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Rotation of an image (in a loop) is not smooth although the fps is 60



  • I tried two different possibilities.

    First:

    @Image
    {
    id: media_cover
    source: "../images/media_cover.png"
    smooth: true
    rotation: 0
    transformOrigin: Item.Center
    }@

    @RotationAnimation
    {
    target: media_cover;
    property: "rotation";
    loops: Animation.Infinite;
    from: 0;
    to: 360;
    duration: 8000
    } @

    Second:

    @ Image
    {
    id: media_cover
    source: "../images/media_cover.png"
    smooth: true

            transform:
                Rotation {
                id: cover_rot
                origin.x: parent.width/2
                origin.y: parent.width/2
                angle: 0
                }
    

    }
    @

    @NumberAnimation
    {
    target: cover_rot;
    property: "angle";
    loops: Animation.Infinite;
    from: 0;
    to: 360;
    duration: 8000
    }
    @

    Both options don't work.

    I tried it on windows xp, windows 7, i.MX53 with Qt 4.8 and also with Qt 5 Alpha. Everywhere with the same result.

    Is it a known problem of Qt or rather someone knows a solution for this problem.


  • Moderators

    AFAIK, it is a known problem, it was discussed a while ago on dev mailing list. Try porting to QtQuick2 if possible, just to see if it is still a problem there. On the other hand, animations are not smooth with QML2 on Linux... but maybe that was fixed, too.



  • The perceived smoothness has to do with synchronization of the renderings with the updates of the screen by the underlying system (OpenGL, for instance). At least, that is how I understood the issue. See "this post":http://labs.qt.nokia.com/2010/12/02/velvet-and-the-qml-scene-graph/ for example.



  • Thank You for your answers, I forget to say that i tried it with QtQuick 2.0, too. There is the same Problem.


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