Michael M. Allbright (m-allbright1++at++ti.com)
Fri, 31 Jan 1997 18:44:46 -0800
I took your advice and took a look at the Rapier demo on the Octane, however
there was really no anti-aliasing evident. Perhaps you have seen a different
version? I tried the "w" key to turn on wireframe mode, and the aliasing was
even more evident.
If you can point me to the version you have seen, it would be very helpful as I
must convince management of the efficacy of wireframe anti-aliasing before I
can purchase new equipment.
Thanks again,
--Mike
------------------
Original text
From: "Angus Dorbie" <dorbie++at++bitch.reading.sgi.com>, on 1/31/97 7:27 PM:
OCTANE can anti-alias in Real Time, read on.
Get your sales Rep to show you an OCTANE or Indigo2 IMPACT
running the "RAPIER" demo. It anti-aliases the targets using a
second pass with textured, lit wireframe.
In general anti-aliasing isn't that big a problem for IMPACT for
several reasons:
1) trilinear MIP mapping and point sampled polygon edges mean you
only need it where texture ID changes or you get a shilouette.
2) You can use a wireline pass very effectively to get high quality
blended edges in a scene and can control the load. The fill performance
hit is manageable because it's wireline.
3) Soft edge blending alpha textures like tree lines mean you you never
need it for blended alpha textures.
You may also want to look at ONYX2 Reality, if you must have
multisample at IMPACT fill performance but not at 4x cost.
Accumulation buffering is expensive, it's multipass + accumulation
operations.
Lets say you want 4 samples, you have to draw _everything_ four times,
geometry and pixel fill, accumulate four images and copy to framebuffer
once, simulation death.
And that's just for four samples. If you perform the line anti-aliasing
mentioned above you get the edge quality equivalent of 256 samples.
Thet're not weighted as accurately as multisample but it's a _big_
improvement over no AA in any simulation.
Cheers,
Angus.
On Jan 31, 11:58am, Michael M. Allbright wrote:
> Subject: Non-MultiSample Anti-aliasing
> Howdy:
>
> I am considering the purchase of an Octane or two, but I am very concerned
> about aliasing. I understand that the Octane does anti-aliasing of points
and
> lines only--no polygon anti-aliasing. Since the next OpenGL machine capable
of
> hardware polygon antialiasing seems to be an Onyx IR at about 4 times the
> price, I am seriously considering antialiasing using the accumulation buffer
> (although I have yet to verify that the accum. buffer will be available on
the
> Octane in the rendering mode our simulator uses).
>
> Hence the question:
> Can anyone share any hints/tips/tricks/gotchas/code-snippets/algorithms or
just
> plain old advice on the subject of anti-aliasing using the accumulation
buffer,
> or similar techniques on Max Impact/Octane level machines?
>
> Thanks
> --Mike
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>-- End of excerpt from Michael M. Allbright
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