decomposing an intersecting polygon?
tarka at SPAMLESS-zip.com.au
tarka at SPAMLESS-zip.com.au
Fri Sep 24 22:28:54 EDT 1999
Joe Strout <joe at strout.net> writes:
> I'm looking for an algorithm to decompose a self-intersecting 2D
> polygon into a set of non-intersecting polygons, according to the
> "odd-even" winding rule. That is, if the polygon defines a
> five-pointed star by five lines, the center of the star should not be
> filled.
>
> The purpose is to implement this odd-even filling on systems that have
> no native support for it, for a cross-platform drawing library in
> Python.
If it's purely filling that you're interested in then XFree86 has some
fairly optimal filling routines implementing both the odd-even and
winding-number rules. These could be translated into Python without
too much pain.
The routines are buried quite deep in the XFree86 sources, but I have
some trimmed down C++ versions of them which I could mail to you.
Cheers,
Steve
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