Qt3D picking triangles

Reply to Qt3D picking triangles on Mon, 29 Oct 2018 08:36:29 GMT

m3g1dd — Mon, 29 Oct 2018 08:36:29 GMT

@unclejimbo-0 Hello. My Entity is imported with Qt3DRender::QSceneLoader like this:

m_sceneLoaderEntity = new Qt3DCore::QEntity();

 Qt3DRender::QSceneLoader *sceneLoader = new Qt3DRender::QSceneLoader(m_sceneLoaderEntity);

// EditorSceneItemModel::handleImportEntityLoaderStatusChanged is a slot developed to react to a signal when import operation is finished
QObject::connect(sceneLoader, &Qt3DRender::QSceneLoader::statusChanged,
                     this, &EditorSceneItemModel::handleImportEntityLoaderStatusChanged);

sceneLoader->setSource(fileUrl);

m_sceneLoaderEntity->addComponent(sceneLoader);

So, it might be considered as custom mesh! I think picking triangles should work fine with custom meshes. By the way, I'm working with Qt 5.11.2

Reply to Qt3D picking triangles on Thu, 25 Oct 2018 15:05:25 GMT

unclejimbo 0 — Thu, 25 Oct 2018 15:05:25 GMT

@m3g1dd Hi, is your QGeometryRenderer component a built-in mesh in Qt3SDExtras or is it a custom mesh?

I've got some troubles picking triangles for a custom mesh built from QGeometry, QAttribute and QBuffer. The clicked event never trigers. But when I use a built-in mesh like QSphereMesh it works fine. Any idea how to do triangle picking for custom meshes?

Reply to Qt3D picking triangles on Thu, 25 Oct 2018 10:46:25 GMT

m3g1dd — Thu, 25 Oct 2018 10:46:25 GMT

@RLayman I had the same problem, I had this method to add Qt3DRender::QObjectPicker to my entities:

Qt3DRender::QObjectPicker *EditorScene::createObjectPickerForEntity(Qt3DCore::QEntity *entity)
{
    Qt3DRender::QObjectPicker *picker = new Qt3DRender::QObjectPicker(entity);
    entity->addComponent(picker);
    connect(picker, &Qt3DRender::QObjectPicker::pressed, this, &EditorScene::handlePickerPress);
return picker;
}

My rendering settings Qt3DRender::QRenderSettings are added to entities like this, note that the PickMethod must be TrianglePicking:

m_renderSettings = new Qt3DRender::QRenderSettings();
    m_renderSettings->pickingSettings()->setPickMethod(Qt3DRender::QPickingSettings::TrianglePicking);
    m_renderSettings->pickingSettings()->setPickResultMode(Qt3DRender::QPickingSettings::NearestPick);

entity->addComponent(m_renderSettings);

And I had this code to handle click press events I was able to print click position/location by event->worldIntersection() but i didn't know how to get the index of clicked triangle. Finally, I managed to print the index of clicked triangle by casting Qt3DRender::QPickEvent * as Qt3DRender::QPickTriangleEvent *:

void EditorScene::handlePickerPress(Qt3DRender::QPickEvent *event)
{
    // // "event" will give me clicked coordinates like this:
    qDebug() << __func__ << ": global Coord: " << event->worldIntersection();
    
    // // Also I can get picked/clicked triangle index and its vertices by casting event pointer type:
    Qt3DRender::QPickTriangleEvent *eventTri = static_cast(event);
    qDebug() << __func__ << "Pick Triangle Index: " << eventTri->triangleIndex();
    qDebug() << __func__ << "Pick Triangle Vertex 1: " << eventTri->vertex1Index();
    qDebug() << __func__ << "Pick Triangle Vertex 2: " << eventTri->vertex2Index();
    qDebug() << __func__ << "Pick Triangle Vertex 3: " << eventTri->vertex3Index();
}