qgschunkedentity.cpp

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/***************************************************************************
  qgschunkedentity.cpp
  --------------------------------------
  Date                 : July 2017
  Copyright            : (C) 2017 by Martin Dobias
  Email                : wonder dot sk at gmail dot com
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#include "qgschunkedentity.h"
 
#include "qgs3dmapsettings.h"
#include "qgs3dutils.h"
#include "qgschunkboundsentity_p.h"
#include "qgschunklist_p.h"
#include "qgschunkloader.h"
#include "qgschunknode.h"
#include "qgseventtracing.h"
#include "qgsgeotransform.h"
#include "qgsmaplayer.h"
 
#include <QElapsedTimer>
#include <QString>
#include <QVector4D>
#include <queue>
 
#include "moc_qgschunkedentity.cpp"
 
using namespace Qt::StringLiterals;

 
static float screenSpaceError( const QgsAABB &nodeBbox, float nodeError, const QgsChunkedEntity::SceneContext &sceneContext )
{
  if ( nodeError <= 0 ) //it happens for meshes
    return 0;
 
  float dist = nodeBbox.distanceFromPoint( sceneContext.cameraPos );
 
  // TODO: what to do when distance == 0 ?
 
  float sse = Qgs3DUtils::screenSpaceError( nodeError, dist, sceneContext.screenSizePx, sceneContext.cameraFov );
  return sse;
}
 
 
static bool hasAnyActiveChildren( QgsChunkNode *node, QList<QgsChunkNode *> &activeNodes )
{
  for ( int i = 0; i < node->childCount(); ++i )
  {
    QgsChunkNode *child = node->children()[i];
    if ( child->entity() && activeNodes.contains( child ) )
      return true;
    if ( hasAnyActiveChildren( child, activeNodes ) )
      return true;
  }
  return false;
}
 
static void addTileTraceEvent( QObject &self, QgsChunkNode &node, QgsEventTracing::EventType eventType, QString name )
{
  QgsEventTracing::addEvent( eventType, u"3D"_s, name + u" "_s + node.tileId().text(), u"%1 %2"_s.arg( self.objectName(), node.tileId().text() ) );
}
 
QgsChunkedEntity::QgsChunkedEntity( Qgs3DMapSettings *mapSettings, float tau, QgsChunkLoaderFactory *loaderFactory, bool ownsFactory, int primitiveBudget, Qt3DCore::QNode *parent )
  : Qgs3DMapSceneEntity( mapSettings, parent )
  , mTau( tau )
  , mChunkLoaderFactory( loaderFactory )
  , mOwnsFactory( ownsFactory )
  , mPrimitivesBudget( primitiveBudget )
{
  mRootNode.reset( loaderFactory->createRootNode() );
  mChunkLoaderQueue = std::make_unique<QgsChunkList>();
  mReplacementQueue = std::make_unique<QgsChunkList>();
 
  // in case the chunk loader factory supports fetching of hierarchy in background (to avoid GUI freezes)
  connect( loaderFactory, &QgsChunkLoaderFactory::childrenPrepared, this, [this] {
    setNeedsUpdate( true );
    emit pendingJobsCountChanged();
  } );
}
 
 
QgsChunkedEntity::~QgsChunkedEntity()
{
  // derived classes have to make sure that any pending active job has finished / been canceled
  // before getting to this destructor - here it would be too late to cancel them
  // (e.g. objects required for loading/updating have been deleted already)
  Q_ASSERT( mActiveJobs.isEmpty() );
 
  // clean up any pending load requests
  while ( !mChunkLoaderQueue->isEmpty() )
  {
    QgsChunkListEntry *entry = mChunkLoaderQueue->takeFirst();
    QgsChunkNode *node = entry->chunk;
 
    if ( node->state() == QgsChunkNode::QueuedForLoad )
      node->cancelQueuedForLoad();
    else if ( node->state() == QgsChunkNode::QueuedForUpdate )
      node->cancelQueuedForUpdate();
    else
      Q_ASSERT( false ); // impossible!
  }
 
  while ( !mReplacementQueue->isEmpty() )
  {
    QgsChunkListEntry *entry = mReplacementQueue->takeFirst();
 
