Hi On Wed, Mar 2, 2011 at 11:19 PM, Alister Hood <[email protected]> wrote:
8<-------------snip--------------- >>Hi Tim >> >>yes, it's more costly also for symbols with just one symbol layer. The >>idea is that the features in current view are loaded into memory first >>(with a reference to symbol that will be used) and then rendered. So >>there is some memory overhead and some cpu overhead (unsure about the >>total amount). The case with just one symbol layer could be probably >>optimized to some degree. > > Are you sure it needs to be optimised? When there is only one symbol > layer the final appearance always seems to be the same, whether symbol > layers are turned on or not. If this is the case, couldn't symbol > layering just be ignored when there is only one? > Am I missing something? > > Alister > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > Alister from my understanding of it, even if there is a single layer, with layer levels turned on, QGIS tries to load all the features into memory first resulting in some overhead. I suspect in some situations this may actually render *quicker* (untested) but for large datasets where a lot of swapping out of ram to disk needs to happen, it could kill performance somewhat. The optimisation in this case may simply be 'if there is one layer level. render as if layer levels are disabled'. Martin may have further comments. Regards Tim -- Tim Sutton - QGIS Project Steering Committee Member (Release Manager) ============================================== 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. Visit http://linfiniti.com to find out about: * QGIS programming and support services * Mapserver and PostGIS based hosting plans * FOSS Consulting Services Skype: timlinux Irc: timlinux on #qgis at freenode.net ============================================== _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
