[Qgis-developer] On the fly simplication of point layers

[A Huarte]

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 ?

Alvaro


>________________________________
> De: Tim Sutton <lists at linfiniti.com>
>Para: Martin Dobias <wonder.sk at gmail.com> 
>CC: qgis-developer <qgis-developer at lists.osgeo.org>; "tech at wildintellect.com" <tech at wildintellect.com> 
>Enviado: Jueves 23 de enero de 2014 23:16
>Asunto: Re: [Qgis-developer] On the fly simplication of point layers
> 
>
>
>Hi
>
>
>
>On Wed, Jan 22, 2014 at 2:47 PM, Tim Sutton <lists at linfiniti.com> wrote:
>
>Hi
>>
>>
>>
>>On Wed, Jan 22, 2014 at 1:23 PM, Martin Dobias <wonder.sk at gmail.com> wrote:
>>
>>On Wed, Jan 22, 2014 at 4:33 PM, Tim Sutton <lists at linfiniti.com> wrote:
>>>>>
>>>>> Actually the point displacement renderer already does clustering,
>>>>> though it lacks more options to customize how the clustered symbol
>>>>> would look like.
>>>>>
>>>>
>>>> Doesnt it do the reverse? i.e. when more than one point falls in the same
>>>> place, it shifts them aside so they are all visible. If it can be made to
>>>> produce a scaled symbol based on the number of underlying points that would
>>>> be cool.That would also be a good time to change its name to 'Custer or
>>>> displace' or something.
>>>
>>>I think that was what the renderer did originally, but nowadays it
>>>also groups points within configured distance. Unfortunately it always
>>>tries to draw a circle around the clustered point with original
>>>symbols. If we introduced few rendering options, it would be more
>>>useful:
>>>- draw just the clustered symbol for the whole group
>>>- scale the clustered symbol depending on the number of points inside
>>>
>>>
>>
>>
>>Yeah that should do it!
>>
>>
>
>
>I tested with a large point dataset (geonames ~3.5 million records). Basically enabling the point displacement renderer on that layer kills (or takes so long I killed it) QGIS. Since the essence of clustering is to speed up rendering times and reduce visual clutter, I suspect simple tweaks to the renderer would not be enough.
>
>
>Regards
>
>
>Tim
>
>
> 
>Regards
>>
>>
>>Tim
>> 
>>Cheers
>>>Martin
>>>
>>
>>
>>
>>
>>-- 
>>
>>Tim Sutton - QGIS Project Steering Committee Member
>>==============================================
>>Please do not email me off-list with technical
>>support questions. Using the lists will gain
>>more exposure for your issues and the knowledge
>>surrounding your issue will be shared with all.
>>
>>Irc: timlinux on #qgis at freenode.net
>>
>>==============================================
>
>
>
>
>-- 
>
>Tim Sutton - QGIS Project Steering Committee Member
>==============================================
>Please do not email me off-list with technical
>support questions. Using the lists will gain
>more exposure for your issues and the knowledge
>surrounding your issue will be shared with all.
>
>Irc: timlinux on #qgis at freenode.net
>==============================================
>
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