at a scene close to our face. Also, it
is convergence that is the issue, not focus. The eyes cross (converge)
on close objects.

Our eyes begin to converge from parallel at about 2m (six feet), we
don't notice it until things are close, like 0.3m. Our perception
adjusts for geometric distortion and other issues when we focus
close and converge our eyes, for example we ignore the distant
background which is out of focus and can't be stereoscopically
fused (it is a "double image"). Minor keystone distortion is likewise
ignored. When we view a pair of images rendered from this geometry later
on the computer screen it is disturbing because we don't have the
ability to ignore or compensate for the distortions because we are
viewing it in a different context and with parallel eyes focused at a
different depth. That is why one should always generate stereo
pairs with parallel cameras. The issue becomes how to set the
"stereo window" which is the virtual frame created by the edge of
the image. I set the stereo window by trimming the left and right
edges of the stereo pairs.

> As you keep talking about viewport limits I suppose your problems
> understanding the correct behavior come from the use of z-buffer based
> algorithms.  It is indeed true that for those when rendering stereo views
the
> viewport is commonly moved, but this is only an approximation necessary to
> avoid having to transform the whole scene in order to keep the rendering
fast.
> The image you call "bad" is actually the correct image for a stereo view
of a
> human eye and the "good" one a simple approximation similar to those
commonly
> produced by a z-buffer based stereo renderer.

I know nothing of z-buffer based algorithms, but I would argue that the
image
Vic labeled as "good" was rendered correctly for stereo viewing, and the
"bad" image was rendered accurately for what the eye sees, but not for what
the brain perceives or for stereo viewing.

Harolddd

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