Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!psuvax1!rutgers!cbmvax!cbmehq!cbmger!peterk
From: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Clicking on irregular shapes?
Message-ID: <1079@cbmger.UUCP>
Date: 8 Apr 91 08:10:55 GMT
References: <1991Apr05.104141.2118@cs.ruu.nl> <27867@neptune.inf.ethz.ch>
Reply-To: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Organization: Commodore Bueromaschinen GmbH, West Germany
Lines: 29

(Sorry, deleted the originator's name.)
> [an algorithm for determining whether a point's inside a polygon]
>
>I am currently writing a game that needs this (and probably will never be
>finished :^). Now what about this:
>        /\
>       /  \    /\
>      / O  \  /  \                                                   X
>     /      \/ ___\
>    /_______  /
>            \/

I always have moot feelings with such analytical algorithms. Often
you have to compare for equality of real numbers, which is normally
a NO-NO. You would have to convert coordinates to integers only to
do this algorithm on them.

Look for another example at this shape, would it be
processed correctly?
      /\
     /  \       /\
    / O  \_____/  \
   /_______________\

The O is thought to be on the same y coordinate as the horiz. line.

-- 
Best regards, Dr. Peter Kittel  // E-Mail to  \\  Only my personal opinions... 
Commodore Frankfurt, Germany  \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk