In general VTK is a very versatile format, which allows many possible structures. For generic VTK format one can see http://vtk.org. Here only SMASH-specific VTK format is described.

SMASH VTK files contain a snapshot of simulation at one moment of time. VTK output files are written at initialization at event start and every period of time \( \Delta t \), where \( \Delta t \) is regulated by option (see General). For every new output moment a separate VTK file is written. File names are constructed as follows: pos_ev<event>_tstep<output_number>.vtk.

Files contain particle coordinates, momenta, PDG codes, cross-section scaling factors, ID, number of collisions baryon number, strangeness and masses. VTK output is known to work with paraview, a free visualization and data analysis software. Files of this format are supposed to be used as a black box and opened with paraview, but at the same time they are human-readable text files.

There is also a possibility to print a lattice with thermodynamical quantities to vtk files, see Thermodynamics VTK Output.