Greetings,
Just a note -- in revision 719 -- I've committed a fix for the GUI
component (reason) that was causing huge and inappropriate delays to
projecting a dataset, if that dataset had more than about 10,000
grids. The GUI was updating every time a new grid was masked and
examined, which was oftentimes many times more than once per second.
It should be working now. Fixes have been committed to both trunk/
and branches/yt-1.0 .
-Matt