Re: Polygon Question...

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#497

From: Larry Jones
Date: Sat, 25 Jul 1992 22:37

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In article <1992Jul21.221038.7051@javelin.sim.es.com>, gclapp@javelin.sim.es.com (Glenn Clapp) writes:
> Traverse the polygon, calculating 3 cross products (v1->v2 X v2->v3,
> v2->v3 X v3->v1), and (v3->v1 X v1->v2), and if the cross products are
> positive, the polygon is counterclockwise, otherwise they will be negetive.
> Also, if you have a sign flip between the different cross products, then
> the polygon is not convex.

One is sufficient - a triangle is always convex.
----
Larry Jones, SDRC, 2000 Eastman Dr., Milford, OH  45150-2789  513-576-2070
Domain: lawrence.jones@sdrc.com               IBMMAIL: USSDR7DR at IBMMAIL
I thought my life would seem more interesting with a musical
score and a laugh track. -- Calvin

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Path: arc1-ca.pugleaf.net!sparky!uunet!sdrc!thor!scjones
From: scjones@thor.sdrc.com (Larry Jones)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Polygon Question...
Message-ID: <1886@sdrc.COM>
Date: 25 Jul 92 22:37:19 GMT
References: <1992Jul21.094844.1@camins.camosun.bc.ca> <1992Jul21.221038.7051@javelin.sim.es.com>
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