[Interest] Strange flicker when moving a camera with the mouse in Qt Quick 3D

[joao morgado]

Hi
I have a View3D with MouseArea on top, I'm moving a camera when pressing and moving the mouse. It works but I get a strange flicker because of mapTo3DScene() strange results. 
A small example project is here 

CameraMove.zip


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CameraMove.zip


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Relevant code of moving the camera is here:
    property vector3d mousePosition
    property vector3d worldPos3D_old: worldPos3D
    property vector3d worldPos3D
    property vector3d cameraPos

    //! [mouse area]
    MouseArea {
        id: ma
        anchors.fill: view
        //! [mouse area]

        onPressed: {
            cameraPos = mainCamera.position
            mousePosition = Qt.vector3d(mouseX, mouseY, 0)
            worldPos3D_old = worldPos3D = view.mapTo3DScene(mousePosition)
        }
        
        onMouseYChanged: {
            updateCamera(mouseX, mouseY)
        }

        function updateCamera( mouseX_,  mouseY_){
            mousePosition = Qt.vector3d(mouseX_, mouseY_, 0)
            worldPos3D = view.mapTo3DScene(mousePosition)
            console.log("worldPos3D: "+worldPos3D + " ; mousePosition: "+mousePosition )
            mainCamera.position.x = cameraPos.x - worldPos3D.x + worldPos3D_old.x
            mainCamera.position.y = cameraPos.y - worldPos3D.y + worldPos3D_old.y
            //mainCamera.position = cameraPos - worldPos3D + worldPos3D_old

        }

    }//MouseArea

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The lines
mousePosition = Qt.vector3d(mouseX_, mouseY_, 0)
 console.log("worldPos3D: "+worldPos3D + " ; mousePosition: "+mousePosition )
shows me strange values, when moving the mouse,  in worldPos3D returned by mapTo3DScene(), see below
qml: worldPos3D: QVector3D(152.83, 7.24083, 190) ; mousePosition: QVector3D(568.372, 216.524, 0)
qml: worldPos3D: QVector3D(141.141, 1.82567, 190) ; mousePosition: QVector3D(568.372, 216.88, 0)
qml: worldPos3D: QVector3D(152.474, 7.24082, 190) ; mousePosition: QVector3D(568.016, 216.88, 0)
qml: worldPos3D: QVector3D(140.785, 1.46959, 190) ; mousePosition: QVector3D(567.66, 217.237, 0)
qml: worldPos3D: QVector3D(152.117, 6.88474, 190) ; mousePosition: QVector3D(567.304, 217.593, 0)
qml: worldPos3D: QVector3D(140.428, 1.46959, 190) ; mousePosition: QVector3D(566.948, 217.593, 0)
qml: worldPos3D: QVector3D(151.761, 6.17257, 190) ; mousePosition: QVector3D(566.592, 218.305, 0)
qml: worldPos3D: QVector3D(140.072, 1.1135, 190) ; mousePosition: QVector3D(566.236, 218.661, 0)

See the last 3 values of mousePosition for example, the x value, they show  coerent mouse move: 
566.948 -> 566.592 -> 566.236But the equivalent world coordinates stored in worldPos3D by mapTo3DScene() make no sense to me:140.428 -> 151.761 ->140.072
The values are leaping wich explain the huge flicker. Any ideias why I get these strange values ?
ThanksJoão
 




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