[yt-users] 3D physical properties from projection plot

Hi All, I'm trying to calculate some physical properties from a gadget data set on a similar grid as projection plot, but in 3D. That is, if I calculate a projection plot:

px_gas = yt.ProjectionPlot(ds,"z",("gas","density")) px_gas_frb = px_gas.frb

then I can access the gas surface density values in some 800x800 (or whatever) 2D array. What I would like is to be able to get the gas physical properties in the 800x800x800 (or whatever) grid that yt is integrating along to give me the Projection Plot (in particular the gas mass, and the gas velocity vectors). Is this possible? Thanks a lot, -d