Ok let me clarify things:
- the restart works with the filtering, in x y z. once I corrected the mesh etc. and also used 0.01599999999 instead of 0.016 :).
- I got confused because I expected the GUI to display only particles that will be kept in, sorry about this! If that can happen in the future, great, otherwise it is still working.
- The restart with the particles that are really stiff works if we do not reset the particle velocity to 0 at the moment of writing particle_output.csv; this is not something I knew but is somewhat intuitive. Happy days!