How can I load a 3D model(like *.obj files etc.) in QT

[z69333186]

HI,
Now, I am doing a project in which I want to display a 3D model(robot) and control it like moving its leg or arm.
So, I am trying to load a *.obj files into QT, but I failed.
I search on the Internet and some people say I can try the Assimp, but i can't find how to use it. I include <AssimpIO> but resulted in a "file not found" compiler error. it seems QT do not support Assimp now?
Is there any way to load 3D model(like *.obj files etc.) into QT?

[SGaist]

Hi and welcome to devnet,

Did you took a look at the Qt3D module documentation and the accompanying examples ?

The Audio Visualizer Example loads .obj files.

By the way, it's Qt. QT stands for Apple QuickTime which doesn't seem to be what you are looking for.

[z69333186]

This post is deleted!

[z69333186]

@SGaist Thank you very much. Acctually I want find a example using C++ to load 3D model, but the Audio Visualizer Example still help me a lot. I will study this example carefully.
I still very much appreciate your help~

[jiancaiyang]

Qt 3D initially support obj modules without materials. Take a try.

[z69333186]

@jiancaiyang Thanks, I have found the Qt Documentation about the Qt 3D C++ Classes(https://doc.qt.io/qt-5/qt3d-cpp.html) and I know there is a AssimpIO Class(https://doc.qt.io/qt-5/qt3drender-assimpio.html), but i can't use it(I include <AssimpIO> but resulted in a "file not found" compiler error ) I don't whether QT don't support Assimp now or not. is there any way to load obj modules except AssimpIO Class?

[SGaist]

Which version of Qt are you using ?

Did you add QT += 3drender to your .pro file ? If so, did you re-run qmake after that ?

[guy incognito]

I did it this way in Qt3D:

1. Create a .qrc file as resource
2. add it to your .pro:

RESOURCES += \
          obj.qrc

2. content of .qrc file looks like this, make sure the .obj file is in the right directory:

<RCC>
    <qresource prefix="/">
        <file>object1.obj</file>
        <file>object2.obj</file>
    </qresource>
</RCC>

3. create a QEntity with all needed components like QTransform, QMaterial and especially QMesh
4. Add the .obj as source for the mesh:

    Qt3DRender::QMesh *mesh = new Qt3DRender::QMesh();
    mesh->setSource(QUrl(QStringLiteral("qrc:/object1.obj")));

5. Add mesh and other components to entity:

Qt3DCore::QEntity *object = new Qt3DCore::QEntity(rootEntity);
object->addComponent(mesh);

6. Finished

[z69333186]

Thanks for all the help.I have found to load the 3D model file(.obj) into Qt and control it.
Initially, I try to use C++ to complete all the function(display and control), but I find it a little complex for me. So I decide using QML to display the model and using C++ to control it.

I post the approach I used:

First, loading and displaying the 3D model using QML, you can refer to Qt 3D: Wireframe QML Example and Qt 3D: Scene3D QML Example. I think these two example include almost all the detail you need when loading and displaying the 3D model.

Second, i notice Entity has a property:Transform, which decide the position and angle of the 3D model displaying in the scene. The Transform accept scale, matrix, translation or rotation to define the property. So i define a C++ class, the class has some member variables that are QMatrix4x4 type. Obviously, I use QMatrix4x4 to store the coordinate matrix.

Third, I export the C ++ object into QML as a property that QML can use(refer to setContextProperty).

Fourth, bind property like this:
Transform {
id: transform
matrix: matrix.matrix
}

Fifth, when i want to change the position or angle, i just use C++ to change the QMatrix4x4 member variables, QML will update the scene automatically.

Finished~~~

[z69333186]

@guy-incognito Thank you for your help. Finally I use QML to display the 3D model and C++ to control it, but you still help me a lot. Thanks