Newsgroups: comp.graphics
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From: butch@fergvax.unl.edu (FERGVAX Daily Operator)
Subject: Help with Painter's algorithm for non-intersecting polygons
Message-ID: <butch.677950472@fergvax>
Summary: Need Help
Keywords: painter's, sorting, polygon, drawing
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Organization: University of Nebraska - Lincoln
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Date: 26 Jun 91 15:34:32 GMT
Lines: 18

	I'm working on a polygon-based 3D graphing application and I need a good
sorting algorithm for the faces.  I've worked with just sorting on a Z value
(which I know doesn't work, but was enough to show my off the program at the
time) and I've looked in Foley-Van Damm at the Newell-Newell-Sanchez
algorithm.  The latter I like and it's precisely what I'm looking for.
However, I'm stuck:

	So, I've got some questions:  (1) How can you tell if one polygon is
completely on a one side of another polygon, and (2) There are cases where
adding a test for (1) does not completely insure a correctly sorted face list,
so could anyone recommend some extra criteria for correctly sorting
non-intersecting polygons?

Please e-mail me at butch@fergvax.unl.edu if you can help me.

Thanks in advance,

Butch