[Paraview] XDMF reads as Multi-group Dataset

[Eric Monson]

Hello,

I realize that Xdmf support is in transition, but I'm having trouble  
using the current implementation. (My data is in HDF5 format, so Xdmf  
is the most natural for getting it into ParaView.)

1. Any Xdmf file that can be read by ParaView (3.2.1 or 3.3) doesn't  
keep its intended data "Type" -- it's listed in the Information tab as  
"Multi-group Dataset". This can be reproduced by loading in a *.vti or  
*.vtu file, then save it as *.xmf and then re-read it. Is this a known  
issue? Any ideas for a workaround, even if it's just until Xdmf 2.0  
comes online?  (One resultant problem I'm having is that if I want to  
read in Xdmf and then save as a native VTK XML format, only the VTK  
Multi Group Files (*.vtm) format is listed.)

2. Some of my data are particles, which I used to read in as an  
Unstructured Grid by using the Xdmf PolyVertex topology. Since these  
points are not really connected in any way, (up through ParaView  
3.0.2) I used to start my *.xmf files like this, using just PolyVertex  
and NodesPerElement:

<?xml version="1.0" ?>
<!DOCTYPE Xdmf SYSTEM "Xdmf.dtd" [
<!ENTITY HeavyCellData "test_lucas_hdf_cells.h5">
]>

<Xdmf>
   <Domain Name="test_lucas">
     <Grid Name="Cells">
       <Topology
          Type="PolyVertex"
          NodesPerElement="1001">
       </Topology>
       .....

Maybe this isn't the correct way to do it, but ParaView used to read  
it okay, and now it crashes when trying to read this type of file.  
 From what I can tell (looking at *.vtu files saved as *.xmf from PV  
3.2.1 or 3.3), PV seems to need a "Connections" data structure within  
the Topology definition (which just says each node is connected to the  
next one, 0->1, 1->2, etc.):

<?xml version="1.0" ?>
<!DOCTYPE Xdmf SYSTEM "Xdmf.dtd" [
<!ENTITY HeavyCellData "test_lucas_hdf_cells.h5">
]>

<Xdmf>
   <Domain Name="test_lucas">
     <Grid Name="Cells">
       <Topology  Type="POLYVERTEX"
          Dimensions="1">
         <DataStructure
            DataType="Int"
            Dimensions="1 1001"
            Format="HDF">
            &HeavyCellData;:/simulation1/experiment1/environment1/ 
snapshots/s0/Cells/Connections
         </DataStructure>
       </Topology>
       .....

Is there any way to get ParaView to load an Xdmf unstructured grid  
which doesn't have this Connections data defined? (It's just a bit of  
a pain since this data isn't part of our natural simulation output,  
and to get the data to load into PV I have to generate this extra  
Connections array afterwards.)

Thanks,
Eric

-----------------------------------------------------
Eric E. Monson
Duke Visualization Technology Group