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Subject: [ggl] incorrect result for an intersection
From: Simonson, Lucanus J (lucanus.j.simonson)
Date: 2011-04-17 16:51:18

Arash Partow wrote:
> Simonson, Lucanus J wrote:
>> Is that so? What is something more reasonable? I'm not a big
>> believer in the idea of templating the number type of a non-robust
>> computational geometry algorithm and substituting infinite precision
>> or lazy exact data types. I know it can be done, I'm just not
>> impressed with the results. Does the license they use allow such
>> modification? Does it allow redistribution? What about
>> relicensing? Are these academic uses of GPC?
> >
> Yest it is so Luke. I've done it others have done it and it works and
> works quite well, there are some changes needed to the ds's to make
> it a faster (as i mentioned previously), and for a fee of a gift to
> the the university of Manchester (which btw is tax deductible if
> you're a resident of the commonwealth) you can change whatever you
> want and redistribute in binary form for commercial purposes on as
> many projects as you like (its even less if you're an indie
> developer).

If the license fee is low enough and only once up front it could be worthwhile. It is a shame you can't share the source code for these modifications. It would be nice if they updated GPC to include them. What did you use as the numerical data type?

>> If fixing everything wrong with GPC is trivial than GPC itself is
>> surely trivail. Why would someone with a commerical purpose in mind
>> start with a for profit license encumbered source code like GPC,
>> which is itself trivial?
> Luke its not all about fixing things that are wrong, merely changing
> some of the underlying assumptions to better suite whatever it is you
> want from the library. Perhaps you might not find it worthwhile, but
> others do. btw if you ever get a chance to see their licensee list
> you'd be quite surprised (wink wink ^M^Mtel) :D

I talked to a fellow Intel engineer last year who said he used GPC ten years ago. His experience was that it failed with a small probability. A small probability across millions of cases added up to tens of thousands of failures, I guess it didn't occur to him to modify it, though few would be able to do that even if it occurred to them to try. I know of no one currently using GPC at Intel, though it is possible; it is a big company.


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