[Qgis-developer] Approximate reprojection for vectors

[Marco Hugentobler]

Hi Radim

Am Sonntag, 2. Oktober 2011, 17.34:48 schrieb Radim Blazek:
> You are right. I have done some tests and rendering with reprojection
> takes obnly about 10% more time. I was convinced that it must be quite
> time consuming. In fact, reprojection is a complex caclulation so I am
> wondering  what can take so long time in rendering process so that the
> reprojection is not significant.

It depends a lot on the map to render.

I did a lot of profiling for the FOSS4G WMS benchmark (osm data, reprojected to 
google crs, complex symbology with a lot of rules). The pattern was mostly the 
following:
the rendering itself (QPainter->drawPolyline) was the most time consuming 
operation (appr. 50% of rendering time), next was evaluation in rule based 
renderer (20% of time), getNextFeature in PostgresProvider 10%, coordinate 
transformation 10%.

Regards,
Marco

> 
> Radim
> 
> On Sun, Oct 2, 2011 at 3:02 PM, cavallini at faunalia.it
> 
> <cavallini at faunalia.it> wrote:
> > I do not see reprojection of vectors significantly slowing down
> > rendering. Anyone does?
> > All the best.
> > 
> > http://faunalia.it/pc
> > 
> > ----- Reply message -----
> > Da: "Radim Blazek" <radim.blazek at gmail.com>
> > A: "qgis-developer" <qgis-developer at lists.osgeo.org>
> > Oggetto: [Qgis-developer] Approximate reprojection for vectors
> > Data: dom, ott 2, 2011 14:40
> > 
> > 
> > Hi,
> > as you probably know, raster reprojection is using approximate
> > reprojection to get acceptable rendering speed. Now I am thinking
> > about a possibility to implement the same also for vectors, to speed
> > up vectors rendering. What do you think about that? Does it make
> > sense?
> > 
> > Radim
> > _______________________________________________
> > Qgis-developer mailing list
> > Qgis-developer at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/qgis-developer
> 
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