Fix elevation profile on virtual point cloud (qgis#59073)

* Fix elevation profile on virtual point cloud

(fix qgis#54728)

* Update src/core/pointcloud/qgspointcloudlayerprofilegenerator.cpp

---------

Co-authored-by: Nyall Dawson <[email protected]>

Author: dvdkon

src/core/pointcloud/qgspointcloudlayerprofilegenerator.cpp

@@ -389,12 +389,23 @@ bool QgsPointCloudLayerProfileGenerator::generateProfile( const QgsProfileGenera
   // this is not AT ALL thread safe, but it's what QgsPointCloudLayerRenderer does !
   // TODO: fix when QgsPointCloudLayerRenderer is made thread safe to use same approach
 
-  QgsPointCloudIndex *pc = mLayer->dataProvider()->index();
-  if ( !pc || !pc->isValid() )
+  QVector<QgsPointCloudIndex *> indexes;
+  QgsPointCloudIndex *mainIndex = mLayer->dataProvider()->index();
+  if ( mainIndex && mainIndex->isValid() )
+    indexes.append( mainIndex );
+
+  // Gather all relevant sub-indexes
+  const QgsRectangle profileCurveBbox = mProfileCurve->boundingBox();
+  for ( const QgsPointCloudSubIndex &subidx : mLayer->dataProvider()->subIndexes() )
   {
-    return false;
+    QgsPointCloudIndex *index = subidx.index();
+    if ( index && index->isValid() && subidx.polygonBounds().intersects( profileCurveBbox ) )
+      indexes.append( subidx.index() );
   }
 
+  if ( indexes.empty() )
+    return false;
+
   const double startDistanceOffset = std::max( !context.distanceRange().isInfinite() ? context.distanceRange().lower() : 0, 0.0 );
   const double endDistance = context.distanceRange().upper();
 
@@ -433,9 +444,13 @@ bool QgsPointCloudLayerProfileGenerator::generateProfile( const QgsProfileGenera
   mSearchGeometryInLayerCrsGeometryEngine->prepareGeometry();
   mMaxSearchExtentInLayerCrs = mSearchGeometryInLayerCrs->boundingBox();
 
-  const IndexedPointCloudNode root = pc->root();
-
   double maximumErrorPixels = context.convertDistanceToPixels( mMaximumScreenError, mMaximumScreenErrorUnit );
+  if ( maximumErrorPixels < 0.0 )
+  {
+    QgsDebugError( QStringLiteral( "Invalid maximum error in pixels" ) );
+    return false;
+  }
+
   const double toleranceInPixels = context.convertDistanceToPixels( mTolerance, Qgis::RenderUnit::MapUnits );
   // ensure that the maximum error is compatible with the tolerance size -- otherwise if the tolerance size
   // is much smaller than the maximum error, we don't dig deep enough into the point cloud nodes to find
@@ -444,42 +459,6 @@ bool QgsPointCloudLayerProfileGenerator::generateProfile( const QgsProfileGenera
   if ( toleranceInPixels / 4 < maximumErrorPixels )
     maximumErrorPixels = toleranceInPixels / 4;
 
-  const QgsRectangle rootNodeExtentLayerCoords = pc->nodeMapExtent( root );
-  QgsRectangle rootNodeExtentInCurveCrs;
-  try
-  {
-    QgsCoordinateTransform extentTransform = mLayerToTargetTransform;
-    extentTransform.setBallparkTransformsAreAppropriate( true );
-    rootNodeExtentInCurveCrs = extentTransform.transformBoundingBox( rootNodeExtentLayerCoords );
-  }
-  catch ( QgsCsException & )
-  {
-    QgsDebugError( QStringLiteral( "Could not transform node extent to curve CRS" ) );
-    rootNodeExtentInCurveCrs = rootNodeExtentLayerCoords;
-  }
-
-  const double rootErrorInMapCoordinates = rootNodeExtentInCurveCrs.width() / pc->span(); // in curve coords
-
-  const double mapUnitsPerPixel = context.mapUnitsPerDistancePixel();
-  if ( ( rootErrorInMapCoordinates < 0.0 ) || ( mapUnitsPerPixel < 0.0 ) || ( maximumErrorPixels < 0.0 ) )
-  {
-    QgsDebugError( QStringLiteral( "invalid screen error" ) );
-    return false;
-  }
-  double rootErrorPixels = rootErrorInMapCoordinates / mapUnitsPerPixel; // in pixels
-  const QVector<IndexedPointCloudNode> nodes = traverseTree( pc, pc->root(), maximumErrorPixels, rootErrorPixels, context.elevationRange() );
-  if ( nodes.empty() )
-  {
-    return false;
-  }
-
-  const double rootErrorInLayerCoordinates = rootNodeExtentLayerCoords.width() / pc->span();
-  const double maxErrorInMapCoordinates = maximumErrorPixels * mapUnitsPerPixel;
-
-  mResults = std::make_unique< QgsPointCloudLayerProfileResults >();
-  mResults->copyPropertiesFromGenerator( this );
-  mResults->mMaxErrorInLayerCoordinates = maxErrorInMapCoordinates * rootErrorInLayerCoordinates / rootErrorInMapCoordinates;
-
   QgsPointCloudRequest request;
   QgsPointCloudAttributeCollection attributes;
   attributes.push_back( QgsPointCloudAttribute( QStringLiteral( "X" ), QgsPointCloudAttribute::Int32 ) );
@@ -515,22 +494,75 @@ bool QgsPointCloudLayerProfileGenerator::generateProfile( const QgsProfileGenera
 
