[Qgis-user] Simple curves

[Andreas Neumann]

Hi Marco,

When you say "curves" - do you mean "circular arcs" - I assume.

Yes - it is possible.

If you want to preserve curves, you'd have to choose a data provider 
capable of storing curves. At the moment, the only two data formats with 
curves supported in QGIS, are Postgis and Geopackage, provided that you 
have a recent version of GDAL and QGIS. Editing curves is part of the 
normal editing tools (advanced digitizing toolbar). Maybe GML support 
curves - but I don't think you can edit GML in OGR/QGIS - I may be wrong 
though.

However, you could create curves also for data providers that don't 
support curves. In that case your curve gets segmented into many short 
lines - and as a consequence, you can't edit the curve efficiently, once 
it is created.

There is, however, a drawback if you use curves - basically whenever you 
do something geometry-related, other than plain editing or display of 
the data, it will be stroked - e.g. if you split or merge a feature 
containing curves, it will be - again be segementized. This is because 
the underlying geometry libraries (GEOS) can't handle curves. In such 
cases where GEOS is used, QGIS has to segmentize the data before feeding 
it into GEOS.

Greetings,

Andreas


On 17.04.2018 16:07, Marco Dinges wrote:
> Hey guys,
>
> is it possible to create simple curves with, for example, three Points 
> and a radius?
>
>
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