Command line running (Linux)
PlanarRad can be run from the command line without opening the GUI window, the run parameters are specified in a simple text file. The executable for command line running is called "slabtool_free", and if the parameters are saved in the file 'params.txt' then under Linux it is run like this:
slabtool_free params=params.txt
Assuming 'slabtool_free' is in your path. Note there are no spaces around the '='.
The GUI version of PlanarRad automatically builds files for 1) sky radiance distribution; 2) the air-water interface and 3) the phase function as determined from the settings. The command line version requires these files to be pre-built and the paths to them will be specified in the input text file. The easiest way to build these files is to run the GUI version of PlanarRad with required settings and the files can be found in the output directory.
For example, following the instructions here: BRDF of a material with isotropic phase function will gives rise to these files: