# Geometry :

Subject: Re: [geometry] boost::geometry::difference problem
From: h2 (account.h.horiuchi_at_[hidden])
Date: 2012-10-10 22:01:01

Hi Barend.

2 patterns that I know,
only that the problem could be avoided if giving priority to the "ix",
It will be only the reference level, you will be reported.

Once, I try to find other cases.

Best Regards.
h2

2012/10/11, Barend Gehrels <barend_at_[hidden]>:
> 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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