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:

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

RESOURCES += \
          obj.qrc

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>

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

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

Add mesh and other components to entity:

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

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