[Paraview] How to calc the mass-flow-rate of a pointset

[Christian Richter]

Hello all,

I want to calc the mass-flow rate of a Pointset containing the positions 
and velocities. I read the HowTo's google showed me, but they all uses 
vector fields.
Is there a filter to calculate the mass-flow rate of moving particles ? 
I tried calculator[coords z] -> Integrate Variables->Surface flow but 
it's always 0.

Thanks,
C. Richter