Mario Veraart (rioj7++at++fel.tno.nl)
Fri, 27 Mar 1998 18:57:09 +0100 (MET)
>
> Hi pfAll:
>
> I am using Performer 2.2 on an Onyx i-station with IRIX 6.2. I want to
> read the z-buffer values for my currently displayed frame, and save them
> as an image file (ppm format), for image processing purposes. But I am
> having some troubles with it. To save such an image I modified the file
> perfly.C.
>
> [snap]
>
>
> glReadPixels(...,GL_RGBA,...) works fine.
>
> The GL_DEPTH tests show the following results:
>
> frame_snapshot: bias 0.000000, scale 1.000000, bits 23.000000, range
> (0.000000, 1.000000), depth testing enabled
>
> In my opinion, this means glReadPixels(...,GL_DEPTH_COMPONENT,...)
> should work. But I get for every pixel the value z=1.0 !!
>
>
> Any idea why glReadPixels(...,GL_DEPTH_COMPONENT,...) douesn't work in
> my application?
If you have antialiasing enabled then you might have problem reading
the Z-buffer, because then you have for every sub pixel a possible
Z-value.
Mario
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