    // remove loaded data from node
    entry->chunk->unloadChunk(); // also deletes the entry
  }
 
  if ( mOwnsFactory )
  {
    delete mChunkLoaderFactory;
  }
}
 
 
void QgsChunkedEntity::handleSceneUpdate( const SceneContext &sceneContext )
{
  if ( !mIsValid )
    return;
 
  // Let's start the update by removing from loader queue chunks that
  // would get frustum culled if loaded (outside of the current view
  // of the camera). Removing them keeps the loading queue shorter,
  // and we avoid loading chunks that we only wanted for a short period
  // of time when camera was moving.
  pruneLoaderQueue( sceneContext );
 
  QElapsedTimer t;
  t.start();
 
  int oldJobsCount = pendingJobsCount();
 
  QSet<QgsChunkNode *> activeBefore = qgis::listToSet( mActiveNodes );
  mActiveNodes.clear();
  mFrustumCulled = 0;
  mCurrentTime = QTime::currentTime();
 
  update( mRootNode.get(), sceneContext );
 
#ifdef QGISDEBUG
  int enabled = 0, disabled = 0, unloaded = 0;
#endif
 
  for ( QgsChunkNode *node : std::as_const( mActiveNodes ) )
  {
    if ( activeBefore.contains( node ) )
    {
      activeBefore.remove( node );
    }
    else
    {
      if ( !node->entity() )
      {
        QgsDebugError( "Active node has null entity - this should never happen!" );
        continue;
      }
      node->entity()->setEnabled( true );
 
      // let's make sure that any entity we're about to show has the right scene origin set
      const QList<QgsGeoTransform *> transforms = node->entity()->findChildren<QgsGeoTransform *>();
      for ( QgsGeoTransform *transform : transforms )
      {
        transform->setOrigin( mMapSettings->origin() );
      }
 
#ifdef QGISDEBUG
      ++enabled;
#endif
    }
  }
 
  // disable those that were active but will not be anymore
  for ( QgsChunkNode *node : activeBefore )
  {
    if ( !node->entity() )
    {
      QgsDebugError( "Active node has null entity - this should never happen!" );
      continue;
    }
    node->entity()->setEnabled( false );
#ifdef QGISDEBUG
    ++disabled;
#endif
  }
 
  // if this entity's loaded nodes are using more GPU memory than allowed,
  // let's try to unload those that are not needed right now
#ifdef QGISDEBUG
  unloaded = unloadNodes();
#else
  unloadNodes();
#endif
 
  if ( mBboxesEntity )
  {
    QList<QgsBox3D> bboxes;
    for ( QgsChunkNode *n : std::as_const( mActiveNodes ) )
      bboxes << n->box3D();
    mBboxesEntity->setBoxes( bboxes );
  }
 
  // start a job from queue if there is anything waiting
  startJobs();
 
  mNeedsUpdate = false; // just updated
 
  if ( pendingJobsCount() != oldJobsCount )
    emit pendingJobsCountChanged();
 
#ifdef QGISDEBUG
  QgsDebugMsgLevel(
    u"update: active %1 enabled %2 disabled %3 | culled %4 | loading %5 loaded %6 | unloaded %7 elapsed %8ms"_s.arg( mActiveNodes.count() )
      .arg( enabled )
      .arg( disabled )
      .arg( mFrustumCulled )
      .arg( mChunkLoaderQueue->count() )
      .arg( mReplacementQueue->count() )
      .arg( unloaded )
      .arg( t.elapsed() ),
    2
  );
#endif
}
 
 
int QgsChunkedEntity::unloadNodes()
{
  double usedGpuMemory = Qgs3DUtils::calculateEntityGpuMemorySize( this );
  if ( usedGpuMemory <= mGpuMemoryLimit )
  {
    setHasReachedGpuMemoryLimit( false );
    return 0;
  }
 
  QgsDebugMsgLevel( u"Going to unload nodes to free GPU memory (used: %1 MB, limit: %2 MB)"_s.arg( usedGpuMemory ).arg( mGpuMemoryLimit ), 2 );
 
  int unloaded = 0;
 
