Combine multiple ExodusII results into single geometry

I am attempting to load multiple ExodusII results into a single geometry. The results are from a set of simulations that are performed independent, but are all related to the same multi-physics simulation.

Attached is my failed attempt to use vtkMultiBlockMergeFilter, which I am not sure is the correct approach. Mainly because I would expect that the number of input ports would need to be set, but that is not possible from python.

It will render two of the 5 images supplied, but throws an error: “Case not currently handled”, but the message is a bit lacking as is my ability to determine the “Case” from the source code.

$ ./ ../tests/input/multiapps_out_sub*.e --variable u --timestep 2
ERROR: In ../Filters/General/vtkMultiBlockMergeFilter.cxx, line 171
vtkMultiBlockMergeFilter (0x7f95b0443180): Case not currently handled.

ERROR: In ../Common/ExecutionModel/vtkExecutive.cxx, line 782
vtkCompositeDataPipeline (0x7f95b0443840): Algorithm vtkMultiBlockMergeFilter(0x7f95b0443180) returned failure for request: vtkInformation (0x7f95b0444130)
  Debug: Off
  Modified Time: 1947
  Reference Count: 1
  Registered Events: (none)

You can execute the attached script to reproduce the error. I would appreciate assistance and guidance to the best approach to perform such an operation. Eventually I would like to be able to run this script using mpi4py where each file is loaded on it’s own processor, but just need to get it working in serial for now. I would be happy to submit the resulting script(s) to the examples. Thanks for your time.

I am running the script on macOS using python 3.8 and VTK8.2 installed from conda.

./ multiapps_out_sub*.e --variable u --timestep 2 (2.1 KB)

multiapps_out_sub0.e (55.8 KB)
multiapps_out_sub1.e (55.8 KB)
multiapps_out_sub2.e (55.8 KB)
multiapps_out_sub3.e (55.8 KB)
multiapps_out_sub4.e (55.8 KB)

Of course, soon after posting I found a solution using vtk.vtkMultiBlockDataSet and vtk.vtkExtractBlock (

I would still appreciate feedback that this is a proper method. (2.2 KB)