Hi Martin, So you think the same code of the point displacement renderer can also be used for clustering?
It was developed exactly for the opposite: if multiple geometries are on top of each other they are displaced so you can see all of the points. A use-case is where several people live at the same address but have different attributes and you want to see them all. I am a bit surprised that the same code could be used for the opposite - to cluster points that are not at the same position. Wouldn't it require some additional code/work to do that? Just wondering. Andreas Am 24.01.2014 09:29, schrieb Martin Dobias: > Hi Tim > > On Fri, Jan 24, 2014 at 2:31 PM, Tim Sutton <[email protected]> wrote: >> On Fri, Jan 24, 2014 at 1:12 AM, A Huarte <[email protected]> wrote: >>> >>> Hi! >>> >>> About simplification (no clustering), I think that the If we discard >>> points based on the distance to the last fetched and rendered point >>> (https://github.com/qgis/QGIS/blob/master/src/core/qgsfeatureiterator.cpp#L36) >>> it will be very effective to render big dense points layers. I have a GIS >>> application using this technique and it draws LAS files (> 30mb) "fast". >>> >>> I would like write a "point simplifier" in QGIS to validate results. >>> Do you agree ? >> >> >> I think this would be great. Since you are doing a full scan of the dataset, >> you should be able to count how many points each aggregate point represents >> right? I was thinking we could pass that the the renderer as a 'virtual' >> attribute so that we can use it to e.g. scale the symbol size. >> >> +1 from me to implement this anyway as a new cluster renderer (or a patch >> the point displacement renderer if that seems workable). > > Actually in the threading branch I have significantly reworked the way > how the clustering is done in the point displacement renderer. A quick > test with ~75K points shows that QGIS 2.0 takes ~10 minutes to render > with point displacement, while in threading branch it is matter of a > second or two. In the threading branch the renderer uses spatial index > for clustering. Another optimization could be to build the spatial > index for a layer just once, for even better performance. > > So I believe now it's mainly a matter of adding more configuration > options.to allow output similar to "usual" marker clustering - and > make such options default. > > I would prefer not to have "point simplifier" somewhere in the data > access API - like Tim suggests, it is best to keep such functionality > in a renderer. > > Regards > Martin > _______________________________________________ > Qgis-developer mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-developer > _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
