Have done a simple magnet falling (under free fall) and how the magnetic field lines move along with it.
In order to change the number of field lines, please edit the variable NField in the variables page.
Thank to Wolfgang Christian Magnetic Dipole Field 3D Model at http://www.opensourcephysics.org/document/ServeFile.cfm?ID=12361&DocID=3083
I have modified the magnetic field line codes so that the magnetic field lines are drawn at the start and it is not drawn dynamically.
Please press the reset button if you can't see the magnetic field lines.