@returns A reference to the @a z displacement module.
@pre This displacement module has been added to this noise module
via a call to SetSourceMod() or SetZDisplaceMod().
@throw new ExceptionNoMod See the preconditions for more
information.
The GetValue() method displaces the input value by adding the output
value from this displacement module to the @a z coordinate of the
input value before returning the output value from the source
module.
Returns the @a z displacement module.
@returns A reference to the @a z displacement module.
@pre This displacement module has been added to this noise module via a call to SetSourceMod() or SetZDisplaceMod().
@throw new ExceptionNoMod See the preconditions for more information.
The GetValue() method displaces the input value by adding the output value from this displacement module to the @a z coordinate of the input value before returning the output value from the source module.