[Interest] Rotating objects in QML are killing performance

[Michael Andersen]

> Is vsync enabled in your driver? Sounds like it might not be. If not, then
> Qt Quick 2.0 will render at 100% cpu rendering maybe many thousands of
> frames per second, even though you only see 60 of them.
>

Unfortunately, VSync is enabled, that would have been a good explanation.

I am using the Nvidia binary drivers (v304.51) so in order to double check
that applications actually *were* vsynced, I ran glxgears. Turns out that
glxgears does the same thing: no repainting while dragging and it lags the
whole PC when you drag the app. This is not a small PC, I have a GTX 560
Ti, 32GB of ram and an i7 3930.. why oh why is glxgears lagging...

For want of another data point, I ran minecraft, yes I know its a different
language and all that, but it does have an OpenGL context... and it doesn't
lag the pc at all while the window is being dragged.

So I am not sure that this is really Qt's fault, except that the QtQuick
1.1 application did not exhibit the same problems, and it does seem
possible to make an OpenGL application that repaints while the window is
moved.

Any ideas?


> cheers,
> Gunnar
>
> >
> > Here is a simple reproducer of the problem, I create a QtQuick2
> application in Qt Creator 2.7. I adjust the QML to look like this:
> >
> > import QtQuick 2.0
> >
> > Rectangle {
> >     width: 400
> >     height: 400
> >     Rectangle {
> >         id: redsquare
> >         color: "red"
> >         width: 50
> >         height: 50
> >         x: 50
> >         y: 50
> >     }
> >     RotationAnimation {
> >         loops: Animation.Infinite
> >         target: redsquare
> >         properties: "rotation"
> >         from: 0
> >         to: 360
> >         duration: 300*5
> >         direction: RotationAnimation.Clockwise
> >         running: true
> >     }
> > }
> >
> > My main.cpp is the default, but that looks like this:
> >
> > #include <QtGui/QGuiApplication>
> > #include "qtquick2applicationviewer.h"
> >
> > int main(int argc, char *argv[])
> > {
> >     QGuiApplication app(argc, argv);
> >
> >     QtQuick2ApplicationViewer viewer;
> >     viewer.setMainQmlFile(QStringLiteral("qml/SimpleRotator/main.qml"));
> >     viewer.showExpanded();
> >
> >     return app.exec();
> > }
> >
> > I am new to Qt, so perhaps I am doing something wrong with my animation,
> but I have tried a couple other methods of animating and they all lag
> equally badly. The PC I develop on is quite a monster, so if it is lagging
> on this, I hate to think what it's going to do on my clients' laptops.
> >
> > Anyone have any ideas?
> >
> > Regards
> > Michael
> > _______________________________________________
> > Interest mailing list
> > Interest at qt-project.org
> > http://lists.qt-project.org/mailman/listinfo/interest
>
>
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