[Interest] Qt3D : QSceneLoader - determining scene level geometry bounding box
Nicholas Yue
yue.nicholas at gmail.com
Wed Aug 3 01:14:56 CEST 2022
Thank you Mike.
Follow up question:
Given a
```
Qt3DRender::QSceneLoader *sceneLoader;
```
How do we get at this QGeometryRenderer object to be able to call the
impliciteMinPoint (), impliciteMaxPoint () properties ?
Cheers
On Tue, 2 Aug 2022 at 05:56, Mike Krus <mike.krus at kdab.com> wrote:
> Hi
>
> if you are using Qt6, then yes.
>
> For a specific object, QGeometryRenderer derives from QBoundingVolume
> which has impliciteMinPoint and impliciteMaxPoint properties.
>
> If you’re interested in the bounding volume of a portion of the scene
> graph, all a QBoundingVolume component at the root and the
> same properties will be updated.
>
> In Qt5, the QGeometry node associated with each render has similar min/max
> properties (note that they only valid if the mesh uses all the geometry).
>
> Hope this helps,
>
> Mike
>
>
> > On 1 Aug 2022, at 16:05, Nicholas Yue <yue.nicholas at gmail.com> wrote:
> >
> > Hi,
> >
> > I am diving into the geometry scene via QSceneLoader.
> >
> > Using the following code as a starting point, I wish to place the
> camera such that it automatically accommodates scenes of different sizes.
> >
> > One way I am thinking of doing is to base on the scene geometry
> bounding box.
> >
> > Is there a method or API which I can call to query the entire scene
> geometry bounding box ? Or do I have to walk the entire scene to build that
> up by querying the bounding box for every geometry in the scene ?
> >
> > Any sample code I can view to get me going ?
> >
> > ```
> >
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> ****************************************************************************/
> >
> > #include <QFileDialog>
> > #include <QApplication>
> >
> > #include <Qt3DRender/QCamera>
> > #include <Qt3DCore/QEntity>
> > #include <Qt3DCore/QAspectEngine>
> > #include <Qt3DInput/QInputAspect>
> > #include <Qt3DRender/QSceneLoader>
> > #include <Qt3DRender/QRenderAspect>
> > #include <Qt3DExtras/QForwardRenderer>
> > #include <Qt3DExtras/qt3dwindow.h>
> > // #include <Qt3DExtras/qfirstpersoncameracontroller.h>
> > #include "MyCameraController.h"
> > #include "TrackballCameraController.h"
> >
> > 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 ac, char **av)
> > {
> > QApplication app(ac, av);
> > Qt3DExtras::Qt3DWindow view;
> > view.defaultFrameGraph()->setClearColor(Qt::black);
> >
> > // Root entity
> > Qt3DCore::QEntity *sceneRoot = new Qt3DCore::QEntity();
> >
> > // Scene Camera
> > Qt3DRender::QCamera *camera = view.camera();
> >
> camera->setProjectionType(Qt3DRender::QCameraLens::PerspectiveProjection);
> > camera->setViewCenter(QVector3D(0.0f, 3.5f, 0.0f));
> > camera->setPosition(QVector3D(0.0f, 3.5f, 25.0f));
> > camera->setNearPlane(0.001f);
> > camera->setFarPlane(10000.0f);
> >
> > // For camera controls
> > // Qt3DExtras::QFirstPersonCameraController *camController = new
> Qt3DExtras::QFirstPersonCameraController(sceneRoot);
> > TrackballCameraController *camController = new
> TrackballCameraController(sceneRoot);
> > camController->setWindowSize(QSize(view.width(),view.height())); //
> https://github.com/cjmdaixi/Qt3DTrackball/issues/1#issuecomment-544183228
> > camController->setCamera(camera);
> >
> > // Scene loader
> > Qt3DCore::QEntity *sceneLoaderEntity = new
> Qt3DCore::QEntity(sceneRoot);
> > Qt3DRender::QSceneLoader *sceneLoader = new
> Qt3DRender::QSceneLoader(sceneLoaderEntity);
> > SceneWalker sceneWalker(sceneLoader);
> > QObject::connect(sceneLoader,
> &Qt3DRender::QSceneLoader::statusChanged, &sceneWalker,
> &SceneWalker::onStatusChanged);
> > sceneLoaderEntity->addComponent(sceneLoader);
> >
> > QStringList args = QCoreApplication::arguments();
> > QUrl sourceFileName;
> > if (args.count() <= 1) {
> > QWidget *container = new QWidget();
> > QFileDialog dialog;
> > dialog.setFileMode(QFileDialog::AnyFile);
> > sourceFileName = dialog.getOpenFileUrl(container,
> QStringLiteral("Open a scene file"));
> > } else {
> > sourceFileName = QUrl::fromLocalFile(args[1]);
> > }
> >
> > if (sourceFileName.isEmpty())
> > return 0;
> >
> > sceneLoader->setSource(sourceFileName);
> >
> > view.setRootEntity(sceneRoot);
> > view.show();
> >
> > return app.exec();
> > }
> > ```
> >
> > Cheers
> > --
> > Nicholas Yue
> > https://www.linkedin.com/in/nicholasyue/
> > _______________________________________________
> > Interest mailing list
> > Interest at qt-project.org
> > https://lists.qt-project.org/listinfo/interest
>
> —
> Mike Krus | mike.krus at kdab.com | Senior Software Engineer & Teamlead
> KDAB (UK) Ltd., a KDAB Group company
> Tel: UK Office +44 1625 809908 Mobile +44 7833 491941
> KDAB - The Qt Experts, C++, OpenGL Experts
>
>
>
--
Nicholas Yue
https://www.linkedin.com/in/nicholasyue/
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