How to render in Qt3D in standard GUI application?

Question

I enjoy using Qt3D, but all of the examples I see for it are full window applications. What I can't understand from the examples is how to add a qt3d rendering window to a regular qt gui application.

Basically what I want is a little rendering widget for my Qt5 Gui application.

I've looked into Qtgl widget, but I really want to use the scene management abilities of Qt3D.

How can I render as a sub window inside of a qt Gui window?

Is this possible?

Update

So I added this to my MainWindow.cpp It is loosely based off of this https://www.qt.io/blog/2013/02/19/introducing-qwidgetcreatewindowcontainer

LoadModelView *view = new LoadModelView(); //Crashes on this. Will not compile with
                                           // LoadModelView(this) 

    QWidget *container = QWidget::createWindowContainer(view);
    container->setFocusPolicy(Qt::TabFocus);

    ui->gridLayout->addWidget(container);

which seems right.

my load_model.cpp begins like this:

#include "qglmaterialcollection.h"
#include "qglmaterial.h"
#include "qglscenenode.h"
#include "qgllightmodel.h"
#include "qglabstractscene.h"
#include <QtGui/qmatrix4x4.h>

#include <QPropertyAnimation>
#include <QtCore/qmath.h>

#define DEGREE_TO_RAD (3.1415926/180.0)

LoadModelView::LoadModelView(QWindow *parent)
    : QGLView(parent)
    , m_pSTLScene(0)
{
    loadModels();

    camera()->setCenter(QVector3D(0, 0, 0));
    camera()->setEye(QVector3D(0, 4, 10));
}
LoadModelView::~LoadModelView()
{
    delete m_pSTLScene;
}

void LoadModelView::paintGL(QGLPainter *painter)
{
    QMatrix4x4 stlWorld;
    stlWorld.setToIdentity();
    stlWorld.scale(0.1);
    stlWorld.translate(QVector3D(2.0,0.0,0.0));

    painter->setStandardEffect(QGL::LitMaterial);
    painter->setFaceColor(QGL::AllFaces,QColor(170,202,0));

    painter->modelViewMatrix() = camera()->modelViewMatrix() * stlWorld;

    m_pSTLScene->mainNode()->draw(painter);
}

void FixNodesRecursive(int matIndex, QGLSceneNode* pNode)
{
    if (pNode) {
        pNode->setMaterialIndex(matIndex);
       // pNode->setEffect(QGL::FlatReplaceTexture2D);
        foreach (QGLSceneNode* pCh, pNode->children()) {
            FixNodesRecursive(matIndex, pCh);
        }
    }
}

void LoadModelView::loadModels()
{
    {
        m_pSTLScene = QGLAbstractScene::loadScene(QLatin1String(":/models/Sheep.stl"), QString(),"CorrectNormals CorrectAcute");
        Q_ASSERT(m_pSTLScene!=0);
        QGLMaterial *mat = new QGLMaterial;
        mat->setAmbientColor(QColor(170,202,0));
        mat->setDiffuseColor(QColor(170,202,0));
        mat->setShininess(128);

        QGLSceneNode* pSTLSceneRoot = m_pSTLScene->mainNode();
        int matIndex = pSTLSceneRoot->palette()->addMaterial(mat);
        pSTLSceneRoot->setMaterialIndex(matIndex);
        pSTLSceneRoot->setEffect(QGL::FlatReplaceTexture2D);
        FixNodesRecursive(matIndex,pSTLSceneRoot);
    }
}

It crashes with:

This application has requested the runtime to terminate it in an unusual way.

And in the qt application output:

Invalid parameter passed to C runtime function.

EDIT Added the rest of the class in question

I notice that in the example I am adapting https://github.com/Distrotech/qt3d/blob/master/tutorials/qt3d/penguin/main.cpp the window is initialized by saying:

LoadModelView view;

However, saying

LoadModelView *view = new LoadModelView(this)

crashes

Answer 1

You can subclass QGLView class which extends QGLWidget with support for 3D viewing:

class GLView : public QGLView
{
    Q_OBJECT

public:
    GLView(QWidget *parent = 0);
    ~GLView();

protected:
    void initializeGL(QGLPainter *painter);
    void paintGL(QGLPainter *painter);

private:
    QGLAbstractScene *m_scene;
    QGLSceneNode *m_rootNode;
};

