Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!mailrus!tut.cis.ohio-state.edu!bloom-beacon!oberon!pollux.usc.edu!papa
From: papa@pollux.usc.edu (Marco Papa)
Newsgroups: comp.sys.amiga.tech
Subject: Re: 32 shades of gray
Keywords: gray scale
Message-ID: <7510@oberon.USC.EDU>
Date: 9 Mar 88 02:18:37 GMT
References: <2801@gryphon.CTS.COM> <7941@tut.cis.ohio-state.edu>
Sender: news@oberon.USC.EDU
Reply-To: papa@pollux.usc.edu (Marco Papa)
Organization: Felsina Software, Los Angeles, CA
Lines: 22

In article <7941@tut.cis.ohio-state.edu> mills-cl@pike.cis.ohio-state.edu (christopher mills) writes:
>In article <2801@gryphon.CTS.COM> richard@gryphon.CTS.COM (Richard Sexton) writes:
>>Alright, I'm letting you guys in on one of my secrets.
>>I've been using this tip to acheive what looks for all the world
>>like 32 gray scales.
>	Not so big of a secret.  My first ray-tracing attempts were in black
>and white, 640 x 400, 16 shades of grey with a 2 x 2 dither patern, giving
>(as I recall) 61 shades of grey.  It looked pretty good...

Come on, guys! This stuff has been in the literature for over 6 years.   Take
a look at "Fundamentals of Interactive Computer Graphics" by J.D. Foley and 
Andrew Van Dam, published in 1981:

"Halftone approximation", on page 597-602 on bi-level displays [1 bit/pixel],
and "Reporoducing Color Hard Copy", p. 620, on generating 125 different colors
on 3 bit/pixel displays. This is how it is done on Tektronix 4105/4107 
terminals (see Color Plate  27).  I did it on the Amiga for our unreleased
Tek 4105 emulator, and it looked pretty good, except for the flicker. Nothing
new.  Just what everybody should now by now.

-- Marco