I see, the Contour filter of ParaView is actually an isosurface sampling.
I’m not sure if you can do this with OpenFOAM but a better pipeline would be:
- Clip with scalars (using the same array and value than the isosurface)
- Extract surface (in order to reduce 3D dataset to 2D surface)
- Generate normals (to get a smooth surface)
The result should be something equivalent to the isosurface intersected with a box.