Geometry Boost List: Re: [geometry] Bug again in boost::geometry::union_

Subject: Re: [geometry] Bug again in boost::geometry::union_
From: Barend Gehrels (barend_at_[hidden])
Date: 2014-02-12 10:09:37

Hi Sybren,

Sybren A. Stüvel wrote On 12-2-2014 15:10:
> Hi Barend,
>
> On 12 February 2014 13:46, Barend Gehrels <barend_at_[hidden] 
> <mailto:barend_at_[hidden]>> wrote:
>
>     Good. That warning can be ignored. It's a (more or less personal)
>     development branch. Please comment it in cart_intersect.hpp if you
>     want to get rid of it. I will fix this but it is, for me,
>     diagnostic information
>
>
> I suspected as much. Didn't want to keep any diagnostic info to myself ;-)
>
>     Ah, that is a known problematic side-effect. That has to be fixed
>     too but of course, if you need it today, or even somewhere this
>     week, I cannot do that.
>
>
> Alas, then I'll have to wait a bit more.
>
>     You can try one more thing: please define
>     BOOST_GEOMETRY_NO_ROBUSTNESS. It will than skip all
>     rescaling-to-integer-for-robustness code. That sounds a bit weird,
>     because this thread was to fix that. But besides the rescaling
>     more enhancements have been made, so it might be that your code
>     then runs OK. However, I cannot predict that, there are also cases
>     which really need this rescaling. So you can try how it looks.
>
>
> Unfortunately, that doesn't help. Then I get an empty result at some 
> point - see the attached "exception.svg" file.
>
>     Besides that, maybe even better, you can try to call the function
>     "geometry::remove_spikes" on your output. It hopefully will remove
>     all spikes which are generated.
>
>
> It appears that it doesn't, the spike is still there. I tried this 
> without defining BOOST_GEOMETRY_NO_ROBUSTNESS, as the empty result I 
> described occurs sooner than the generation of any spike.

That is right.

>     Finally, could you also send me the WKT's of your input, for me to
>     check that generated internal spike (as we call it)?
>
>
> I have attached the two inputs (poly0/1) and the result that I get 
> from the union.

Thanks for the info and files. OK, so alas that spike is there for some 
time, sorry for the inconvenience.  I will mail if this is fixed.

Regards, Barend