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From: ali@rocky.UUCP
Newsgroups: comp.graphics
Subject: Re: PC2 Graphics beats Amiga
Message-ID: <326@rocky.STANFORD.EDU>
Date: Sat, 23-May-87 12:49:36 EDT
Article-I.D.: rocky.326
Posted: Sat May 23 12:49:36 1987
Date-Received: Sat, 30-May-87 01:21:08 EDT
References: <522@titan.camcon.co.uk> <80002@wsucshp.UUCP>
Reply-To: ali@rocky.UUCP (Ali Ozer)
Distribution: world
Organization: Stanford University Computer Science Department
Lines: 34

In article <80002@wsucshp.UUCP> Mike Kibler writes:
>Besides resolution is only half the story. I am interested in
>bit planes.

Considering the hardware to push many bit planes around in real time
is still pretty expensive, I think Amiga's method of providing 4096 colors
at once without the use of 12 bit planes is pretty clever. (This is
known as the "Hold-and-Modify" (HAM) mode, it was described in detail a
while back on this newsgroup.) The current Amigas have 32 color registers, and
can display 32 colors in lo res (upto 352x474) or 16 in hi (upto 704x474). 
This combination of resolution/colors is fine for text applications, 
cartoon-like animation, business graphics, or genlock applications
(where you merge video signals with titles or other images and record on VCR),
but, as I've found out, if you really want to digitize an object and have
it look right you need more colors. (Dithering helps, but only to a certain
degree...) That's where the Amiga's HAM mode comes in real handy --- Images
digitized in this mode look exceptionally real. It requires some extra 
computation (< 30 seconds with the "Digi-View" digitizer I have) to compute
(not display, displaying is fast) a 12-bit image to look well in HAM mode,
but, the results are worth it and are usually indistinguishable from real (ie,
12-bit plane) images. Only images with many sharp edges of many different 
colors won't come out right, due to the HAM tradeoffs. (You'll get "fuzzy"
edges because of the fringing effects.)

Anyway, the point is that I like the idea of more bit planes, but I also love
the idea of being able to play with 4096-color images on a $1k machine.
I've been experimenting with "animation" in HAM mode (mostly by flipping
through compressed digitized images), and it is easily possible. (And 
"juggler" also is a good example of this, although the images are ray-traced
rather than digitized.) What would be the cost of a Mac II or IBM system 
which allowed you to do >10 frame/second 4096-color animation?  (Juggler
runs faster than 20 frames/sec.)

Ali Ozer, ali@score.stanford.edu, ...decwrl!rocky.stanford.edu!ali