Filter with single scalar o/p

Bill Lorensen wlorens1 at
Thu Aug 19 18:28:55 EDT 1999

         look in contrib/vtkMassProperties. It's an object that is not a 
filter, just computes some numbers.
Not everything needs to be a filter.


At 01:56 PM 8/19/99 +0100, John Biddiscombe wrote:
>Dear All,
>Suppose you have a filter which takes as input a (possibly very large)
>vtkStructuredPoints dataset and generates as its output a single value.
>(say) 5.334
>Is there any point making this a proper vtkFilter, rather than just a
>subroutine in some library of code.
>Clearly there's a lot of baggage associated with a vtkFilter - most of
>which in this case is not required.
>For programs dealing with large quantities of data and using the vtk
>Pipeline methodology, it does seem to be a useful thing to have.
>2 questions
>1) would a StructuredPoints dataset with 1 dimension and 1 scalar be the
>best storage facility for this (or a new DatasetToScalar filter superclass)
>2) Can anyone suggest a more efficient means of utilizing this kind of
>algorithm - by which I mean a better way of generating single valued
>outputs without losing the pipeline style.
>Perhaps other users have also required a parameter supplied to a filter (eg
>SetHeight(...) as opposed to a whole dataset) to change as a result of
>other pipeline changes. As yet, there only seems to be an ->Update() on
>Filters or ProcessObjects and not to parameters....
>Your views appreciated
>John B

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