How to zoom toward a 3D mesh with qt? - c++

Question

I'm using a Wheelevent to Zoom in/out in a QWidget view,in use the event to translate the QCamera, is there a solution from the qt api to move toward a point or zoom with the camera to a specific point? I searched in many sections but did'nt find something useful unfortunately.

Answer 1

Edit: Stefan Reinhardt suggested to use QAbstractCameraController to achieve what you want to do. The example I provided is a quick-and-dirty solution. I agree that using the camera controller is the way intended in Qt3D.
The Qt3D API doesn't support this directly, but you can implement it easily yourself.
Here is a minimally working example, that should get you started (note, that you have to adjust the upvector, when scrolling past the view center I guess):
main.cpp:
#include <QApplication>
#include "graphicswindow.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
GraphicsWindow graphicsWindow;
graphicsWindow.show();
return a.exec();
}
graphicswindow.h:
#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DCore/QEntity>
class GraphicsWindow : public Qt3DExtras::Qt3DWindow {
public:
GraphicsWindow();
void wheelEvent ( QWheelEvent * event ) override;
private:
Qt3DCore::QEntity *createScene();
};
graphicswindow.cpp:
#include "graphicswindow.h"
#include <QMouseEvent>
#include <QVector3D>
#include <Qt3DRender/QCamera>
#include <Qt3DRender/QMaterial>
#include <Qt3DExtras/QGoochMaterial>
#include <Qt3DExtras/QCuboidMesh>
GraphicsWindow::GraphicsWindow() : Qt3DExtras::Qt3DWindow() {
// You could also create a dedicated setup method
Qt3DCore::QEntity *root = createScene();
setRootEntity(root);
Qt3DRender::QCamera *camera = this->camera();
camera->lens()->setPerspectiveProjection(45.0f, 16.0f/9.0f, 0.1f, 1000.0f);
camera->setPosition(QVector3D(20.0, 20.0, 20.0f));
camera->setViewCenter(QVector3D(0, 0, 0));
}
void GraphicsWindow::wheelEvent(QWheelEvent *event) {
QVector3D camPos = this->camera()->position();
camPos.normalize();
camPos = this->camera()->position() - QVector3D(event->delta() / 300.f,
event->delta() / 300.f,
event->delta() / 300.f);
this->camera()->setPosition(camPos);
}
Qt3DCore::QEntity* GraphicsWindow::createScene() {
Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity;
Qt3DRender::QMaterial *material = new Qt3DExtras::QGoochMaterial(rootEntity);
//Cube
Qt3DCore::QEntity *cubeEntity = new Qt3DCore::QEntity(rootEntity);
Qt3DExtras::QCuboidMesh *cubeMesh = new Qt3DExtras::QCuboidMesh;
cubeEntity->addComponent(cubeMesh);
cubeEntity->addComponent(material);
return rootEntity;
}