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Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!sharkey!itivax!dhw
From: dhw@itivax.iti.org (David H. West)
Newsgroups: comp.lang.c,comp.lang.lisp,comp.ai
Subject: Re: Need help with finding perimeters of bounded areas
Keywords: area, bounded, pos/neg images
Message-ID: <4188@itivax.iti.org>
Date: 13 Oct 89 14:20:12 GMT
References: <135@unicom.UUCP>
Reply-To: dhw@itivax.UUCP (David H. West)
Followup-To: comp.lang.c
Distribution: usa
Organization: Industrial Technology Institute
Lines: 16

In article <135@unicom.UUCP> miller@unicom.UUCP (Gregory S Miller) writes:
>Consider an area A on an euclidean plane surface.  Inside A 
>are an arbitrary number of lines that "fill out" A.  That is,
>A is defined not by a perimeter, but rather as a filled object (
>negative versus positive images...).

>Problem: Given the area A, find the perimeter - eliminate all lines
>	 inside A and leave just the outline.  A is "given" by a
>	 list of vectors with a diameter (ie. start/end point with
>	 diameter). 

I imagine one could simplify one of the perimeter-marching convex hull
algorithms fairly straightforwardly to do this. See e.g.
Preparata and Shamos, Computational Geometry, Springer, 1985.

-David West        dhw@itivax.iti.org