On 18 May 2016 at 15:57, Lisandro Damián Nicanor Pérez <perezme...@gmail.com> wrote: > Before I try to code a stripped-down version of my issue I would like to > describe it in case I'm missing something obvious. > > I have an app with a QGraphicsScene that holds a vehicle which is constantly > moving at a fixed rate (~10 times per second). Every time it moves it draws > some polygons behind (the path it went trough). Up to that point, everything > is ok. > > Now if I add a lot of straight lines (QGraphicsLineItem instances) performance > (number of movements seen on screen per second) varies according the zoom. If > I zoom in I get to a point in which everything is too slow. If I zoom out > things go back to normal. Note that once the lines are generated they are not > changed in any way. > > I understand that performance might decrease if those lines are near 45º due > to bounding boxes, but I fail to understand why it varies with zoom.
I minimized my code to simple lines and drawing the bounding box of the vehicle, and found out that the problems starts if I use anything different than Qt::SolidLine for drawing the lines. As soon as I zoom out enough (the transformation matrix becoming 0.1*Identity) the problem "goes away", so I suspect a rasterization issue. -- Lisandro Damián Nicanor Pérez Meyer http://perezmeyer.com.ar/ http://perezmeyer.blogspot.com/ _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
