Sean Spicer (spicer@bme.stanford.edu)
Tue, 29 Feb 2000 09:40:31 -0800
I think I can explain why you're having dithering problems on your Octane
and O2.
The problem, I believe, lies in the fact that your machine does not have
enough frame-buffer memory to perform alpha-blending calculations to
specified accuracy given your screen resolution. Typically, you need at
least 8 alpha bits to properly generate an alpha image on any machine. An
Octane (SE, SSE, SI, SSI) does not have enough frame-buffer in 1280-1024
mode to provide 8 bits of alpha (Although MXE and MXI boards do). Here's
the fix: if you want properly rendered images on your Octane and O2,
simply setmon the machines down to 1024x780 screen resolution. Not an
elegant solution, but it gets the job done. (BTW, this is what we have
done with all our SGIs in the BME dept. here at Stanford -- just to get
proper rendering results!)
Hope that helps!
sean
On Tue, 29 Feb 2000, Mark Davey wrote:
> Hi...
>
> Ok.. I would like to thank everyone for responding to my previous e-mail
> concerning the problems I have been having with our new octane. I did
> initially think that the problem was due to me remotely logging on to an
> Onyx and running the Volumizer demos from there. However, I have
> discovered that ALL graphics on the Octane are dithered, not just those
> generated when remotely logging on to a different machine. Surely the
> Octane can produce 24 bit colour? We also have the same problem with the
> O2 machines here but up until now I havent given it much attention.
>
> I know that this question now is no longer directly relevant to
> Volumizer but does anyone have any ideas. The problem is not a
> client-server one and so VizServer is not the answer.
>
> Regards
> Mark
>
> --
> From: Mark Davey
> Dept. of Medical Physics, UCL.
>
> TEL: +44 (0)171 915 1673.
> FAX: +44 (0)171 837 9279.
>
> Institute of Laryngology and Otology,
> 330 Gray's Inn Road,
> London.
> WC1X 8GE.
>
>
>
--
___________________________________________________________________________
Sean Spicer Stanford University Medical Center
Biomechanical Engineering Division of Vascular Surgery, Suite H3642
Cardiovascular Biomechanics Lab Stanford CA, 94305
Telephone...650.723.1695
Fax.........650.723.8762
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