Geometry Boost List: [ggl] Difference / xor for multi polygons

Subject: [ggl] Difference / xor for multi polygons
From: Barend Gehrels (barend)
Date: 2011-03-06 16:36:03

Hi Javier,

OK, should be solved now. A little complex to explain, but it was a 
robustness problem in coordinate intersection, by which a wrong 
intersection point was generated. I didn't touch that file for a long 
time so I'm glad this is solved now - I've to study it for possibly 
similar cases. Your case is added to the testsuite to prevent happening 
again, thanks for it.

So what I told earlier is wrong, for float it was OK because not exactly 
triggered by the problem above, for ttmath these kind of things should 
not occur, and for double this one is solved now.

Hoping you can continue now, but in case of more problems, reports are 
welcome, I appreciate your tests.

Regards, Barend

On 6-3-2011 18:17, Barend Gehrels wrote:
> Hi Javier,
>
> Right, now I get the same. The error occurs only for double. For float 
> it is OK (but that is by chance), for ttmath it is also OK (that is as 
> intended). The differences in coordinates are so small that for double 
> they probably cannot be represented, but this is my preliminary 
> conclusion. I will check if I can get extra information, and if there 
> are even possible solutions. This can take me a while.
>
> For checking coordinates like this, I would advice to use ttmath.
>
> Interesting tests.
>
> Regards, Barend
>
>

-- 
Barend Gehrels
http://about.me/barendgehrels