QML Entity Transform doesn't change from C++ Q_PROPERTY

[Alien]

Hello,

I implemented the below code in QML:

    Entity
    {
        id: birdModelID

        property real x: 0.0
        property real y: 0.0
        property real z: 0.0
        property real scale: 0.018

        property real pitch: CPP_CLASS.pitch
        property real yaw: CPP_CLASS.yaw
        property real roll: CPP_CLASS.roll

        Transform
        {
            id: transformID
            translation: Qt.vector3d(birdModelID.x, birdModelID.y, birdModelID.z)
            rotation: fromEulerAngles(birdModelID.pitch, birdModelID.yaw, birdModelID.roll)
            scale: birdModelID.scale
        }
        Mesh
        {
            id: meshbirdID
            source: "qrc:/3DAssets/bird.obj"
        }

        PhongMaterial
        {
            id:materialID
            ambient: "lime"
        }

        components: [meshbirdID,transformID, materialID ]
    }

When roll,pitch,yaw change in C++ (CPP_CLASS) my 3D model doesn't change in QML?

[ODБOï]

hi
@alien said in QML Entity Transform doesn't change from C++ Q_PROPERTY:

When roll,pitch,yaw change in C++ (CPP_CLASS) my 3D model doesn't change in QML?

1. make sure your Q_PROPERTY has the NOTIFY macro
2. make sure, when you change the value of a variable, to emit corresponding <variable name>Changed() signal

[Alien]

Dear @lelev,
It has NOTIFY macro also the set function emit corresponding change signal but transform doesn't change my 3D model.

[KroMignon]

@alien Can you show use in which way you have declared pitch, yaw, roll and how you have exposed CPP_CLASS to QML?

I should be something like this:

class CppClass : public QObject
{
    Q_OBJECT

     Q_PROPERTY(qreal pitch READ pitch  NOTIFY pitchChanged)
     Q_PROPERTY(qreal yaw   READ yaw    NOTIFY yawChanged)
     Q_PROPERTY(qreal roll  READ roll   NOTIFY rollChanged)
   
public:
    explicit CppClass(QObject * parent = nullptr): QObject(parent) {}

    qreal pitch() const { return m_pitch; }
    qreal yaw() const { return m_yaw; }
    qreal roll() const { return m_roll; }
    
    void updatePitch(qreal pitch)
    {
        if(!qFuzzyCompare(m_pitch, pitch))
        {
            m_pitch = pitch;
            emit pitchChanged(pitch);
        }
    }
    void updateYaw(qreal yaw)
    {
        if(!qFuzzyCompare(m_yaw, yaw))
        {
            m_yaw = yaw;
            emit pitchChanged(yaw);
        }
    }
    void updateRoll(qreal roll)
    {
        if(!qFuzzyCompare(m_roll, roll))
        {
            m_roll = roll;
            emit rollChanged(roll);
        }
    }

signals:
    void pitchChanged(qreal pitch);
    void yawChanged(qreal yaw);
    void rollChanged(qreal roll);
};

Then export your instance to QML context:

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    
    // register instance in QML context
    CppClass myCppClass;
    engine.rootContext()->setContextProperty("CPP_CLASS", &myCppClass);

    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

[Alien]

@kromignon thanks for your reply ,does it works for you?
I use the same cpp code except that I don't pass any argument to change signals! Does it matter to pass argument to change signals?

[KroMignon]

@alien Signal do not need to have an argument. And yes, this works for me... But I don't use Qt3D.

You can try to add some debug to see if value change arrives QML:

Entity {
        id: birdModelID

        property real x: 0.0
        property real y: 0.0
        property real z: 0.0
        property real scale: 0.018

        property real pitch: CPP_CLASS.pitch
        onPitchChanged: console.log("Pitch has changed to " + pitch)
        property real yaw: CPP_CLASS.yaw
        onYawChanged: console.log("Yaw has changed to " +yaw)
        property real roll: CPP_CLASS.roll
        onRollChanged: console.log("Roll has changed to " + roll)

...
}

[Alien]

@kromignon Thanks for your reply the problem comes from defining CPP_Class attributes as a float instead of qreal after changing float to qreal it works.

I appreciate your reply and time