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From: goudal@geocub.greco-prog.fr (Frederic Goudal )
Newsgroups: comp.graphics,sci.math,comp.sources.wanted
Subject: Re: A deficiency in the Mac ellipse algorithm?
Message-ID: <1053@geocub.greco-prog.fr>
Date: 7 Mar 89 07:42:11 GMT
References: <395@brunix.UUCP> <4070@ingr.com> <339@gtss.gatech.edu> <7929@boring.cwi.nl>
Reply-To: goudal@geocub.greco-prog.fr (Frederic Goudal (achille))
Organization: Greco-Programmation, Bordeaux, France.
Lines: 25

In article <7929@boring.cwi.nl> jurjen@cwi.nl (Jurjen N.E. Bos) writes:
>I just found out that the "deficiency" in the Mac ellipse algorithm really
>is a feature: Drawing ellipses inside each other will have a nice look.
>This means that ellipses need to have holes to fit inside each other.

If you mean that drawing ellipses to fill an area don't give the expected
results (because of the holes), you don't have to worry about that, it's
simply at the present time impossible. But, you can fill an area with ellipses
with this algorithm : for each point of the area, you compute with elipse it
belongs. I don't know the exact algorithm.
You will have th same problem with lines, circles, and in general all curves :
just try to fill an area with parallels lines, depending on the direction, you
will find more or less holes, it's inherent to Bresenham algorithm.

So I hope that I have well understood what you mean.


a ciao.
babbs.

Claim : "I do apologize for my bad english"
-- 

goudal@geocub.UUCP          "Why can't we rich the sun?"
oral-maill : babbs		Pink Floyd