[vtkusers] design disabling filter in pipeline

[Florian Bruckner]

my question is about the general design of a pipeline, when intermediate
filters should be turned on and off during operation. For example i
would like to display my input geometry and then have a switch that
allows to apply a threshold filter and display the filtered output. 

how do i implement this? 

One possiblilty is to hard-code the pipeline and only set the threshold
so that nothing is filtered if i want to get the original output. 

The second way would be to insert and remove the filter into the
pipeline only if it is used. But then i need to keep track of all parts
of the pipeline in order to reset the inputs / outputs correctly. Or is
there a more elegant solution for this method?

what about performance of these methods? is adding a filter slower than
reseting a threshold / clipping range / ... ?

thanks
Flob