For this example, we create a simple model of a tunnel interactively using the 2D extrusion tool. The tool's data and the resulting zones are shown below. Note that the points used for tunnel are marked, in green, as a group named Tunnel.
Using this as a template, we use the State Record pane to create a data file named create_tunnel.dat that reproduces this geometry. Then we can create a parameterized data file that allows us to test various tunnel locations while only changing one value (tunnel_height defined on line 3).
As seen on line 8, this example demonstrates the ability for FISH to be substituted for a value anywhere within a data file.
Note that things like material properties, tunnel cross-section, and pretty much anything involved in the model can be parameterized in such a fashion – sometimes just with parameter replacement in the data file as seen here, sometimes with the use of FISH functions (as seen above in the Model Creation section). This allows quick and easy exploration of the parameter space of a model that requires set up once and only once.