  // unload nodes starting from the back of the queue with currently loaded
  // nodes - i.e. those that have been least recently used
  QgsChunkListEntry *entry = mReplacementQueue->last();
  while ( entry && usedGpuMemory > mGpuMemoryLimit )
  {
    // not all nodes are safe to unload: we do not want to unload nodes
    // that are currently active, or have their descendants active or their
    // siblings or their descendants are active (because in the next scene
    // update, these would be very likely loaded again, making the unload worthless)
    if ( entry->chunk->parent() && !hasAnyActiveChildren( entry->chunk->parent(), mActiveNodes ) )
    {
      QgsChunkListEntry *entryPrev = entry->prev;
      mReplacementQueue->takeEntry( entry );
      usedGpuMemory -= Qgs3DUtils::calculateEntityGpuMemorySize( entry->chunk->entity() );
      mActiveNodes.removeOne( entry->chunk );
      entry->chunk->unloadChunk(); // also deletes the entry
      ++unloaded;
      entry = entryPrev;
    }
    else
    {
      entry = entry->prev;
    }
  }
 
  if ( usedGpuMemory > mGpuMemoryLimit )
  {
    setHasReachedGpuMemoryLimit( true );
    QgsDebugMsgLevel( u"Unable to unload enough nodes to free GPU memory (used: %1 MB, limit: %2 MB)"_s.arg( usedGpuMemory ).arg( mGpuMemoryLimit ), 2 );
  }
 
  return unloaded;
}
 
 
QgsRange<float> QgsChunkedEntity::getNearFarPlaneRange( const QMatrix4x4 &viewMatrix ) const
{
  QList<QgsChunkNode *> activeEntityNodes = activeNodes();
 
  // it could be that there are no active nodes - they could be all culled or because root node
  // is not yet loaded - we still need at least something to understand bounds of our scene
  // so lets use the root node
  if ( activeEntityNodes.empty() )
    activeEntityNodes << rootNode();
 
  float fnear = 1e9;
  float ffar = 0;
 
  for ( QgsChunkNode *node : std::as_const( activeEntityNodes ) )
  {
    // project each corner of bbox to camera coordinates
    // and determine closest and farthest point.
    QgsAABB bbox = Qgs3DUtils::mapToWorldExtent( node->box3D(), mMapSettings->origin() );
    float bboxfnear;
    float bboxffar;
    Qgs3DUtils::computeBoundingBoxNearFarPlanes( bbox, viewMatrix, bboxfnear, bboxffar );
    fnear = std::min( fnear, bboxfnear );
    ffar = std::max( ffar, bboxffar );
  }
  return QgsRange<float>( fnear, ffar );
}
 
void QgsChunkedEntity::setShowBoundingBoxes( bool enabled )
{
  if ( ( enabled && mBboxesEntity ) || ( !enabled && !mBboxesEntity ) )
    return;
 
  if ( enabled )
  {
    mBboxesEntity = new QgsChunkBoundsEntity( mRootNode->box3D().center(), this );
  }
  else
  {
    mBboxesEntity->deleteLater();
    mBboxesEntity = nullptr;
  }
}
 
void QgsChunkedEntity::updateNodes( const QList<QgsChunkNode *> &nodes, QgsChunkQueueJobFactory *updateJobFactory )
{
  for ( QgsChunkNode *node : nodes )
  {
    if ( node->state() == QgsChunkNode::QueuedForUpdate )
    {
      mChunkLoaderQueue->takeEntry( node->loaderQueueEntry() );
      node->cancelQueuedForUpdate();
    }
    else if ( node->state() == QgsChunkNode::Updating )
    {
      cancelActiveJob( node->updater() );
    }
    else if ( node->state() == QgsChunkNode::Skeleton || node->state() == QgsChunkNode::QueuedForLoad )
    {
      // there is not much to update yet
      continue;
    }
    else if ( node->state() == QgsChunkNode::Loading )
    {
      // let's cancel the current loading job and queue for loading again
      cancelActiveJob( node->loader() );
      requestResidency( node );
      continue;
    }
 
    Q_ASSERT( node->state() == QgsChunkNode::Loaded );
 
    QgsChunkListEntry *entry = new QgsChunkListEntry( node );
    node->setQueuedForUpdate( entry, updateJobFactory );
    mChunkLoaderQueue->insertLast( entry );
  }
 
