Message-ID: <351AD81E.E9F2939C@wpol.com>
From: John & Sue Kissell <jdk AT wpol DOT com>
Reply-To: jdk AT wpol DOT com
MIME-Version: 1.0
Newsgroups: comp.os.msdos.djgpp
Subject: Re: point inside polygon detection
References: <6fce42$md4 AT bgtnsc02 DOT worldnet DOT att DOT net>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 26
Date: Thu, 26 Mar 1998 19:25:48 GMT
NNTP-Posting-Host: 208.195.214.68
NNTP-Posting-Date: Thu, 26 Mar 1998 14:25:48 EST
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

This may be total nonsense, but it seems to me that you should be able
to compare the point's coordinates to the *average* location (+ or - 1/2
the size in X and Y) of the object's corner coordinates. This is easy to
see with a plain (all right angle) rectangle, but without testing it
could be absolute rubbish for non-regular objects.


Hope this gives you some ideas,
John Kissell

Steve Patton wrote:
> 
> Hi,
> 
>   Is there a quick easy way to detect whether a point lies within the
> boundaries of a 2d polygon?  Right now I'm dealing with a four sided
> polygon.  This shape could be a rectangle (at any rotation angle, or
> distortion), trapazoid, etc, any 4 sided polygon.  This has to be checked a
> LOT, so I would appreciate an efficient algorithm.  Source code is not
> neccessary, if you can give me an idea, I can run with it.  Thanks!
> 
> --
> -Steve
> Personal : http://home.att.net/~pattonl
> Business : http://home.att.net/~pattonl/digital_resources.htm