GLView::GLView(QWidget *parent)
    : QGLView(parent)
    , m_scene(0)
    , m_rootNode(0)
{
    // Viewing Volume
    camera()->setFieldOfView(25);
    camera()->setNearPlane(1);
    camera()->setFarPlane(1000);

    // Position of the camera
    camera()->setEye(QVector3D(0, 3, 4));

    // Direction that the camera is pointing
    camera()->setCenter(QVector3D(0, 3, 0));
}

GLView::~GLView()
{
    delete m_scene;
}

void GLView::initializeGL(QGLPainter *painter)
{
    // Background color
    painter->setClearColor(QColor(70, 70, 70));

    // Load the 3d model from the file
    m_scene = QGLAbstractScene::loadScene("models/model1/simplemodel.obj");

    m_rootNode = m_scene->mainNode();
}

void GLView::paintGL(QGLPainter *painter)
{
    m_rootNode->draw(painter);
}

Qt 5.1 introduces the function QWidget::createWindowContainer(). A function that creates a QWidget wrapper for an existing QWindow, allowing it to live inside a QWidget-based application. You can use QWidget::createWindowContainer which creates a QWindow in a QWidget. This allows placing QWindow-subclasses in Widget-Layouts. This way you can embed your QGLView inside a widget.

Answer 2

This is how I did it on Qt5.10. This example shows a scene with a cuboid. Scene you can than use like a button or so... To use this add QT += 3dextras to your project file.

szene.h

#ifndef SCENE_H
#define SCENE_H

#include <QObject>
#include <QWidget>

class Scene
      : public QWidget
{
    Q_OBJECT

private:
    QWidget *container;

public:
    explicit Scene(QWidget *parent = nullptr);

protected:
    // reimplementation needed to handle resize events
    // http://doc.qt.io/qt-5/qwidget.html#resizeEvent
    void
    resizeEvent ( QResizeEvent * event );

public slots:
    void
    resizeView(QSize size);
};

#endif // SCENE_H

scene.cpp

#include "scene.h"

#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DExtras/QForwardRenderer>
#include <QQuaternion>
#include <Qt3DCore/QEntity>
#include <Qt3DCore/QTransform>
#include <Qt3DRender/QCamera>
#include <Qt3DExtras/QCuboidMesh>
#include <Qt3DExtras/QPhongMaterial>

Scene::Scene(QWidget *parent)
   : QWidget(parent)
{
    auto view = new Qt3DExtras::Qt3DWindow();

    // create a container for Qt3DWindow
    container = createWindowContainer(view,this);

    // background color
    view->defaultFrameGraph()->setClearColor(QColor(QRgb(0x575757)));

    // Root entity
    auto rootEntity = new Qt3DCore::QEntity();

    // Camera
    auto camera = new Camera(rootEntity,view);
    auto cameraEntity = view->camera();

    cameraEntity->setPosition(QVector3D(0, 0, 50.0f));
    cameraEntity->setUpVector(QVector3D(0, 1, 0));
    cameraEntity->setViewCenter(QVector3D(0, 0, 0));

    // Cuboid
    auto cuboidMesh = new Qt3DExtras::QCuboidMesh();

    // CuboidMesh Transform
    auto cuboidTransform = new Qt3DCore::QTransform();
    cuboidTransform->setScale(10.0f);
    cuboidTransform->setTranslation(QVector3D(0.0f, 0.0f, 0.0f));
    cuboidTransform->setRotation(QQuaternion(1,1.5,1,0).normalized());

    auto cuboidMaterial = new Qt3DExtras::QPhongMaterial();
    cuboidMaterial->setDiffuse(QColor(QRgb(0x005FFF)));

    // assamble entity
    auto cuboidEntity = new Qt3DCore::QEntity(rootEntity);
    cuboidEntity->addComponent(cuboidMesh);
    cuboidEntity->addComponent(cuboidMaterial);
    cuboidEntity->addComponent(cuboidTransform);

    // Set root object of the scene
    view->setRootEntity(rootEntity);
}

void
Scene::resizeView(QSize size)
{
    container->resize(size);
}

void
Scene::resizeEvent ( QResizeEvent * /*event*/ )
{
  resizeView(this->size());
}