  // trigger update
  startJobs();
}
 
void QgsChunkedEntity::pruneLoaderQueue( const SceneContext &sceneContext )
{
  QList<QgsChunkNode *> toRemoveFromLoaderQueue;
 
  // Step 1: collect all entries from chunk loader queue that would get frustum culled
  // (i.e. they are outside of the current view of the camera) and therefore loading
  // such chunks would be probably waste of time.
  QgsChunkListEntry *e = mChunkLoaderQueue->first();
  while ( e )
  {
    Q_ASSERT( e->chunk->state() == QgsChunkNode::QueuedForLoad || e->chunk->state() == QgsChunkNode::QueuedForUpdate );
    const QgsAABB bbox = Qgs3DUtils::mapToWorldExtent( e->chunk->box3D(), mMapSettings->origin() );
    if ( Qgs3DUtils::isCullable( bbox, sceneContext.viewProjectionMatrix ) )
    {
      toRemoveFromLoaderQueue.append( e->chunk );
    }
    e = e->next;
  }
 
  // Step 2: remove collected chunks from the loading queue
  for ( QgsChunkNode *n : toRemoveFromLoaderQueue )
  {
    mChunkLoaderQueue->takeEntry( n->loaderQueueEntry() );
    if ( n->state() == QgsChunkNode::QueuedForLoad )
    {
      n->cancelQueuedForLoad();
    }
    else // queued for update
    {
      n->cancelQueuedForUpdate();
      mReplacementQueue->takeEntry( n->replacementQueueEntry() );
      n->unloadChunk();
    }
  }
 
  if ( !toRemoveFromLoaderQueue.isEmpty() )
  {
    QgsDebugMsgLevel( u"Pruned %1 chunks in loading queue"_s.arg( toRemoveFromLoaderQueue.count() ), 2 );
  }
}
 
 
int QgsChunkedEntity::pendingJobsCount() const
{
  return mChunkLoaderQueue->count() + mActiveJobs.count();
}
 
struct ResidencyRequest
{
    QgsChunkNode *node = nullptr;
    float dist = 0.0;
    int level = -1;
    ResidencyRequest() = default;
    ResidencyRequest( QgsChunkNode *n, float d, int l )
      : node( n )
      , dist( d )
      , level( l )
    {}
};
 
struct
{
    bool operator()( const ResidencyRequest &request, const ResidencyRequest &otherRequest ) const
    {
      if ( request.level == otherRequest.level )
        return request.dist > otherRequest.dist;
      return request.level > otherRequest.level;
    }
} ResidencyRequestSorter;
 
void QgsChunkedEntity::update( QgsChunkNode *root, const SceneContext &sceneContext )
{
  QSet<QgsChunkNode *> nodes;
  QVector<ResidencyRequest> residencyRequests;
 
  using slotItem = std::pair<QgsChunkNode *, float>;
  auto cmp_funct = []( const slotItem &p1, const slotItem &p2 ) { return p1.second <= p2.second; };
  int renderedCount = 0;
  std::priority_queue<slotItem, std::vector<slotItem>, decltype( cmp_funct )> pq( cmp_funct );
  const QgsAABB rootBbox = Qgs3DUtils::mapToWorldExtent( root->box3D(), mMapSettings->origin() );
  pq.push( std::make_pair( root, screenSpaceError( rootBbox, root->error(), sceneContext ) ) );
  while ( !pq.empty() && renderedCount <= mPrimitivesBudget )
  {
    slotItem s = pq.top();
    pq.pop();
    QgsChunkNode *node = s.first;
 
    const QgsAABB bbox = Qgs3DUtils::mapToWorldExtent( node->box3D(), mMapSettings->origin() );
    if ( Qgs3DUtils::isCullable( bbox, sceneContext.viewProjectionMatrix ) )
    {
      ++mFrustumCulled;
      continue;
    }
 
