Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Tue, 1 Oct 1996 14:58:40 +0100
I find it slightly scary that you seem to get conventional zbuffer writes
with multisample(TRUE). Maybe I'm just being precious but what happens if
you have stencil operation & a different number of z & stencil bits between
msbuffer & framebuffer?
BTW, I like the concept of an average pixel depth, especially with
MStransparent objects :)
Angus.
On Oct 1, 9:33am, Bernard Leclerc wrote:
> Subject: Re: Final word on reading the Z-buffer in Performer 2.0
> On Sep 27, 2:38pm, Janet Estabridis wrote:
>
> > Some information:
> >
> > RE2, IRIX 5.3 --
> >
> > You can read the zbuffer successfully from Performer 2.0 in a draw
> > callback routine using glReadPixels. You can have texturing enabled and
> > multisampling visual enabled. I have now succeeded thanks to Jenny at
> > SGI. Things work like they are supposed to, I just swapped GL_FLOAT and
> > GL_DEPTH_COMPONENT in the glReadPixels and I never caught it until I
> sent
> > her my code.
> >
>
>
> Angus Dorbie replied:
>
> > This seems misleading, are you saying you managed to read the zbuffer
> > on RE2 while multisampling?
> >
> > Did you turn on pfAntialias or just have the visual without actually
> > using multisampling?
> >
> > Did you mean Infinite Reality?
> >
>
>
> We're using the RE2, IrisGL, IRIX 5.3 and Performer 2.0
>
> In order to read the depth component of a channel, we configured the frame
> buffer with
>
> RGBsize(12);
> zbsize(32);
> stensize(1);
> mssize(4, 32, 1);
> gconfig();
>
> This way, we have anti-aliasing available and the normal Z buffer is also
> active so we can read it to obtain the depth component with
>
> readsource(SRC_ZBUFFER);
> lrectread(x1, y1, x2, y2, parray);
>
> Of course, the Z components obtained correspond to the closest pixels
> written to the multisample buffer. It's not an average value - but it's
> better than nothing.
>
> As far as I know, there is no way to obtain the resulting depth component
> from the multi-sampled buffer. Only the normal Z buffer can be read.
>
> --
> Bernard Leclerc CAE Electronics Ltd., 8585 Cote De
Liesse
> Technical Leader Saint-Laurent, Quebec, Canada, H4L-4X4
> 3-D Graphics Applications tel: +1 514 341 2000 extension 2275
> bleclerc++at++cae.ca fax: +1 514 340 5496
>-- End of excerpt from Bernard Leclerc
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