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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: net.graphics
Subject: Re: Y positive up or down?
Message-ID: <5298@brl-smoke.ARPA>
Date: Sat, 8-Nov-86 03:03:55 EST
Article-I.D.: brl-smok.5298
Posted: Sat Nov  8 03:03:55 1986
Date-Received: Sun, 9-Nov-86 03:37:48 EST
References: <478@vaxb.calgary.UUCP> <5139@brl-smoke.ARPA> <7291@utzoo.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 17

In article <7291@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>To quote from "Hardware/Software Trade-offs for Bitmap Graphics
>on the Blit", Pike/Locanthi/Reiser, Software-Practice&Experience Feb 1985:
>
>" ... All bitmaps share a single
>coordinate space, with (0,0) in the upper left. ... "

Ah, but in the ACM TOG, Apr 1983 Rob used 1st-quadrant.  It is worth
noting that almost all the algorithms are independent of this convention.
(Exercise:  Find the one that isn't.)

Note that I'm not arguing which is BETTER, since I've already pointed out
that that should be decided on the basis of observable consequences at
the user interface.  In my corner of the world, text-oriented stuff
should appear from left-to-right, top-down.  This argues fairly strongly
for at least STORING raster information in that order, but it has
somewhat less impact on the design of raster software/hardware internals.