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Hi all.

I just ran into a curious problem. I tried to generate a buffer around my data, exporting it to GML. The problem is that QGIS won’t open the generated GML.

I found that the GML data contained geometry errors (OGC Simple), and that these in part was made by the Bufferer transformer !??

When I debug run a GeometryValidator->Bufferer->GeometryValidator setup, only running passed+repaired features into the Bufferer, the second GeometryValidator outputs failed geometries, i.e. output by the Bufferer..

Is this a known problem ?

Cheers

Using 2025.2 beta

Definitely a bit weird - are you doing a negative buffer? That can produce collapsed features.

Looking at the parameters there is an option for a Buffer Mode - (Fast and Precise). The doc mentions that geometries can get generalized in the input before being buffered which speeds up performance. What happens if you try switching the mode.

Is there anything which jumps out at you about the features which are invalid? The fact that you have some invalid features already in the dataset makes me wonder just how “valid” the valid features are. 

Would certainly be interesting to isolate one of those features to understand what is going on

We’ve had something similar the other day, creating buffers around buildings and points and then writing them to Geopackage. Some (but not all) would fail on geometry. I worked around it by adding an ArcStroker.

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