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Path: utzoo!linus!philabs!cmcl2!seismo!utah-cs!arizona!rogerh
From: rogerh@arizona.UUCP (Roger Hayes)
Newsgroups: net.graphics
Subject: Dithering and a project
Message-ID: <16648@arizona.UUCP>
Date: Wed, 17-Oct-84 23:59:42 EDT
Article-I.D.: arizona.16648
Posted: Wed Oct 17 23:59:42 1984
Date-Received: Fri, 19-Oct-84 01:52:19 EDT
References: <1556@ucla-cs.ARPA>
Organization: Dept of CS, U of Arizona, Tucson
Lines: 21

On the 24-to-8 issue: dithering is quite simple and produces good
results.  The technique can be derived starting from the 2 pages in
Foley and Van Dam.  I usually dither to 3-3-2 bits (rgb) when I have an
8-bit frame buffer -- does anyone take the trouble to divide the target
color space evenly?

On another issue -- I need a pointer to literature on incremental (ie,
generalized Bresenham) techniques for drawing quadratic curves.  I have 
a raycaster working (arbitrary quadric shapes, boolean combinations), but
it's deathly slow.  To speed it up, I would like to use the information 
from one ray to determine the next; I need a quick way to determine the 
solution for z of
	A*z^2 + B*z*x + C*z + D*x^2 + E*x + F >= 0
at (x+1), given the solution at x.  "Quick" means faster than substituting
the new x value and solving directly.

	Roger Hayes
	University of Arizona
	rogerh%Arizona@csnet-relay.CSNET
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