[Paraview] "Inner boundary" with Reflection Filter

[Bernhard Gschaider]

I'm trying to visualize data from a simulation of a symmetrical
system. The simulation was only done for one half of the system, but
in order to ease the understanding I want to show the complete
system. 

In order this achieve this I import the data and pipe it trough the
reflection filter (with copying of the input enabled). All further
operations are done with the output of that filter.

Must of the things work OK, but I also want to show a part of the
surface of the simulation data. I apply "Extract Surface" to the
output of the reflection filter and the use "Clip" to cut away the
parts, that are not of interest.

The problem is, that now the reflection plane in the middle of the
model is visible (which is not wanted) and I have no easy way to clip
it away.

The problem seems to be, that Paraview/VTK treats the original data
and the reflection as two seperate entities.

I tried the "Clean To Grid" filter (amongst others) to solve that
problem. Now the "Connectivity" filter says that there is only one
region, but when I extract the surface from that filter the symmetry
plane is still visible.

Am I trying to do something, that ParaView can't do, or is there way
to do it?