[vtkusers] How to disable a VTK filter that is connected to a VTK pipeline

[Jeff Baumes]

> nextFilter->SetInput(reader->GetOutput());
> //nextFilter->SetInput(lastFilter->GetOutput());

You should really use this new method instead of SetInput/GetOutput:

nextFilter->SetInputConnection(reader->GetOutputPort());

> When I want to test what happens when I skip a filter. It would make a lot
> more sense to call lastFilter->Disable(). In cases where the output type is
> the same as the input type, we could make Disable() just pass the input
> through to the output. In cases where they DONT match, I don't think it
> makes sense to disable the filter.
> Any comments from the devels?

Conceptually this sounds like a reasonable idea. But Disable() would
only make sense on filters with one input and one output that do not
change the type of the input. It would be confusing what would happen
with multiple inputs/outputs, or if the filter converts from one type
to another. So I don't think it makes sense to have a Disable() at the
vtkAlgorithm level. And there is no superclass for "algorithms with
one input, one output, and the type doesn't change", so Disable()
would probably have to be implemented multiple places.

If someone still wants to look into this, vtkPassThrough is the filter
logic that implements the "disabled" state you want.

Jeff