[Paraview] Multiple Domains with XDMF

[Truman Ellis]

I essentially have two grids with different solution variables defined 
on each one. I am using the XDMF format to output the data. When I 
create a spatial collection of the two grids, the solution variables 
show up as "partial" data in Paraview. Say solution variable u lives on 
grid 1 while f lives on grid 2. If I color by u, grid 2 shows up as some 
solid color that doesn't go away unless I turn off the block that 
corresponds to grid 2. And vice versa for f.

I read that XDMF supports multiple domains, which sounded like it might 
be the right solution for this problem. But when I load such a mesh into 
Paraview, it only picks up on the last defined domain. It seems like 
having different solution variables on different grids is a common 
problem, so I'm wondering if anyone has a cleaner solution than 
selectively turning on and off the blocks corresponding to the solution 
variable I am currently considering.