In the spirit of solving problems immediately after asking for help, I just rediscovered Matt and Cameron's tool for doing precisely what I need:

https://bitbucket.org/chummels/yt.lagrangian_volume

Thanks anyway, folks.  :-D



On Sat, Aug 9, 2014 at 10:34 AM, Brian O'Shea <bwoshea@gmail.com> wrote:
Hi folks,

I'm going back to resimulate some cosmological simulations with a nested-grid setup, and can't seem to figure out how to get yt to tell me where all of the dark matter particles in a given halo start out at high redshift.  It seems that something like this used to exist in the Hub (i.e., http://lists.spacepope.org/pipermail/yt-users-spacepope.org/2011-August/001879.html), but that is not around any more.  Would somebody mind sharing such a tool if they have already coded it up?

Thanks!

--Brian