[Paraview] time filters in paraview

[David C. Thompson]

> I want to create some vtk (and paraview) filters that do time filtering of
> data (e.g. low-pass filtering, integrals, derivatives). 
> 
> For example, in paraview the user would read a data file, then choose 'DSP
> Filter' from the 'Filter' pull-down menu. The user would then either choose
> a stock filter setting, or enter their own filter weights. Finally the user
> would select a cell or point variable array from the input data set. The
> filter would be applied to this array.
> 
> The big problem is that it seems that paraview (and vtk) is geared toward
> accessing one timestep (one vtkDataSet) at a time. These kinds of filters
> need to access multiple input timesteps (and previous output timesteps) in
> order to generate an output.  I havent seen any examples of multiple
> timesteps being passed through the pipeline.
> 
> Has anyone looked at this before? Can anyone direct me to examples of
> something related that has been done?

I think the current recommendation is to create a vtkDataSet for each
time step and use a filter that accepts multiple inputs (such as
vtkInterpolateDataSetAttributes) to perform filtering on them. This is
fine for work such as computing derivatives/integrals but can be
problematic when a computation requires small subsets of a mesh but over
a large time span since many readers don't allow you to request a
particular spatial subset of a grid be read.

	David