[Paraview] XDMF Set

[Chris Richardson]

I would like to be able to specify data, or subsets of data in the XDMF
format with Edge or Facet sets.

According to the header file of XdmfSet.h:

XdmfSet is a Class that handles sets of nodes,cells,faces, and edges
	on an XdmfGrid. They may be centered on the Node, Edge,
	Face, Cell. An XdmfSet can have from 1 to 3 DataItems. The last 
DataItem
         is always the "Ids" or the indexes into Nodes, Cells, etc. If 
SetType is
         "Face" or "Edge", the First DataItem defines the CellIds. If 
SetType is
         "Edge" second DataItem defines FaceIds

I have two questions:

1) What is the purpose of the FaceIds for a set of Edges?

 From what I can tell, using ParaView, the three dataitems provide:
global CellIDs, unused FaceIDs, cell-local EdgeIds

e.g. in this case, the first DataItem "0 0 1 1" lists the cells,
      the second DataItem "0 1 2 3" is ignored, and the third DataItem "0 
1 0 2"
      lists the cell-local Edges which have data attached?

  <Set SetType="Edge" Name="edgeSet">
           <DataItem NumberType="Int" Dimensions="4" Format="XML">
               0 0 1 1
           </DataItem>
           <DataItem NumberType="Int" Dimensions="4" Format="XML">
               0 1 2 3
           </DataItem>
           <DataItem NumberType="Int" Dimensions="4" Format="XML">
               0 1 0 2
           </DataItem>
           <Attribute Name="Set Values" Center="Edge">
               <DataItem Format="XML" Dimensions="4">
               100 200 400 600
               </DataItem>
           </Attribute>
       </Set>

Is that correct?

2) How can I specify an Edge set in 2D? Nothing seems to work in this 
case,
    as ParaView complains that the cells have invalid Faces.


-- 
Chris Richardson
BP Institute
Madingley Road
Cambridge CB3 0EZ