    // ensure we have child nodes (at least skeletons) available, if any
    if ( !node->hasChildrenPopulated() )
    {
      // Some chunked entities (e.g. tiled scene) may not know the full node hierarchy in advance
      // and need to fetch it from a remote server. Having a blocking network request
      // in createChildren() is not wanted because this code runs on the main thread and thus
      // would cause GUI freezes. Here is a mechanism to first check whether there are any
      // network requests needed (with canCreateChildren()), and if that's the case,
      // prepareChildren() will start those requests in the background and immediately returns.
      // The factory will emit a signal when hierarchy fetching is done to force another update
      // of this entity to create children of this node.
      if ( mChunkLoaderFactory->canCreateChildren( node ) )
      {
        node->populateChildren( mChunkLoaderFactory->createChildren( node ) );
      }
      else
      {
        mChunkLoaderFactory->prepareChildren( node );
      }
    }
 
    // make sure all nodes leading to children are always loaded
    // so that zooming out does not create issues
    double dist = bbox.center().distanceToPoint( sceneContext.cameraPos );
    residencyRequests.push_back( ResidencyRequest( node, dist, node->level() ) );
 
    if ( !node->entity() && node->hasData() )
    {
      // this happens initially when root node is not ready yet
      continue;
    }
    bool becomesActive = false;
 
    // QgsDebugMsgLevel( u"%1|%2|%3  %4  %5"_s.arg( node->tileId().x ).arg( node->tileId().y ).arg( node->tileId().z ).arg( mTau ).arg( screenSpaceError( node, sceneContext ) ), 2 );
    if ( node->childCount() == 0 )
    {
      // there's no children available for this node, so regardless of whether it has an acceptable error
      // or not, it's the best we'll ever get...
      becomesActive = true;
    }
    else if ( mTau > 0 && screenSpaceError( bbox, node->error(), sceneContext ) <= mTau && node->hasData() )
    {
      // acceptable error for the current chunk - let's render it
      becomesActive = true;
    }
    else
    {
      // This chunk does not have acceptable error (it does not provide enough detail)
      // so we'll try to use its children. The exact logic depends on whether the entity
      // has additive strategy. With additive strategy, child nodes should be rendered
      // in addition to the parent nodes (rather than child nodes replacing parent entirely)
 
      if ( node->refinementProcess() == Qgis::TileRefinementProcess::Additive )
      {
        // Logic of the additive strategy:
        // - children that are not loaded will get requested to be loaded
        // - children that are already loaded get recursively visited
        becomesActive = true;
 
        QgsChunkNode *const *children = node->children();
        for ( int i = 0; i < node->childCount(); ++i )
        {
          const QgsAABB childBbox = Qgs3DUtils::mapToWorldExtent( children[i]->box3D(), mMapSettings->origin() );
          if ( children[i]->entity() || !children[i]->hasData() )
          {
            // chunk is resident - let's visit it recursively
            pq.push( std::make_pair( children[i], screenSpaceError( childBbox, children[i]->error(), sceneContext ) ) );
          }
          else
          {
            // chunk is not yet resident - let's try to load it
            if ( Qgs3DUtils::isCullable( childBbox, sceneContext.viewProjectionMatrix ) )
              continue;
 
            double dist = childBbox.center().distanceToPoint( sceneContext.cameraPos );
            residencyRequests.push_back( ResidencyRequest( children[i], dist, children[i]->level() ) );
          }
        }
      }
      else
      {
        // Logic of the replace strategy:
        // - if we have all children loaded, we use them instead of the parent node
        // - if we do not have all children loaded, we request to load them and keep using the parent for the time being
        if ( node->allChildChunksResident( mCurrentTime ) )
        {
          QgsChunkNode *const *children = node->children();
          for ( int i = 0; i < node->childCount(); ++i )
          {
            const QgsAABB childBbox = Qgs3DUtils::mapToWorldExtent( children[i]->box3D(), mMapSettings->origin() );
            pq.push( std::make_pair( children[i], screenSpaceError( childBbox, children[i]->error(), sceneContext ) ) );
          }
        }
        else
        {
          becomesActive = true;
 
