From: psantangeli@alias.com (Peter Santangeli)
Subject: Re: TECH: Re: New 386 polyblit release
Date: 	Wed, 5 Feb 1992 10:18:32 -0500
Organization: Alias Research, Inc. Toronto Canada



In article <1992Jan29.221159.2416@watserv1.waterloo.edu>, broehl@watserv1.
waterloo.edu (Bernie Roehl) writes:

> In article <1992Jan28.152614.27104@swvgs.vak12ed.edu> govstude@swvgs.
> vak12ed.edu (Southwest Virginia Governor's School STUDENT) writes:
>
> A blitter is any piece of software or hardware that does very fast screen
> writes.  The name derives from the "blt" or "block transfer" instructions
> on certain cpu's that move blocks of data around in memory very quickly.

I'm sorry, but I have been holding my tongue on this one for too long.

A. A blitter is in fact a piece of hard/software for moving rectangular
   blocks of data around or on/off a frame bufffer. The common usage 
   for such a thing is to move windows etc. around a screen (but much 
   more interesting things can be done them).

B. A piece of of hard/software that displays polygons in a frame buffer
   IS NOT A BLITTER. It is a POLYGON SCAN CONVERTER. It is named such
   because its purpose is to take the cartesian definition of a polygon
   and convert it into spans of pixels for each of the scan lines
   covered by the polygon. 

Please excuse my ranting about mere terminology, but this is a very
fundamental point, and let's face it, VR is currently suffering badly
from a lack of formalism.

I would suggest to those who want a better background in this kind
of thing to read "Fundamentals of interactive computer graphics"
by Foley and Van Dam, or "Computer Graphics principles and practice",
by Foley, Van Dam, Feiner, and Hughes.

Those wanting to really make graphics sing should read "Graphics Gems"
edited by Andrew S. Glassner, and "Graphics Gems II", edited by
James Arvo

-- 
Peter Santangeli                              -- 
Graphics Software Designer                   /          Alias
Strategic Research                          /   \       Research
psantan@alias.com                          /     \_     Inc.