QT C++ loading a mesh having multiple material

Gilboonet

Hello, now that the 2D part of my application is ok, I'm working on the 3D part, a 3d scene showing the 3d model with each unfolded part (the purpose of my application) shown in its own color. I managed to use the QT 3D C++ simple example code to display the 3d model (an .obj file), but it only display it with everything using the first material when I expected it to use 4. Is there something to do to handle such multiple material model ?

If needed I could create one QEntity for each material and put a QGeometry with the vertices and the triangles, but for the moment I didn't find how to create a QGeometry from scratch.

I'm hoping to use this 3D view to not only view the model as I unfold it, but also be able to handle triangle picking, but I know that I'm a long way from there.

Does someone have any hint for me ?

my code :

Qt3DCore::QEntity *createScene()
{
    // Root entity
    Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity;

    // Material
    Qt3DExtras::QGoochMaterial *mat1 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat1->setCool(QColor(Qt::white));
    Qt3DExtras::QGoochMaterial *mat2 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat2->setCool(QColor(Qt::blue));
    Qt3DExtras::QGoochMaterial *mat3 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat3->setCool(QColor(Qt::green));
    Qt3DExtras::QGoochMaterial *mat4 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat4->setCool(QColor(Qt::red));

    // Volume
    Qt3DCore::QEntity *Entity = new Qt3DCore::QEntity(rootEntity);
    Qt3DRender::QMesh *volumeMesh = new Qt3DRender::QMesh();
    volumeMesh->setSource(QUrl::fromLocalFile("/home/gigi/Documents/modeles/assets/tdy186_4C.obj"));

    // Orbit Transform
    Qt3DCore::QTransform *sphereTransform = new Qt3DCore::QTransform;
    OrbitTransformController *controller = new OrbitTransformController(sphereTransform);
    controller->setTarget(sphereTransform);
    controller->setRadius(1.0f);

    Entity->addComponent(mat1);
    Entity->addComponent(mat2);
    Entity->addComponent(mat3);
    Entity->addComponent(mat4);
    Entity->addComponent(volumeMesh);
    Entity->addComponent(sphereTransform);

    return rootEntity;
}

Gilboonet

I have this model

I saved it into 4 differents files each of them having only triangles of one color, then I tried to load them into my scene but apparently only the last mesh appears. I tried to use separated material for each mesh, then the same one for them all, but only the last mesh appears. There is certainly something that I didn't get.

here's what my code does

Qt3DCore::QEntity *createScene()
{
    // Root entity
    Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity;

    // Material
    Qt3DExtras::QGoochMaterial *mat1 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat1->setCool(QColor(Qt::white));
    Qt3DExtras::QGoochMaterial *mat2 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat2->setCool(QColor(Qt::blue));
    Qt3DExtras::QGoochMaterial *mat3 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat3->setCool(QColor(Qt::green));
    Qt3DExtras::QGoochMaterial *mat4 = new Qt3DExtras::QGoochMaterial(rootEntity);
    mat4->setCool(QColor(Qt::red));

    // Volume
    Qt3DCore::QEntity *Entity = new Qt3DCore::QEntity(rootEntity);
    Qt3DRender::QMesh *volumeMesh1 = new Qt3DRender::QMesh();
    volumeMesh1->setSource(QUrl::fromLocalFile("/home/gigi/Documents/modeles/assets/tdy186_4C_1.obj"));
    Qt3DRender::QMesh *volumeMesh2 = new Qt3DRender::QMesh();
    volumeMesh2->setSource(QUrl::fromLocalFile("/home/gigi/Documents/modeles/assets/tdy186_4C_2.obj"));
    Qt3DRender::QMesh *volumeMesh3 = new Qt3DRender::QMesh();
    volumeMesh3->setSource(QUrl::fromLocalFile("/home/gigi/Documents/modeles/assets/tdy186_4C_3.obj"));
    Qt3DRender::QMesh *volumeMesh4 = new Qt3DRender::QMesh();
    volumeMesh4->setSource(QUrl::fromLocalFile("/home/gigi/Documents/modeles/assets/tdy186_4C_4.obj"));

    // Orbit Transform
    Qt3DCore::QTransform *sphereTransform = new Qt3DCore::QTransform;
    OrbitTransformController *controller = new OrbitTransformController(sphereTransform);
    controller->setTarget(sphereTransform);
    controller->setRadius(1.0f);

    Entity->addComponent(volumeMesh1);
    //Entity->addComponent(mat1);
    Entity->addComponent(volumeMesh2);
    //Entity->addComponent(mat2);
    Entity->addComponent(volumeMesh3);
    //Entity->addComponent(mat3);
    Entity->addComponent(volumeMesh4);
    //Entity->addComponent(mat4);
    Entity->addComponent(mat1);
    Entity->addComponent(sphereTransform);

    return rootEntity;
}

Gilboonet

Well, I managed to make it work by loading my .obj file as a scene and not as a mesh. My textures need to be better defined but it it promising for me.

Qt3DCore::QEntity *createScene()
{
    // Root entity
    Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity;
    Qt3DCore::QEntity *Entity = new Qt3DCore::QEntity(rootEntity);
    Qt3DRender::QSceneLoader *sceneLoader = new Qt3DRender::QSceneLoader(Entity);
    sceneLoader->setSource(QUrl::fromLocalFile("/home/gigi/Documents/modeles/assets/tdy186_4C.obj"));

    // Orbit Transform
    Qt3DCore::QTransform *sphereTransform = new Qt3DCore::QTransform;
    OrbitTransformController *controller = new OrbitTransformController(sphereTransform);
    controller->setTarget(sphereTransform);
    controller->setRadius(1.0f);

    Entity->addComponent(sceneLoader);
    Entity->addComponent(sphereTransform);

    return rootEntity;
}

Gilboonet

Now that it's ok, I'm wondering whether is is possible to directly use a QByteArray or anything else instead of a file as on my application I edit the model graphically and would like to be able to reflect any change I make to the unfolded 2D pattern to the 3D View. In fact write the file won't take long but it would be great to avoid it.