[Qgis-user] Buffer segments to approximate

[Horst Düster]

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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

 

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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
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-user
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