[Paraview] particletracer, vectors menu?

[Charl Botha]

Dear all,

We are currently upgrading our Data Visualization lab from OpenDX to
ParaView. :)  (7 years ago, we made the step from AVS to OpenDX)

I have not been able to get the ParticleTracer going.  I'm
experimenting with the dataset Jean Favre makes available with his LEA
implementanion (I had to make a PVD for this, anybody want it?).  With
this dataset loaded, ParticleTracer remains greyed out.

In the documentation, it says: "This filter operates on any type of
data set, provided it has point-centered vectors."  What exactly does
this mean?  The LEA dataset has a "velocity" vectors component.  In a
single VTI timestep, it has:
<DataArray type="Float32" Name="velocity" NumberOfComponents="3"
format="appended" offset="0"/>

The calculator also seems to think of these as vectors.

What am I doing wrong?

Thanks for any advice,
Charl