[Qgis-user] Buffer segments to approximate

[Ludovic Granjon]

Dear Andreas, Horst
Thanks a lot for your answers, it's perfect.
Maybe it could be interesting to insert this kind of things in the 
documentation ?
Ludovic

Le 19/11/2013 17:29, Horst Düster a écrit :
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> Hi Ludovic
>
> The number of segments depends on the exactness of the results you
> expect. If you create a circle buffer around a point with radius of 1
> the area of the circle will running against PI with increasing number of
> segments. Now you have to decide how many digits of PI are expected as
> exact.
>
>
> mPoint = QgsGeometry().fromPoint(QgsPoint(0,0))
> for i in range(100):
>      circle = mPoint.buffer(1,i+1)
>      print str(i)+"  "+str(circle.area())
>
>
> All the best
> Horst
>
>   
>
> Dr. Horst Düster
> Kappasys
> Alte Bernstrasse 13
> CH-4500 Solothurn
>
> Tel.: +41 (0) 32 514 00 40
> Mobil: +41 (0) 76 408 51 06
> eMail: horst.duester at kappasys.ch
> skype: horstduester
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>
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>
> Am 19.11.2013 17:07, schrieb Andreas Neumann:
>> Hi,
>>
>> Buffers for points are round. There are also round corners for
> line/polygon buffers, depending on the linecap styles and line join
> styles. QGIS and simple features can only display straight lines. The
> number of the segements to approximate means the higher the number, the
> more vertices you will have for a circle approximation.
>> See also http://postgis.net/docs/manual-2.1/ST_Buffer.html as an
> explanation for buffer styles and segments.
>> Andreas
>>
>> Am 2013-11-19 14:57, schrieb ludo:
>>> Hi all
>>>
>>> Is there anyone could tell me what is "segments to approximate" in the
>>> buffer tool ?
>>>
>>> I know that if I increase this value, there's more nodes on my buffer
>>> but I don't know what is it exactly and how we can choose this value.
>>>
>>> Thanks
>>>
>>> Regards
>>>
>>> Ludovic
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>>> Qgis-user mailing list
>>> Qgis-user at lists.osgeo.org
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