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I'm trying to create a Qt3D prototype which is able to render an obj which contains transparent objects. Therefor I need to somehow incorporate QSortPolicy with a custom frame graph. I put together a few examples which I found on the internet (unfortunately there aren't many Qt3D C++ examples). The source of the protoype is shown below. The problem is that I add a QTorusMesh and the content of the QSceneLoader to the root entity, but when rendered only the torus will be shown, the obj (in this case the monkey) is not rendered and I don't know why and also not how to debug it. I dumped all the trees (scene graph and frame graph) and couldn't find any inconsistency. Only thing I can think of that the loaded object somehow needs a different renderer (QGeometryRenderer) which needs to be added to the frame graph? Does someone know what I'm doing wrong?

Examples: Custom frame graph, Scene walker

#include <QGuiApplication>

#include <Qt3DCore/QEntity>
#include <Qt3DCore/QTransform>
#include <Qt3DCore/QAspectEngine>

#include <Qt3DInput/QInputAspect>

#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DExtras/QPhongMaterial>
#include <Qt3DExtras/QOrbitCameraController>
#include <Qt3DExtras/QTorusMesh>

#include <Qt3DRender/QCamera>
#include <Qt3DRender/QRenderAspect>
#include <Qt3DRender/QSceneLoader>
#include <Qt3DRender/QRenderSurfaceSelector>
#include <Qt3DRender/QClearBuffers>
#include <Qt3DRender/QLayerFilter>
#include <Qt3DRender/QViewport>
#include <Qt3DRender/QCameraSelector>
#include <Qt3DRender/QLayer>
#include <Qt3DRender/QRenderSettings>

class SceneWalker : public QObject

public:
 SceneWalker(Qt3DRender::QSceneLoader* loader):
 m_loader(loader)
 

 void onStatusChanged();

private:
 void walkEntity(Qt3DCore::QEntity* e, int depth = 0);

 Qt3DRender::QSceneLoader* m_loader;
;

void SceneWalker::onStatusChanged()

 qDebug() << "Status changed:" << m_loader->status();
 if (m_loader->status() != Qt3DRender::QSceneLoader::Ready)
 return;

 // The QSceneLoader instance is a component of an entity. The loaded scene
 // tree is added under this entity.
 QVector<Qt3DCore::QEntity*> entities = m_loader->entities();

 // Technically there could be multiple entities referencing the scene loader
 // but sharing is discouraged, and in our case there will be one anyhow.
 if (entities.isEmpty())
 return;

 Qt3DCore::QEntity* root = entities[0];
 // Print the tree.
 walkEntity(root);

 // To access a given node (like a named mesh in the scene), use QObject::findChild().
 // The scene structure and names always depend on the asset.
 Qt3DCore::QEntity* e = root->findChild<Qt3DCore::QEntity*>(QStringLiteral("PlanePropeller_mesh")); // toyplane.obj
 if (e)
 qDebug() << "Found propeller node" << e << "with components" << e->components();


void SceneWalker::walkEntity(Qt3DCore::QEntity* e, int depth)

 Qt3DCore::QNodeVector nodes = e->childNodes();
 for (int i = 0; i < nodes.count(); ++i)
 
 Qt3DCore::QNode* node = nodes[i];
 Qt3DCore::QEntity* entity = qobject_cast<Qt3DCore::QEntity*>(node);
 if (entity)
 
 QString indent;
 indent.fill(' ', depth * 2);
 qDebug().noquote() << indent << "Entity:" << entity << "Components:" << entity->components();
 walkEntity(entity, depth + 1);
 
 


int main(int argc, char* argv)

 QGuiApplication app(argc, argv);

 Qt3DExtras::Qt3DWindow* window = new Qt3DExtras::Qt3DWindow();

 // Root
 Qt3DCore::QEntity* rootEntity = new Qt3DCore::QEntity();
 window->setRootEntity(rootEntity);

 Qt3DRender::QRenderSurfaceSelector *renderSurfaceSelector = new Qt3DRender::QRenderSurfaceSelector();
 renderSurfaceSelector->setSurface(window);

