Re: distortion correction
Angus Dorbie (dorbie++at++multipass.asd.sgi.com)
Fri, 30 May 1997 15:51:41 -0700
On May 30, 1:03pm, Rémi Arnaud wrote:
> Subject: Re: distortion correction
> 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
Whoooaa, convert to .gif first :-)
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on Mon Aug 10 1998 - 17:55:20 PDT