Qt3D high CPU usage. No hardware acceleration?

Question

I just recently started to use QT3D for a sideproject at work. And i'm surprised how fast you get something that looks pretty decent (at least for my case).

But i still have an issue with rendering speed and CPU usage. I've written a small test program to showcase this (see below). As we use Ubuntu i though it may be an issue with the NVIDIA driver but i tested it at home on my Windows PC as well.

And had the same results:

• CPU usage is very high - 100% on one Core all the time.
• GPU usage show no real difference if the application is running or not.

So my best guess is that it uses software rendering instead of the hardware? Any ideas?

The example just draws 2000 Cuboids with random sizes on random positions with a light source above.

#include <QGuiApplication>
#include <QRandomGenerator>
#include <QHBoxLayout>

#include <Qt3DRender/QCamera>
#include <Qt3DCore/QEntity>

#include <QtWidgets/QApplication>
#include <QtWidgets/QWidget>
#include <QtGui/QScreen>

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

#include <Qt3DExtras/QForwardRenderer>
#include <Qt3DRender/QPointLight>
#include <Qt3DExtras/QCuboidMesh>
#include <Qt3DExtras/QDiffuseSpecularMaterial>

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

int main(int argc, char **argv)
{
    //basic window/widget stuff
    QApplication app(argc, argv);
    Qt3DExtras::Qt3DWindow *view = new Qt3DExtras::Qt3DWindow();
    view->defaultFrameGraph()->setClearColor(QColor(QRgb(0x4d4d4f)));
    QWidget *container = QWidget::createWindowContainer(view);
    QSize screenSize = view->screen()->size();
    container->setMinimumSize(QSize(200, 100));
    container->setMaximumSize(screenSize);
    QWidget *widget = new QWidget;
    QHBoxLayout *hLayout = new QHBoxLayout(widget);
    hLayout->addWidget(container, 1);

    //root entity
    Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity();
    view->setRootEntity(rootEntity);

    //setup camera
    view->camera()->lens()->setPerspectiveProjection(45.0f, 16.0f/9.0f, 10.0f, 5000.0f);
    view->camera()->setPosition(QVector3D(0, 0, 3000));
    view->camera()->setUpVector(QVector3D(0, 1, 0));
    view->camera()->setViewCenter(QVector3D(0, 0, 0));

    //orbit camera controller
    Qt3DExtras::QOrbitCameraController *camController = new Qt3DExtras::QOrbitCameraController(rootEntity);
    camController->setCamera(view->camera());
    camController->setLookSpeed(500);

    //add light
    Qt3DCore::QEntity *lightEntity = new Qt3DCore::QEntity(rootEntity);
    Qt3DRender::QPointLight *light = new Qt3DRender::QPointLight(lightEntity);
    light->setColor("white");
    light->setIntensity(1);
    lightEntity->addComponent(light);
    Qt3DCore::QTransform *lightTransform = new Qt3DCore::QTransform(lightEntity);
    lightTransform->setTranslation(QVector3D(0, 5000, 0));
    lightEntity->addComponent(lightTransform);

    //add objects
    QRandomGenerator rng(1234);
    for(int i = 0; i <= 2000; i++)
    {
        Qt3DCore::QEntity* shapeEntity = new Qt3DCore::QEntity(rootEntity);
        Qt3DExtras::QCuboidMesh* mesh = new Qt3DExtras::QCuboidMesh();
        mesh->setXExtent(int(rng.generate() % 30)+20);
        mesh->setYExtent(int(rng.generate() % 30)+20);
        mesh->setZExtent(int(rng.generate() % 30)+20);
        shapeEntity->addComponent(mesh);
        Qt3DExtras::QDiffuseSpecularMaterial *material = new Qt3DExtras::QDiffuseSpecularMaterial();
        material->setAmbient(QColor(Qt::red).darker(150));
        material->setDiffuse(QColor(Qt::red));

        shapeEntity->addComponent(material);
        Qt3DCore::QTransform* pTrans = new Qt3DCore::QTransform();
        pTrans->setTranslation(QVector3D(int(rng.generate() % 2000)-1000, int(rng.generate() % 2000)-1000, int(rng.generate() % 2000)-1000));
        shapeEntity->addComponent(pTrans);
    }

    //show
    widget->show();
    widget->resize(1200, 800);

    return app.exec();
}