Re: distortion correction
Rémi Arnaud (remi++at++remi.asd.sgi.com)
Fri, 30 May 1997 13:03:05 -0700 (PDT)
Shawn Soeder wrote:
>
> Performers,
>
> I'd like to do distortion correction for three channels projected onto a
> spherical dome using an single- (soon to be multi-) pipe IR machine. Can
> anyone direct me to any info on the subject?
>
> If there are no references, is the following roughly in the right direction?
>
> 1) Make two pfScenes, one with the geometry I want to render and one with the
> geometry for the correction.
No, you make a distortion geoset, and draw it directly after pfDraw
> 2) Render the first pfScene into three channels that cover the required area.
Why 3 channels, maybe you need more, maybe you need less. You'd like
to optimize the texture readback, so you'd like 2 or 4 to cover a
rectangular area.
You may need more channels to avoid oversampling problems. Limit aperture
to 120 degres maximum on a channel.
> 3) After the pfDraw, copy the framebuffer to texture memory using
> pfSubloadTex.
Yes, turn off MIPMAP on that texture.
> 4) Reconfigure the channels to their proper size/orientation for the second
> pass.
Just set a non perspecive matrix, clean the color if necessary, turn off
Z buffer, set 2D drawing mode in fact
> 5) Render the second pfScene into the three channels, projecting the
> downloaded texture onto the new geometry.
Just draw the geoset(s)
> 6) Send the output to the projectors in the dome.
You can send the result to a texture, and apply that texture to
an object in the scene and redraw the whole scene. This how you
do reflective mapping (to answer another info-performer question!)
> 7) Look at the results, smile and experience quiet satisfaction.
Take a snap-shot and send it to info-performer
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on Mon Aug 10 1998 - 17:55:20 PDT