[Paraview] extracting irregular data

[Jan Valenta]

Hi all,

I need to extract data from one dataset based on data in another one. I
have two uniform rectilinear grids, one with velocity values the second
one with the ray coverage. I need to extract those data from the
velocity grid where the ray coverage exceeds certain value. I have tried
Append* and Extract* filters, but without any success. Probably mistake
on my side. Can you suggest anything, please? It surely have already
been solved in the list before, but I wasn't able to find the right
answer. 

Thanks to all,
Jan.