Qt3D : How to display text on the 3D Window screen? - c++

Question

How does one display text on the 3D window screen? I know they a text2D entity module, but thats for displaying text in 3D next to the objects. I want to know if I can display 2D text on the screen.
Im using C++ so would like to know if this possible in C++ and not qml thanks.

Answer 1

There is QText2DEntity class for allowing the creation of a 2D text in 3D space.
#include <QApplication>
#include <QGuiApplication>
#include <Qt3DExtras>
#include <Qt3DRender/qcamera.h>
#include <Qt3DCore/qentity.h>
#include <Qt3DRender/qcameralens.h>
#include <QtWidgets/QWidget>
#include <QtWidgets/QHBoxLayout>
int main(int argc, char **argv)
{
QApplication a(argc, argv);
auto *view = new Qt3DExtras::Qt3DWindow;
view->defaultFrameGraph()->setClearColor(QColor(QRgb(0x4d4d4f)));
auto *container = QWidget::createWindowContainer(view);
auto screenSize = view->screen()->size();
container->setMinimumSize(QSize(200, 100));
container->setMaximumSize(screenSize);
auto *widget = new QWidget;
auto *hLayout = new QHBoxLayout(widget);
hLayout->addWidget(container, 1);
auto *input = new Qt3DInput::QInputAspect;
view->registerAspect(input);
// Root entity
auto *rootEntity = new Qt3DCore::QEntity();
// Camera
auto *cameraEntity = view->camera();
cameraEntity->lens()->setPerspectiveProjection(45.0f, 16.0f/7.0f, 0.1f, 1000.0f);
cameraEntity->setPosition(QVector3D(0, 10.0f, 20.0f));
cameraEntity->setUpVector(QVector3D(0, 1, 0));
cameraEntity->setViewCenter(QVector3D(0, 0, 0));
//light
auto *lightEntity = new Qt3DCore::QEntity(rootEntity);
auto *light = new Qt3DRender::QPointLight(lightEntity);
light->setColor("white");
light->setIntensity(1);
lightEntity->addComponent(light);
auto *lightTransform = new Qt3DCore::QTransform(lightEntity);
lightTransform->setTranslation(cameraEntity->position());
lightEntity->addComponent(lightTransform);
// For camera controls
auto *camController = new Qt3DExtras::QOrbitCameraController (rootEntity);
camController->setCamera(cameraEntity);
// Set root object of the scene
view->setRootEntity(rootEntity);
auto *text2dTransform = new Qt3DCore::QTransform;
text2dTransform->setScale(0.125f);
text2dTransform->setTranslation(QVector3D(-5, 0, 5));
auto *text2d = new Qt3DExtras::QText2DEntity(rootEntity);
text2d->setFont(QFont("monospace"));
text2d->setHeight(20);
text2d->setWidth(100);
text2d->setText("A");
text2d->setColor(Qt::yellow);
text2d->addComponent(text2dTransform);
widget->show();
widget->resize(1200, 800);
return a.exec();
}

Answer 2

Parisa has already provided a nice solution, I'll just post here mine here in case you are looking for something which allows to draw UI-like text:
Like stated in the comments, either draw a rectangular surface on top of everything using orthographic projection mode (similar to my Qt3DBackground example, just draw the texture last and make it transparent).
Or instead use my Qt3D Widget which allows to add Qt's widgets onto Qt3D. This way, you can draw your scene and use a simple QLabel on top.