[Qgis-developer] Geometry precision model

[Andreas Neumann]

Salut Hugo,

I believe that Sourcepole (Sandro Mani) worked on this already - but the 
GEOS patch is pending and was not yet accepted.

See also:
http://trac.osgeo.org/geos/ticket/713
https://lists.osgeo.org/pipermail/geos-devel/2015-January/007080.html

Best to discuss with him - and maybe help to get Sandro Santilli to 
review this patch and hopefully accept it.

Andreas


On 14.09.2015 09:47, Hugo Mercier wrote:
> Hi,
>
> I am investigating a better handling of different precision models
> within QGIS geometry operations, and in particular the "fixed" precision
> model.
>
> Since geometry processing in QGIS relies mostly on GEOS, I think this is
> close to the kind of discussion that can be found in PostGIS:
> https://trac.osgeo.org/postgis/wiki/ToleranceDiscussion
>
> I see it as:
> - storing somewhere as a global parameter, the current precision model
> (in project parameters?), i.e. the current "grid"
> - adding a way to set the "global" precision model to the Geometry API
> - make the Geometry API use this precision model
>
> For the last point, I see two possibilities :
>
> - since we rely on the GEOS C API, which does not allow to modify the
> precision model (always the default - floating), it would require to add
> some new functions in the C API to change the precision model for
> coordinate constructions
>
> - using the C++ GEOS API instead of the C API that exposes precision models.
>
> I am not sure yet about what possibility to implement. Is there anything
> that prevent us from using the C++ GEOS API ? Having it in the C API may
> also benefit to other projects (PostGIS) ...
> Or am I totally missing other problems ?
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