Wrong mesh volume

I constructed a closed mesh through drape and join operations. When calculating the volume ( metric settings) it is totally wrong (4.2 m^3 instead of 8.5 m^2), i.e. compare to boundingbox volume (18 m^3). Attached is the file.

What is wrong with the mesh?

Stefanvolume.3dm (279.8 KB)

It looks like the mesh has some flipped normals. After running UnifyMeshNormals on it the volume reports 9.6 cubic meters.

Wonderful, thank you very much for identifying the problem of the mesh.

Do you know a resource for mesh operations (video, command examples) that helps understanding all mesh related commands?

The commands to be aware of if you’re working with meshes will all have the word Mesh in them… for the most part. Just Type Mesh in the command line and you’ll get an autocomplete list even if mesh is not the first word in the command. If you then have the Help panel visible, you’ll interactively see the corresponding help pages for any command you choose.