Geometry Boost List: [ggl] incorrect result for an intersection

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.

Luke