 // clearing the buffers
 Qt3DRender::QClearBuffers* clearBuffers = new Qt3DRender::QClearBuffers(renderSurfaceSelector);
 clearBuffers->setBuffers(Qt3DRender::QClearBuffers::ColorDepthBuffer);

 // Framegraph for objects
 Qt3DRender::QLayerFilter* objectsLayerFilter = new Qt3DRender::QLayerFilter(renderSurfaceSelector);
 Qt3DRender::QLayer* objectsLayer = new Qt3DRender::QLayer(objectsLayerFilter);
 objectsLayerFilter->addLayer(objectsLayer);
 Qt3DRender::QViewport* viewport = new Qt3DRender::QViewport(objectsLayer);
 Qt3DRender::QCameraSelector* objectsCameraSelector = new Qt3DRender::QCameraSelector(viewport);
 Qt3DRender::QCamera* objectsCamera = new Qt3DRender::QCamera(objectsCameraSelector);
 objectsCamera->lens()->setPerspectiveProjection(45.f, 16.0f/9.0f, 0.01f, 1000.f);
 objectsCamera->setPosition(QVector3D(0, 0, -10));
 objectsCamera->setViewCenter(QVector3D(0, 0, 0));
 objectsCamera->setUpVector(QVector3D(0, 1, 0));
 objectsCameraSelector->setCamera(objectsCamera);

 // Set the new framegraph
 window->setActiveFrameGraph(renderSurfaceSelector);
 window->renderSettings()->setRenderPolicy(Qt3DRender::QRenderSettings::Always);

 // camera controls
 Qt3DExtras::QOrbitCameraController* camController = new Qt3DExtras::QOrbitCameraController(rootEntity);
 camController->setLinearSpeed(50.0f);
 camController->setLookSpeed(180.0f);
 camController->setCamera(objectsCamera);

 // Torus
 Qt3DCore::QEntity* torusEntity = new Qt3DCore::QEntity(rootEntity);
 Qt3DExtras::QTorusMesh* torusMesh = new Qt3DExtras::QTorusMesh(torusEntity);
 torusMesh->setSlices(50.0f);
 torusMesh->setRings(50.0f);
 torusMesh->setRadius(2.0f);
 Qt3DExtras::QPhongMaterial* torusMaterial = new Qt3DExtras::QPhongMaterial(torusEntity);
 torusMaterial->setAmbient(Qt::gray);
 Qt3DCore::QTransform* torusTransform = new Qt3DCore::QTransform(torusEntity);
 torusTransform->setTranslation(QVector3D(0.0f, 0.0f, 10.0f));
 torusTransform->setRotationY(50.0f);
 torusTransform->setScale(2.0f);
 torusEntity->addComponent(torusTransform);
 torusEntity->addComponent(torusMesh);
 torusEntity->addComponent(torusMaterial);
 torusEntity->addComponent(objectsLayer);

 // Scene loader
 Qt3DCore::QEntity* sceneLoaderEntity = new Qt3DCore::QEntity(rootEntity);
 Qt3DRender::QSceneLoader* sceneLoader = new Qt3DRender::QSceneLoader(sceneLoaderEntity);
 sceneLoader->setSource(QUrl::fromLocalFile("monkey.obj"));

 // Transform
 Qt3DCore::QTransform* sceneLoaderTransform = new Qt3DCore::QTransform(sceneLoaderEntity);
 sceneLoaderTransform->setScale(2.0f);
 sceneLoaderTransform->setTranslation(QVector3D(0.0f, 0.0f, 10.0f));

 SceneWalker sceneWalker(sceneLoader);
 QObject::connect(sceneLoader, &Qt3DRender::QSceneLoader::statusChanged, &sceneWalker, &SceneWalker::onStatusChanged);

 sceneLoaderEntity->addComponent(sceneLoader);
 sceneLoaderEntity->addComponent(sceneLoaderTransform);
 sceneLoaderEntity->addComponent(objectsLayer);

 window->show();

 return app.exec();