Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!bloom-beacon!athena.mit.edu!tuna
From: tuna@athena.mit.edu (Kirk 'UhOh' Johnson)
Newsgroups: comp.graphics
Subject: Re: Intersection between a line and a polygon (UNDECIDABLE??)
Summary: no, no, No, No, NO, NO
Message-ID: <14759@bloom-beacon.MIT.EDU>
Date: 29 Sep 89 03:59:56 GMT
References: <2972@ndsuvax.UUCP> <32610@cornell.UUCP>
Sender: news@bloom-beacon.MIT.EDU
Reply-To: tuna@athena.mit.edu (Kirk 'UhOh' Johnson)
Organization: Massachusetts Institute of Technology
Lines: 27

In article <32610@cornell.UUCP> deb@charisma.graphics.cornell.edu writes:
% In article <2972@ndsuvax.UUCP> ncsmith@ndsuvax.UUCP writes:
% >
% >  I need to find a formula/algorithm to determine if a line intersects
% >  a polygon.  I would perfer a method that would do this in as litte
% >  time as possible.  I need this for use in a forward raytracing
% >  program.
%
% I think that this is a very difficult problem. To start with,
% lines and polygons are semi-algebraic sets which both contain
% uncountable number of points. Here are a few off-the-cuff
% ideas.
%
% [ .... egregious volumes of hairy sounding stuff deleted .... ]

look in any respectable introductory graphics book (foley and van dam,
newman and sproull, etc.) and you'll see that this is a solved (many
times over) problem.

it is definitely _FAR_ from undecidable; it's actually fairly simple
to solve.

if after you've found such a book and read what it has to say you find
yourself still completely confused, then try asking the net for
guidance.

kirk