[vtkusers] Separation of <Points> and <Cells> datablocks from Unstructured Grid (.vtu) files

[Frank Everdij]

Dear all,

This has been asked before (see 
http://public.kitware.com/pipermail/vtkusers/2008-August/096457.html and 
http://public.kitware.com/pipermail/vtkusers/2008-February/094460.html), 
but apparently no definitive answer was given, so in the light of new 
advancements in the VTK toolkit, i'll ask again:

For a while now i am using a .pvd file pointing to a series of .vtu 
files to perform time plotting of vectors (point displacements) and 
scalars (point strain) of 2D grids in finite element computations.
This works fine, but in order to scale up the grids i run into a problem 
of having to repeat <Points> and <Cells> DataArrays in every <Piece> 
block of every .vtu file.
Since these <Points> and <Cells> DataArrays are the same for all .vtu 
files, i would love to put these in a separate file to save diskspace, 
f.i. for points:

<VTKFile type="UnstructuredGrid" version="0.1">
  <UnstructuredGrid>
   <Piece NumberOfPoints="12" NumberOfCells="14">
    <Points>
     <DataArray type="Float32" NumberOfComponents="3" format="ascii" 
Source="allpoints.txt>

or

     <DataArray Source="allpoints.xml>

or something similar. I am only interested in the datafile description, 
not the VTK calls, since i am not using VTK to produce the datafiles.

Can this in principle be done? And if so, how would it look like when 
viewing this with, let's say, Paraview 3.98.1?
I've looked at .vtm and .pvtu file descriptions, but these deal 
specifically with substructuring of points and cells data. Both of these 
require a <Piece> block with full or partial <Points> and <Cells> blocks.

Alternatively i'm fine with having a monolithic .vtu file with one 
<Points> and <Cells> block and multiple <PointData> and <CellData> with 
time-tags.
This seems to be implemented already in 2008, but can anyone give me a 
hint of doing this in a .vtu file?

-- 
drs Frank Everdij  Email:F.P.X.Everdij at tudelft.nl
Tel:+31 15 2788202 Room:CT-6.34
Developer SSC-ICT at Delft University of Technology