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Line2D intersection

From: David Gilbert
Subject: Line2D intersection
Date: Mon, 02 Aug 2004 15:23:43 +0100

Hello All,

I've recently started exploring Classpath to see where I can help out. 
In general, I am interested in Java2D, since the project I work on
(JFreeChart) depends on this quite a lot.  My FSF copyright assignment
is already completed.

To begin with, I've written some test cases for the Line2D class, and
sent these (just now) to the Mauve patches mailing list.  Another
developer (Sven de Marothy) previously posted a test case that
highlights a problem with the Line2D.linesIntersect() method.  I didn't
find any additional problems.  

I modified the Line2D class to correct the linesIntersect() method - a
patch is attached.  The fix is based on an algorithm described in
"Computational Geometry in C" (2nd edition) by Joseph O'Rourke.  I have
no background in computational geometry, by the way, just a mild
interest - so my code may be rubbish (but it passes the test cases,
which the existing code doesn't).

Re-reading Sven's earlier post, it sounds as though he has a fix for the
problem also, which I'll try to find out more about (I couldn't find it
posted anywhere).  Of course, if I had read his post properly the first
time, I would have found out about his fix before writing one myself...


Dave Gilbert

Attachment: Line2D-patch.txt
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