Fast custom data output

Hi,

I want to output only the density at each point to very simple files (for later postprocessing), but my current try at simplifying the vtk output yields still too large files (and is far too slow).

Can you suggest a way to achieve faster data output?

My current try uses serializerToAsciiStream on a 512 x 512 x 512 lattice with 2 digits.

Can you give me a pointer, how to average over fixed size regions?

Best wishes,
Arne

PS: Where can I find the definition of the output of serializerToAsciiStream?