[Paraview] Particles-in-Cells: Two XDMF files?

[Huebl, Axel]

Hi ParaView mailing list,


we are adding paraview/xdmf support to our particle-in-cell code
PIConGPU [1] right now. To start with the general topology:

The particle in cell algorithm stores field data (scalars and vectors)
on a grid, in the simplest case a 3DCoRectMesh. In between the mesh
points live particles, described with a Polyvertex topology.

The problem that now arises: we would like to describe both grid and
polyvertex data in the *same xdmf file*.

Doing so, e.g. by combining them on the <Domain> level in two separate
"Temporal Collections" causes ParaView to refuse volume-rendering the
fields (not available in the drop down menu).
Adding two Domains to one file causes ParaView to omit the second data
domain during load.
Adding both grid types in the same "Temporal Collection" causes a crash.

Do we really have to write two xdmf files or did we miss a point?

A snippet of our data structures, stored in a hdf5 file per time step:

<?xml version="1.0" ?>
<Xdmf>
  <Domain>
    <Grid CollectionType="Temporal" GridType="Collection" Name="Grids">
      <Grid GridType="Uniform" Name="Grid_0_0">
        <Topology Dimensions="256 768 256" TopologyType="3DCoRectMesh"/>
        <Geometry Type="ORIGIN_DXDYDZ">
          <DataItem Dimensions="3" Format="XML">0.0 0.0 0.0</DataItem>
          <DataItem Dimensions="3" Format="XML">1.0 1.0 1.0</DataItem>
        </Geometry>
        <Attribute Name="fields/Density_e">
          <DataItem Dimensions="256 768 256" Format="HDF"
NumberType="Float" Precision="4">h5_0.h5:Density_e</DataItem>
        </Attribute>
      </Grid>
      <!-- .... -->
    </Grid>
  </Domain>
</Xdmf>

and the particles:

<Xdmf>
  <Domain>
    <Grid CollectionType="Temporal" GridType="Collection" Name="Polys">
      <Grid GridType="Uniform" Name="Poly_0_0">
        <Topology NodesPerElement="94109696" TopologyType="Polyvertex"/>
        <Attribute Name="particles/e/weighting">
          <DataItem Dimensions="94109696" Format="HDF"
NumberType="Float" Precision="4">h5_0.h5:weighting</DataItem>
        </Attribute>
        <Time TimeType="Single" Value="0"/>
        <Attribute AttributeType="Vector" Name="particles/e/momentum">
          <DataItem Dimensions="94109696 3" Function="JOIN($0,$1,$2)"
ItemType="Function">
            <DataItem Dimensions="94109696" Format="HDF"
NumberType="Float" Precision="4">h5_0.h5:momentum/x</DataItem>
            <DataItem Dimensions="94109696" Format="HDF"
NumberType="Float" Precision="4">h5_0.h5:momentum/y</DataItem>
            <DataItem Dimensions="94109696" Format="HDF"
NumberType="Float" Precision="4">h5_0.h5:momentum/z</DataItem>
          </DataItem>
        </Attribute>
      </Grid>
      <!-- .... -->
    </Grid>
  </Domain>
</Xdmf>


Best regards and thanks for your Feedback,
Axel Huebl

[1] http://picongpu.hzdr.de
-- 
.....................................................
. Axel Huebl               - Diploma Student        .
. a.huebl at hzdr.de          - Phone +49 351 260 3582 .
.            https://www.hzdr.de/crp                .
.                                                   .
. Computational Radiation Physics                   .
. Laser Particle Acceleration Division              .
. Helmholtz-Zentrum Dresden - Rossendorf e.V.       .
.                                                   .
. Bautzner Landstrasse 400, 01328 Dresden           .
. POB 510119, D-01314 Dresden                       .
. Vorstand: Prof. Dr.Dr.h.c. R. Sauerbrey           .
.           Prof. Dr.Dr.h.c. P. Joehnk              .
. VR 1693 beim Amtsgericht Dresden                  .
.....................................................





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