# Geometry :

Subject: Re: [geometry] boost::geometry::difference problem
From: Barend Gehrels (barend_at_[hidden])
Date: 2012-10-10 12:18:41

Hi H2,

I can reproduce your problem exactly and it is a strange problem. Will
look in more detail.

Regards, Barend

On 9-10-2012 15:02, horiuchi wrote:
> Hi,
>
> There is no way I would support and measures?
> **Since the story is pretty basic operation,
> We understand that the impact is strong.
>
> Best Regards.
> h2
>
> (2012/09/15 16:38), Barend Gehrels wrote:
>> Hi,
>> Sorry - I'm off, have to answer this next weekend.
>> Regards, Barend
>>
>> On 14-9-2012 15:54, h2 wrote:
>>> Hi.
>>>
>>> I am troubled by funny behavior of boost::geometry::difference.
>>> Two cases below should be the same, but a different result comes back.
>>>
>>> *OK
>>> geometry1 MULTIPOLYGON(((-2 5, -1 5, 0 5, 2 5, 2 -2, 1 -2, 1 -1, 0 -1,
>>> 0 0, -1 0, -2 0, -2 5)))
>>> geometry2 MULTIPOLYGON(((0 0, 1 0, 1 -1, 0 -1, 0 0)), ((-1 5, 0 5, 0
>>> 0, -1 0, -1 5)))
>>> output MULTIPOLYGON(((0.0 5.0,2.0 5.0,2.0 -2.0,1.0 -2.0,1.0 -1.0,1.0
>>> 0.0,0.0 0.0,0.0 5.0)),((-1.0 5.0,-1.0 0.0,-2.0 0.0,-2.0 5.0,-1.0
>>> 5.0)))
>>>
>>> *NG
>>> geometry1 MULTIPOLYGON(((-2 5, -1 5, 0 5, 2 5, 2 -2, 1 -2, 1 -1, 0 -1,
>>> 0 0, -1 0, -2 0, -2 5)))
>>> geometry2 MULTIPOLYGON(((-1 5, 0 5, 0 0, -1 0, -1 5)), ((0 0, 1 0, 1
>>> -1, 0 -1, 0 0)))
>>> output MULTIPOLYGON(((-1.0 5.0,-1.0 0.0,-2.0 0.0,-2.0 5.0,-1.0 5.0)))
>>>
>>> As for the difference of both, polygon order of geometry2 is only
>>> reversed.
>>>
>>> I traced a program,
>>> Was found to be a pattern that is not supported by
>>> boost::geometry::detail::overlay::sort_in_cluster::operator().
>>> (geometry/algorithms/detail/overlay/handle_tangencies.hpp)
>>>
>>> The pattern that developed is "ix/xi".
>>>
>>> Will you know a correspondence method for this behavior?
>>> If there is advice, I am happy,
>>> and sorry for my english (not a native speaker. Therefore, I'm using a
>>>
>>> Best Regards.
>>> h2
>>> _______________________________________________
>>> Geometry mailing list
>>> Geometry_at_[hidden]

>>>
>>
>>
>
>

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