[Qgis-developer] Suppress rendering of small features

Régis Haubourg regis.haubourg at eau-adour-garonne.fr
Fri Sep 13 11:34:25 PDT 2013

I have been following Vincent's solution since I funded #4819 resolution.
Pruning all vertexes under screen resolution is really a nice idea. I wasn't
sure that pruning vertex was less cpu consuming than rendering them, and now
it's proved. just use a very large object, and do a identify on it to see.. 

I think that on the fly vertex pruning is a better definition than
simplification process, since the rendering must be the same when viewed on
screen or on a paper output. 

That bug #4819 occured to be a blocker to us in since new hydro-geological
datasets have a crazy vertex density , and anticipates even more precise
resolutions. All datasets will be derived from high resolution data, but we
always need to render them with small scales.  

I'm wondering if we could something close to raster resampling, with
zoom-out/zoom-in factor and resampling methods (nearest neighbour, bicubic,
average). User could choose the rendering fuzziness factor when zoomed out.
Zoom in is probably something user do not wish (this could lead to bad

Another possible direction I'm thinking of, is having the possibility to
have scale dependent, or better rule based, geometry field. Ie, use full
geometry field when zoomed in, and let user calibrate if other geometry
fields could be used when zoomed out. This is far less generic and elegant
than vertex pruning, but could be usefull with spatialDB, and particular

Let us know what strategic direction you choose, and we can be there to
support you then.

Have good times you all in Brighton. 


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