   request.setAttributes( attributes );
 
-  switch ( pc->accessType() )
+  mResults = std::make_unique< QgsPointCloudLayerProfileResults >();
+  mResults->copyPropertiesFromGenerator( this );
+  mResults->mMaxErrorInLayerCoordinates = 0;
+
+  QgsCoordinateTransform extentTransform = mLayerToTargetTransform;
+  extentTransform.setBallparkTransformsAreAppropriate( true );
+
+  const double mapUnitsPerPixel = context.mapUnitsPerDistancePixel();
+  if ( mapUnitsPerPixel < 0.0 )
+  {
+    QgsDebugError( QStringLiteral( "Invalid map units per pixel ratio" ) );
+    return false;
+  }
+
+  for ( QgsPointCloudIndex *pc : std::as_const( indexes ) )
   {
-    case QgsPointCloudIndex::AccessType::Local:
+    const IndexedPointCloudNode root = pc->root();
+    const QgsRectangle rootNodeExtentLayerCoords = pc->nodeMapExtent( root );
+    QgsRectangle rootNodeExtentInCurveCrs;
+    try
     {
-      visitNodesSync( nodes, pc, request, context.elevationRange() );
-      break;
+      rootNodeExtentInCurveCrs = extentTransform.transformBoundingBox( rootNodeExtentLayerCoords );
     }
-    case QgsPointCloudIndex::AccessType::Remote:
+    catch ( QgsCsException & )
     {
-      visitNodesAsync( nodes, pc, request, context.elevationRange() );
-      break;
+      QgsDebugError( QStringLiteral( "Could not transform node extent to curve CRS" ) );
+      rootNodeExtentInCurveCrs = rootNodeExtentLayerCoords;
+    }
+
+    const double rootErrorInMapCoordinates = rootNodeExtentInCurveCrs.width() / pc->span(); // in curve coords
+    if ( rootErrorInMapCoordinates < 0.0 )
+    {
+      QgsDebugError( QStringLiteral( "Invalid root node error" ) );
+      return false;
+    }
+
+    double rootErrorPixels = rootErrorInMapCoordinates / mapUnitsPerPixel; // in pixels
+    const QVector<IndexedPointCloudNode> nodes = traverseTree( pc, pc->root(), maximumErrorPixels, rootErrorPixels, context.elevationRange() );
+
+    const double rootErrorInLayerCoordinates = rootNodeExtentLayerCoords.width() / pc->span();
+    const double maxErrorInMapCoordinates = maximumErrorPixels * mapUnitsPerPixel;
+
+    mResults->mMaxErrorInLayerCoordinates = std::max(
+        mResults->mMaxErrorInLayerCoordinates,
+        maxErrorInMapCoordinates * rootErrorInLayerCoordinates / rootErrorInMapCoordinates );
+
+    switch ( pc->accessType() )
+    {
+      case QgsPointCloudIndex::AccessType::Local:
+      {
+        visitNodesSync( nodes, pc, request, context.elevationRange() );
+        break;
+      }
+      case QgsPointCloudIndex::AccessType::Remote:
+      {
+        visitNodesAsync( nodes, pc, request, context.elevationRange() );
+        break;
+      }
     }
+
+    if ( mFeedback->isCanceled() )
+      return false;
   }
 
-  if ( mFeedback->isCanceled() )
+  if ( mGatheredPoints.empty() )
+  {
+    mResults = nullptr;
     return false;
+  }
 
   // convert x/y values back to distance/height values