          QgsChunkNode *const *children = node->children();
          for ( int i = 0; i < node->childCount(); ++i )
          {
            const QgsAABB childBbox = Qgs3DUtils::mapToWorldExtent( children[i]->box3D(), mMapSettings->origin() );
            double dist = childBbox.center().distanceToPoint( sceneContext.cameraPos );
            residencyRequests.push_back( ResidencyRequest( children[i], dist, children[i]->level() ) );
          }
        }
      }
    }
 
    if ( becomesActive && node->entity() )
    {
      mActiveNodes << node;
      // if we are not using additive strategy we need to make sure the parent primitives are not counted
      if ( node->refinementProcess() != Qgis::TileRefinementProcess::Additive && node->parent() && nodes.contains( node->parent() ) )
      {
        nodes.remove( node->parent() );
        renderedCount -= mChunkLoaderFactory->primitivesCount( node->parent() );
      }
      renderedCount += mChunkLoaderFactory->primitivesCount( node );
      nodes.insert( node );
    }
  }
 
  // sort nodes by their level and their distance from the camera
  std::sort( residencyRequests.begin(), residencyRequests.end(), ResidencyRequestSorter );
  for ( const auto &request : residencyRequests )
    requestResidency( request.node );
}
 
void QgsChunkedEntity::requestResidency( QgsChunkNode *node )
{
  if ( node->state() == QgsChunkNode::Loaded || node->state() == QgsChunkNode::QueuedForUpdate || node->state() == QgsChunkNode::Updating )
  {
    Q_ASSERT( node->replacementQueueEntry() );
    Q_ASSERT( node->entity() );
    mReplacementQueue->takeEntry( node->replacementQueueEntry() );
    mReplacementQueue->insertFirst( node->replacementQueueEntry() );
  }
  else if ( node->state() == QgsChunkNode::QueuedForLoad )
  {
    // move to the front of loading queue
    Q_ASSERT( node->loaderQueueEntry() );
    Q_ASSERT( !node->loader() );
    if ( node->loaderQueueEntry()->prev || node->loaderQueueEntry()->next )
    {
      mChunkLoaderQueue->takeEntry( node->loaderQueueEntry() );
      mChunkLoaderQueue->insertFirst( node->loaderQueueEntry() );
    }
  }
  else if ( node->state() == QgsChunkNode::Loading )
  {
    // the entry is being currently processed - nothing to do really
  }
  else if ( node->state() == QgsChunkNode::Skeleton )
  {
    if ( !node->hasData() )
      return; // no need to load (we already tried but got nothing back)
 
    // add to the loading queue
    QgsChunkListEntry *entry = new QgsChunkListEntry( node );
    node->setQueuedForLoad( entry );
    mChunkLoaderQueue->insertFirst( entry );
  }
  else
    Q_ASSERT( false && "impossible!" );
}
 
 
void QgsChunkedEntity::onActiveJobFinished()
{
  int oldJobsCount = pendingJobsCount();
 
  QgsChunkQueueJob *job = qobject_cast<QgsChunkQueueJob *>( sender() );
  Q_ASSERT( job );
  Q_ASSERT( mActiveJobs.contains( job ) );
 
  QgsChunkNode *node = job->chunk();
 
  if ( node->state() == QgsChunkNode::Loading )
  {
    QgsChunkLoader *loader = qobject_cast<QgsChunkLoader *>( job );
    Q_ASSERT( loader );
    Q_ASSERT( node->loader() == loader );
 
    addTileTraceEvent( *this, *node, QgsEventTracing::AsyncEnd, u"Load"_s );
 
    QgsScopedEvent e( "3D", QString( "create" ) );
    // mark as loaded + create entity
    Qt3DCore::QEntity *entity = node->loader()->createEntity( this );
 
    if ( entity )
    {
      // The returned QEntity is initially enabled, so let's add it to active nodes too.
      // Soon afterwards updateScene() will be called, which would remove it from the scene
      // if the node should not be shown anymore. Ideally entities should be initially disabled,
      // but there seems to be a bug in Qt3D - if entity is disabled initially, showing it
      // by setting setEnabled(true) is not reliable (entity eventually gets shown, but only after
      // some more changes in the scene) - see https://github.com/qgis/QGIS/issues/48334
      mActiveNodes << node;
 
      // load into node (should be in main thread again)
      node->setLoaded( entity );
 
      mReplacementQueue->insertFirst( node->replacementQueueEntry() );
 
      emit newEntityCreated( entity );
    }
    else
    {
      node->setHasData( false );
      node->cancelLoading();
    }
 
