[vtkusers] Higher order elements in VTU files

[Mikael Öhman]

Hi. I'm a developer for a finite element code which primarily uses VTK
for post-processing. I'm looking for means to export NURBS elements
and other higher order types.
I found both in vtkCellType.h  and on
http://www.paraview.org/Wiki/ParaView/Users_Guide/VTK_Data_Model
a lists many of the types i would wish to find, but they are not
documented in the file format guide.
In fact, all cell types from VTK_PARAMETRIC_* and VTK_HIGHER_* doesn't
seem to be implemented.
I can only imagine how hard it would be to try and fit general
parametric functions into the same procedure, as the nodes can have
arbitrary positions in the mapped coordinate system.

1. Are they just placeholders?
2. Is there any plan to implement these parametric and higher order elements?
3. Can I export the bi-quadratic and tri-quadratic element types to
*.vtu files (even though they are not listed in file format
documentation)? i.e. the file format documentation should probably be
updated.