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From: andreess@mrlaxs.mrl.uiuc.edu (Marc Andreessen)
Newsgroups: comp.sys.sgi
Subject: Re: VGX vs. PI Shading: Dithering
Message-ID: <1991May30.222521.18295@ux1.cso.uiuc.edu>
Date: 30 May 91 22:25:21 GMT
References: <9105232209.AA01931@snowhite.cis.uoguelph.ca>
Sender: usenet@ux1.cso.uiuc.edu (News)
Organization: University of Illinois, Urbana
Lines: 18

In article <9105232209.AA01931@snowhite.cis.uoguelph.ca> devans@SNOWHITE.CIS.UOGUELPH.CA writes:
>  It just hit me that the cause was the fact that PIs have only 24
>bitplanes.  So, when I used double buffering, I really got 12 planes
>per buffer.  Then the pipeline dithered to make the colours look OK.
>I have no idea how many planes the VGX has (I'd be interrested in
>knowning, though...), but I'm sure it would have 48....so it could
>do full 24-bit double-buffering.  That would explain the "soft" vs.
>"hard" look
>  This seems too simple...am I right in my assumption?

Yup... this is true on IBM RS/6000 24-bit boards also (12 bits/buffer 
with dithering).

Marc

-- 
Marc Andreessen___________University of Illinois Materials Research Laboratory
Internet: andreessen@uimrl7.mrl.uiuc.edu____________Bitnet: andreessen@uiucmrl