Perhaps the most common use of FISH is to customize model results. Providing this ability was the original motivation for its introduction into Itasca software. FISH allows the user to plot any quantity of interest in the model without requiring addition of a bewildering variety of rarely-used options on a menu tree somewhere. The following is an example of a script that calculates, over the entire model, the normal and shear stress components on a particular plane of orientation. It also creates a flag (fail, line 9) that indicates if failure would occur on that plane, given a specific friction angle (tauCrit, line 8).
Compressive stresses are negative in FLAC3D (note the definition of tauCrit on line 8). The following is a plot of the result, looking at a cut-away plane at the same orientation, from the “Pillar Loads At Intersecting Tunnels” example problem (See Examples Index/FLAC3D Examples/Example Applications). Note that FLAC3D legend entries can be customized to make the content of the plot clearer — in this case fail evaluates to Boolean values (“true”, “false”) but on the plot legend these are re-labeled “Failed” and “Stable”.