Re: Quickdraw Regions Explained

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From: info-mac@uw-beaver
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Subject: Re: Quickdraw Regions Explained
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Date: Fri, 1-Feb-85 07:06:05 EST
Article-I.D.: uw-beave.709
Posted: Fri Feb 1 07:06:05 1985
Date-Received: Sat, 2-Feb-85 11:57:34 EST
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Organization: U of Washington Computer Science
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From: Bob Cralle

Why not encode a circle using Minsky's algorithm?k

x(n+1) = x(n) - k y(n)
y(n+1) = y(n) + k x(n+1) [x(n+1) is intentional, else spiral]

k is small const. Negative power of 2 is nice. x(0) = radius (y(0) = 0).
This scheme makes best circle (actually it's an ellipse). I found that it also
makes nice ellipses if 1st k = ke & 2nd k = k/e, where e is the eccentricity.

Pretty compact encoding: center of circle & small const.

Regards, Bob

p.s. I wrote a couple of short notes on this subject.
If interested I will send.