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Subject: Re: [boost] [geometry] robustness approaches
From: Simonson, Lucanus J (lucanus.j.simonson_at_[hidden])
Date: 2009-03-13 19:42:49

Barend Gehrels wrote:
> You'll probably found this on the mails and not on the library
> itself. It has no circles so it is a bit unfair to compare the
> approaches like this. It focusses on integer arithmetic and 45/90
> angled polygons so it is different, more or less complimentary.
I'm a little hurt to hear you say this. I keep repeating that I
currently handle arbitrary angle polgon set boolean operations and
that the implementation is 100% robust for integer coordinates but
not so for floating point. There are practically no robustness
issues with 90 polygons and only very little with 45 polygons, so why
would I discuss it if I didn't need to concern myself with it? When
I talk about robustness I'm talking about my arbitrary angle polygon
clipping implementation.
Allow me to demonstrate this capability more clearly. I have just
exercised my arbitrary angle polygons booleans with floating point
coordinates. It worked and successfully XOR-ed a hand
with a spiral which is a visually appealing but trivially small test
case of mine. I can't claim that it is 100% robust for floating
point coordinates (yet) but I do have working code.
I have attached both sets of outputs the image of the result as well.
It is clearly correct. Just because I
don't claim floating point robustness doesn't mean the algorithm
doesn't work or can't produce correct results. I just
haven't designed in and verified 100% robustness for floating point.



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