Documentation/UserGuide/vtk Files

Much like binary dumps, vtk files contain an unformatted write of selected variables over all zones, with the data written in VTK legacy format. Each file contains data at a single time. A new file is created whenever the integration time exceeds an integer multiple of <output>/dt. At the end of execution, the lesser of tlim/dt or <time>/nlim sequentially numbered files will be created. Since they are unformatted, the outputs are compact, and are most useful for 3D data. The VisIt visualization tool can read Athena vtk files directly.

vtk dumps contain all the primitive or conserved variables. vtk outputs contain only a single variable. Each is described in more detail below.

Both vtk dumps and outputs are hardwired to be single precision only. If data is needed in double precision, then the dump_vtk.c function would need to be modified appropriately, and used as a new user-defined output function.

vtk Dumps

The following example shows an <output> block in an input file that generates a vtk dump of the primitive variables:

out_fmt = vtk               # vtk data dump
out     = prim              # variables to be dumped
dt      = 0.1               # time increment between outputs

vtk files consist of an ASCII header containing information about the dimensions and variables contained in the file, followed by the unformatted data itself. Since the header is ASCII format, vtk files can be edited to read the header information.

vtk Outputs

Single variables can also be output as vtk files. In addition, new (user-defined) variables can be output as vtk files by following the steps described in User-defined Outputs. For example, the following shows an <output> block in an input file that generates a vtk dump of a user defined variable:

out_fmt = vtk               # vtk data dump
out     = dVy               # user defined variable: y-velocity fluctuations
id      = dVy               # file name string identifier
dt      = 0.1               # time increment between outputs
usr_expr_flag = 1           # user defined variable

vtk output files are created by the function output_vtk.c.