[Yt-dev] field_parameters in phase plots

[david collins]

Hi, Matt/everyone--

I'm trying to make a density/magnetic field/ mean velocity dispersion
plot, where the velocity is the z (color) axis.

I want my dispersion to be V-BulkVelocity, but right now I'm getting
BulkVelocity through set_field_paremter, which seems to not be done on
the extracted regions inside of the phase plot.  Anyone have a good
idea how to feed BulkVelocity automatically in to the quantity?

d.