<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12pt"><div><span>You are right, but only if it is possible to generate the quadtree </span><span style="font-size: 12pt;">on the fly</span><span style="font-size: 12pt;"> (millions of points), or preprocess it to disk.</span></div><div style="color: rgb(0, 0, 0); font-size: 12pt; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;">this doc uses a mixed strategy (I used it and it works fine)...</div><div style="background-color:
transparent;">http://www.cs.unc.edu/~isenburg/papers/ilss-scdt-06.pdf<br></div><div><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;">a first pass read the file to build a special quadtree which only save the number of points of each quad-item.</div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;">when the data is readed, it accumulates the points, and when a <span style="font-size: 12pt;">quad-item has all points, then it returns a releases the buffer of this </span><span style="font-size: 12pt;">quad-item.</span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida
Grande', sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;">Alvaro</div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;"><br></div><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; margin-top: 5px; padding-left: 5px;"> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 12pt;"> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 12pt;"> <div dir="ltr"> <hr size="1"> <font size="2" face="Arial"> <b><span
style="font-weight:bold;">De:</span></b> Jean-Roc Morreale <jr.morreale@enoreth.net><br> <b><span style="font-weight: bold;">Para:</span></b> A Huarte <ahuarte47@yahoo.es> <br><b><span style="font-weight: bold;">CC:</span></b> qgis-developer@lists.osgeo.org <br> <b><span style="font-weight: bold;">Enviado:</span></b> Miércoles 29 de enero de 2014 14:25<br> <b><span style="font-weight: bold;">Asunto:</span></b> Re: [Qgis-developer] Lidar data into QGIS<br> </font> </div> <div class="y_msg_container"><br>Most lidar files are not spatially ordered so with a sequential read you <br clear="none">will end up reading the whole file, it's like accessing a untiled <br clear="none">unpyramided bigtiff : painful.<br clear="none"><br clear="none">Le 2014-01-29 13:52, A Huarte a écrit :<br clear="none">> I think but using a quadtree approach there is a problem, and it is<br clear="none">> none other than the construction of the quadtree
itself for so big<br clear="none">> data.<br clear="none">> <br clear="none">> IMHO I would use a specific provider (with a specific featureiterator)<br clear="none">> reading sequentially the LAS file and discarding points before fetch<br clear="none">> it to renderer using the RectangleFilter of current FeatureRequest. It<br clear="none">> avoid create many-many QgsFeature's that after are discarded in<br clear="none">> renderer side.<br clear="none">> <br clear="none">> I use this technique in a personal viewer, and after first read of<br clear="none">> file (the file is cached in SO), the following drawings are quite<br clear="none">> fast.<br clear="none">> <br clear="none">> Alvaro<br clear="none">> <br clear="none">>> -------------------------<br clear="none">>> DE: Jean-Roc Morreale <<a shape="rect" ymailto="mailto:jr.morreale@enoreth.net"
href="mailto:jr.morreale@enoreth.net">jr.morreale@enoreth.net</a>><br clear="none">>> PARA: <a shape="rect" ymailto="mailto:qgis-developer@lists.osgeo.org" href="mailto:qgis-developer@lists.osgeo.org">qgis-developer@lists.osgeo.org</a><br clear="none">>> ENVIADO: Miércoles 29 de enero de 2014 13:32<br clear="none">>> ASUNTO: Re: [Qgis-developer] Lidar data into QGIS<br clear="none">>> <br clear="none">>> Can it performs fast enough to display hundred millions points or<br clear="none">>> billions at once ? Does it leverage a quadtree approach ?<br clear="none">>> <br clear="none">>> Le 2014-01-29 12:55, A Huarte a écrit :<br clear="none">>>> yes, it can be implemented on renderer level (Martin Dobias<br clear="none">>> propose<br clear="none">>>> it) or on featureiterator level similar to current simplification<br clear="none">>>> classes for line and polygons<br
clear="none">>>> <br clear="none">>>> I think it is pending for a test of performance<br clear="none">>>> Best Regards<br clear="none">>>> Alvaro<br clear="none">>> <br clear="none">>> _______________________________________________<br clear="none">>> Qgis-developer mailing list<br clear="none">>> <a shape="rect" ymailto="mailto:Qgis-developer@lists.osgeo.org" href="mailto:Qgis-developer@lists.osgeo.org">Qgis-developer@lists.osgeo.org</a><br clear="none">>> <a shape="rect" href="http://lists.osgeo.org/mailman/listinfo/qgis-developer" target="_blank">http://lists.osgeo.org/mailman/listinfo/qgis-developer </a>[1]<br clear="none">> <br clear="none">> <br clear="none">> <br clear="none">> Links:<div class="yqt3430007822" id="yqtfd45428"><br clear="none">> ------<br clear="none">> [1] <a shape="rect" href="http://lists.osgeo.org/mailman/listinfo/qgis-developer"
target="_blank">http://lists.osgeo.org/mailman/listinfo/qgis-developer</a></div><br><br></div> </div> </div> </blockquote><div></div> </div></body></html>