Re: off-axis projection for stereo

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Mario Veraart (veraart++at++fel.tno.nl)
Thu, 25 Feb 1999 14:31:32 +0100

Liu Xiaoyan wrote:
>
> Hi, all,
>
> I just learned that calling glTranslate or
> glRotate onto GL_PROJECTION matrix will
> mess up opengl rendering. However, for proper
> stereo effect, 2 channels doing off-axis
> projection are required.
To my knowledge that is not true.
You need 2 channels that have different viewing directions but
who are on-axis projections. And that is where the setViewOffset
comes in place. It just specifies what extra transformation
are to be applied for this channel after the setView transformation
is done.

Of axis projections are needed if you have to combine multiple channels
to create a kind of videowall. They all compute part of the larger
picture.
All channels use the same projection plane but it is not perpendicular
to the viewdirection for all channels.

Mario
>
> Just wonder what does the following paragraph from
> pfChannel manpage mean exactly:
>
> >Both translation and rotational offsets are
> encoded in the graphics
> >library's ModelView matrix. This ensures
> that fogging is consistent
> >across multiple, adjacent pfChannels.
>
> Does the "offsets" include both transformations
> from channel->setView and channel->setViewOffset?
> I guess it should include both.
>
> Thanks for help.
>
> Liu

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