You are right, but only if it is possible to generate the quadtree on the fly
(millions of points), or preprocess it to disk.
this doc uses a mixed strategy (I used it and it works fine)...
http://www.cs.unc.edu/~isenburg/papers/ilss-scdt-06.pdf
a first pass read the file to build a special quadtree which only save the
number of points of each quad-item.
when the data is readed, it accumulates the points, and when a quad-item has
all points, then it returns a releases the buffer of this quad-item.
Alvaro
>________________________________
> De: Jean-Roc Morreale <jr.morre...@enoreth.net>
>Para: A Huarte <ahuart...@yahoo.es>
>CC: qgis-developer@lists.osgeo.org
>Enviado: Miércoles 29 de enero de 2014 14:25
>Asunto: Re: [Qgis-developer] Lidar data into QGIS
>
>
>Most lidar files are not spatially ordered so with a sequential read you
>will end up reading the whole file, it's like accessing a untiled
>unpyramided bigtiff : painful.
>
>Le 2014-01-29 13:52, A Huarte a écrit :
>> I think but using a quadtree approach there is a problem, and it is
>> none other than the construction of the quadtree itself for so big
>> data.
>>
>> IMHO I would use a specific provider (with a specific featureiterator)
>> reading sequentially the LAS file and discarding points before fetch
>> it to renderer using the RectangleFilter of current FeatureRequest. It
>> avoid create many-many QgsFeature's that after are discarded in
>> renderer side.
>>
>> I use this technique in a personal viewer, and after first read of
>> file (the file is cached in SO), the following drawings are quite
>> fast.
>>
>> Alvaro
>>
>>> -------------------------
>>> DE: Jean-Roc Morreale <jr.morre...@enoreth.net>
>>> PARA: qgis-developer@lists.osgeo.org
>>> ENVIADO: Miércoles 29 de enero de 2014 13:32
>>> ASUNTO: Re: [Qgis-developer] Lidar data into QGIS
>>>
>>> Can it performs fast enough to display hundred millions points or
>>> billions at once ? Does it leverage a quadtree approach ?
>>>
>>> Le 2014-01-29 12:55, A Huarte a écrit :
>>>> yes, it can be implemented on renderer level (Martin Dobias
>>> propose
>>>> it) or on featureiterator level similar to current simplification
>>>> classes for line and polygons
>>>>
>>>> I think it is pending for a test of performance
>>>> Best Regards
>>>> Alvaro
>>>
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>>> Qgis-developer@lists.osgeo.org
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>>
>>
>>
>> Links:
>
>> ------
>> [1] http://lists.osgeo.org/mailman/listinfo/qgis-developer
>
>
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