[vtk-developers] Optimization of vtkClipDataSet and vtkProbeFilter for large data?

[Mirek]

Dear VTK developers, 

Filters like vtkClipDataSet and vtkProbeFilter, interpolating values of
vtkDataSetAttributes, work perfectly for relatively small data, i.e. if the
clipping is fast and you can have all vtkDataSetAttributes in memory.
However, it looks like there is no option to optimize these filters for
large data. In my case (see details (*) below), data of each quantity is
loaded "on demand" from the disk. The problem is that vtkClipDataSet cannot
interpolate new vtkDataSetAttributes into the existing (clipped)
unstructured grid without recalculating everything, which is unnecessary and
slow. In my old program, all "interpolated points" had information how to
recalculate values of a new quantity (now vtkPointData scalars), which
actually is a simple and fast operation. In case of a tetrahedral mesh, you
just need to have IDs of 4 original mesh nodes and their weights for the
linear interpolation. 

I have spent several days by debugging VTK and looking for a standard
solution. Unfortunately, I have not found any way how to get and save the
interpolation factors so that I could reuse them. The interpolation of
vtkDataSetAttributes is implemented in vtkTetra::Clip and most of important
functions (vtkTetra::Clip,  vtkDataSetAttributes::InterpolateEdge, ...) are
not virtual => it will not be easy to modify the filter. Before investing
time into the development of a new filter, I'd like to ask: Did I miss
something?  Is there an existing solution for this problem?

Thank you
Mirek      

(*) In my case the data can be really large: unstructured FE-meshes with up
to 50 mil. nodes and time-varying results (10-200 different quantities
defined by values at mesh nodes, while there can be 100 - 10000 time
layers).    




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