[vtkusers] writing EnSight files - Error: No BlockID was found

[Martin Baumann]

Hi,

I am sorry for asking a similar question.
I have some more information that might be of interest concerning this 
problem.
I am still trying to write EnSight files, and get the BlockID error.

I get the vtkUnstructuredGrid that I am going to save from an 
vtkUnstructuredGridReader object.
By default my vtkUnstructuredGrid doesn't contain a block id array.

The vtkUnstructuredGrid object does contain no cell-Data array at all:

  #Points : 9261
    Point-Data: #Arrays: 4
       u_x, 1 component(s)
       u_y, 1 component(s)
       u_z, 1 component(s)
       rho, 1 component(s)
  #Cells:   8000
     Cell-Data: #Arrays: 0


I read in the documentation for vtkModelMetadata:
Your vtkUnstructuredGrid 
<http://www.vtk.org/doc/release/5.0/html/a02147.html> must have a cell 
array giving the block ID for each cell.
So I have to create one?
Do I have to use vtkModelMetadata to create the cell data that is missing?

How can I create a Block Id for an vtkUnstructuredGrid?
Is this array of block ids already existing or do I have to create it?
What exactly is a block id for a cell? Is it for all cells the same?
Does each cell has its unique id?

Questions questions questions ... :-(

Regards, M.B.