    // now we need an update!
    mNeedsUpdate = true;
  }
  else
  {
    Q_ASSERT( node->state() == QgsChunkNode::Updating );
 
    // This is a special case when we're replacing the node's entity
    // with QgsChunkUpdaterFactory passed to updatedNodes(). The returned
    // updater is actually a chunk loader that will give us a completely
    // new QEntity, so we just delete the old one and use the new one
    if ( QgsChunkLoader *nodeUpdater = qobject_cast<QgsChunkLoader *>( node->updater() ) )
    {
      Qt3DCore::QEntity *newEntity = nodeUpdater->createEntity( this );
      node->replaceEntity( newEntity );
      emit newEntityCreated( newEntity );
    }
 
    addTileTraceEvent( *this, *node, QgsEventTracing::AsyncEnd, u"Update"_s );
    node->setUpdated();
  }
 
  // cleanup the job that has just finished
  mActiveJobs.removeOne( job );
  job->deleteLater();
 
  // start another job - if any
  startJobs();
 
  if ( pendingJobsCount() != oldJobsCount )
    emit pendingJobsCountChanged();
}
 
void QgsChunkedEntity::startJobs()
{
  while ( mActiveJobs.count() < 4 && !mChunkLoaderQueue->isEmpty() )
  {
    QgsChunkListEntry *entry = mChunkLoaderQueue->takeFirst();
    Q_ASSERT( entry );
    QgsChunkNode *node = entry->chunk;
    delete entry;
 
    QgsChunkQueueJob *job = startJob( node );
    if ( !job->isFinished() )
      mActiveJobs.append( job );
  }
}
 
QgsChunkQueueJob *QgsChunkedEntity::startJob( QgsChunkNode *node )
{
  if ( node->state() == QgsChunkNode::QueuedForLoad )
  {
    addTileTraceEvent( *this, *node, QgsEventTracing::AsyncBegin, u"Load"_s );
 
    QgsChunkLoader *loader = mChunkLoaderFactory->createChunkLoader( node );
    connect( loader, &QgsChunkQueueJob::finished, this, &QgsChunkedEntity::onActiveJobFinished );
    loader->start();
    node->setLoading( loader );
    return loader;
  }
  else if ( node->state() == QgsChunkNode::QueuedForUpdate )
  {
    addTileTraceEvent( *this, *node, QgsEventTracing::AsyncBegin, u"Update"_s );
 
    node->setUpdating();
    connect( node->updater(), &QgsChunkQueueJob::finished, this, &QgsChunkedEntity::onActiveJobFinished );
    node->updater()->start();
    return node->updater();
  }
  else
  {
    Q_ASSERT( false ); // not possible
    return nullptr;
  }
}
 
void QgsChunkedEntity::cancelActiveJob( QgsChunkQueueJob *job )
{
  Q_ASSERT( job );
 
  QgsChunkNode *node = job->chunk();
  disconnect( job, &QgsChunkQueueJob::finished, this, &QgsChunkedEntity::onActiveJobFinished );
 
  if ( node->state() == QgsChunkNode::Loading )
  {
    // return node back to skeleton
    node->cancelLoading();
 
    addTileTraceEvent( *this, *node, QgsEventTracing::AsyncEnd, u"Load"_s );
  }
  else if ( node->state() == QgsChunkNode::Updating )
  {
    // return node back to loaded state
    node->cancelUpdating();
 
    addTileTraceEvent( *this, *node, QgsEventTracing::AsyncEnd, u"Update"_s );
  }
  else
  {
    Q_ASSERT( false );
  }
 
  job->cancel();
  mActiveJobs.removeOne( job );
  job->deleteLater();
}
 
void QgsChunkedEntity::cancelActiveJobs()
{
  while ( !mActiveJobs.isEmpty() )
  {
    cancelActiveJob( mActiveJobs.takeFirst() );
  }
}
 
QList<QgsRayCastHit> QgsChunkedEntity::rayIntersection( const QgsRay3D &ray, const QgsRayCastContext &context ) const
{
  Q_UNUSED( ray )
  Q_UNUSED( context )
  return {};
}