Using FISH

FISH input (symbols or inline functions) can be supplied to specify the position of a point or a control point in an extrusion set, as described in Creating Points and Edges.

When FISH symbols or inline functions are provided for values this way, it is critical to remember that the FISH input is only evaluated after it has been entered. As a result, there are a range of possible outcomes that it is useful to understand and anticipate. If a symbol or inline function evaluates to a usable value, then that value is used and all proceeds normally. If a symbol for a variable that has not been initialized is supplied, a dialog will appear asking you to supply a valid initial value for the symbol. If a symbol for a variable evaluates to an unacceptable value, an error results. If an inline function evaluates to an unacceptable value, an error also results.

When using a symbol for a function, there are additional considerations. The supplied symbol will produce an error if the function returns an unacceptable value. It will also produce an error if the function’s arguments are not also supplied when the symbol is given. Lastly, and critically, whatever actions the function performs prior to returning a value will occur, regardless of whether the return value produces an error or not. It is up to the user to know the contents of the function, how it will affect the model, and the nature of its return value. FLAC3D has no way to validate or error check in advance to prevent unintended effects when the function is supplied.