Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!cornell!batcomputer!eric
From: eric@batcomputer.tn.cornell.edu (Eric Fielding)
Newsgroups: comp.sys.mac
Subject: 24-bit Video
Message-ID: <3634@batcomputer.tn.cornell.edu>
Date: 5 Feb 88 22:33:20 GMT
Reply-To: fielding@geology.tn.cornell.edu
Organization: Department of Geological Sciences, Cornell University
Lines: 31

In a recent article olson@endor.UUCP (Eric K. Olson) wrote:
>In early Mac II documentation, there are references to 16 and 32 bit modes.
>It's a pity these were eliminated, since the 24-bit cards now becoming
>available have a painful programming interface...
>Then again, a full 16-bit color lookup table would be about 524K.  A 32-bit
>one would be about 34 Gigabytes-- perhaps these resolutions were never
>intended to be used with color-lookup tables.
>The same document referred to 1-1-1, 2-2-2, 4-4-4, and 8-8-8 chunky-planar
>pixel organizations (the 8-8-8 would have been perfect for the OpCode or
>SuperMac 24-bit cards).
>Eric K. Olson     olson@endor.harvard.edu     harvard!endor!olson     D0760

I asked the net a little while ago how the new 24-bit cards are working now,
and all of the responses were that they looked good, but were slow.  Someone
(I don't have it handy) said that the cards have special graphics processors
that are not yet being used by the software (I assume to draw lines, etc.).

My experience is with special-purpose image processors that organize the
video memory into 8-bit planes, and then have three separate LUT's one each
for the red, green, and blue guns.  As Eric O. points out, it is very expensive
to have one giant 24-bit LUT, but for anything I am interested in, the
3 8-bit (actually I think ours are 12-bits internally) work perfectly. It
sounds like this is exactly what some manufacturers have done for their
cards.  It is a severe disadvantage if the QuickDraw routines do not 
support some kind of R-G-B "chunky" pixel organizations.

Maybe the special purpose image processors will be around for a while longer.

++Eric Fielding

eric@tcgould.tn.cornell.edu   cornell!batcomputer!eric