ExtractSurface extracts more than I would like

Hi,

I just started using OpenGeoSys with the intention of extracting the uppermost surface of an unstructured grid in .vtu format. I used the ExtractSurface tool with the following parameters:

-i MyMesh.vtu -o TopSurface.vtu

The following picture shows myMesh (top left), the TopSurface output (top right), and a temporary workaround with a ParaView threshold filter (bottom):

I suppose the multiple ‘top’ slices might be theoretically correct because this is unstructured mesh in format. However, in practice the mesh is defined in layer/row/column format, there is a very clear ‘top’ to the viewer. Is there a way extract the actual top surface only? Note: this is just a simple example mesh for testing, my real meshes will be more interesting!

I seem to be able to get a temporary work-around in ParaView with a threshold filter, but ideally I’m lookign to access the global top elements of the mesh, rather than the local top elements.

Sorry for the late reply. Did you find the reason for the strange behaviour? If not, please, could you provide a small test case such that this behaviour can be reproduced?