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I'm trying to use the geometry generator in symbology for a line layer. Specifically I want to smooth out the lines using smooth($geometry,5).

Unfortunately QGIS crashes every time I try to implement this. The data is stored in a GPKG. The GPKG contains other layers, but I have exported this particular layer to a separate GPKG file for testing.

It works fine if I export the lines to shapefile, but the data needs to be stored in a GPKG so I need to get this working.

Interestingly, the original GPKG file also contains a layer of polygons and I have successfully implemented the smooth($geometry,5) for these without any issues.

Happy to send through the GPKG file and see if someone can figure out what the problem is. I've run the geometry checker (Check Validity tool) on it and doesn't show any issues.

I'm running version 3.12.3 of QGIS.

enter image description here enter image description here

Crash Report:

Crash ID: 86223684825a81f552f396a7391a484f166dfa07 Stack Trace QVector::QVector qvector.h:358 QgsLineString::QgsLineString : qgis::make_unique qgis.h:425 smoothCurve qgsgeometry.cpp:3091 QgsGeometry::smoothLine qgsgeometry.cpp:3177 QgsGeometry::smooth qgsgeometry.cpp:3046 fcnSmooth qgsexpressionfunction.cpp:2463 QgsStaticExpressionFunction::func qgsexpressionfunction.h:447 QgsExpressionFunction::run qgsexpressionfunction.cpp:102 QgsExpressionNodeFunction::evalNode qgsexpressionnodeimpl.cpp:901 QgsExpressionNode::eval qgsexpressionnode.cpp:29 QgsExpression::evaluate qgsexpression.cpp:373 QgsGeometryGeneratorSymbolLayer::render qgsgeometrygeneratorsymbollayer.cpp:200 QgsSymbol::renderUsingLayer qgssymbol.cpp:716 QgsLineSymbol::renderPolyline qgssymbol.cpp:1967 QgsSymbol::renderFeature qgssymbol.cpp:915 QgsFeatureRenderer::renderFeature qgsrenderer.cpp:130 QgsVectorLayerRenderer::drawRenderer qgsvectorlayerrenderer.cpp:328 QgsVectorLayerRenderer::render qgsvectorlayerrenderer.cpp:284 QgsMapRendererParallelJob::renderLayerStatic qgsmaprendererparalleljob.cpp:353 QtConcurrent::MapKernel::iterator,QtConcurrent::FunctionWrapper1 >::runIteration qtconcurrentmapkernel.h:69 QtConcurrent::MapKernel::iterator,QgsImageOperation::ProcessBlockUsingPixelOperation >::runIterations qtconcurrentmapkernel.h:78 QtConcurrent::IterateKernel::iterator,void>::forThreadFunction qtconcurrentiteratekernel.h:256 QtConcurrent::ThreadEngineBase::run : QThreadPoolPrivate::reset : QThread::start : BaseThreadInitThunk : RtlUserThreadStart : QGIS Info QGIS Version: 3.12.3-Bucure?ti QGIS code revision: 8234261527 Compiled against Qt: 5.11.2 Running against Qt: 5.11.2 Compiled against GDAL: 3.0.4 Running against GDAL: 3.0.4 System Info CPU Type: x86_64 Kernel Type: winnt Kernel Version: 10.0.18363

Happy to supply any other information as needed.

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  • Link to GPKG file: link Commented Jun 15, 2020 at 3:09

1 Answer 1

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It appears the line layer in your gpkg is of CompoundCurveZ geometry and QGIS's smooth() function doesn't seem to play well with that.

When I saved your layer to LineStringZ/MultiLineStringZ geometry using QGIS, however, QGIS's geometry generator/field calculator still detects $geometry as being CompoundCurveZ/MultiCurveZ and crashes when smooth() is applied.

As an interim workaround, I "converted" the geometry to LineStringZ by simplifying it with a tolerance of 0:

smooth(simplify($geometry,0),5)

This produced smoothed results (blue) without crashing QGIS.

enter image description here

I suspect there is a bug in QGIS at play here.

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  • Thank you so much she_weeds... Works perfectly. Really appreciate your help! I suspect you may well be correct regarding a possible QGIS bug. Commented Jun 16, 2020 at 2:46

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