Matt has had two of his pull requests in the queue for a while. I think
both are very worthwhile changes that will unblock other work, so I'd like
to request some more pairs of eyes on them:
The first implements boolean objects, an oft-requested feature from yt 2.x.
The second makes it so our pixelization routines produce images via
compositing onto an existing image rather than returning an image which
does not exist yet. It also fixes some long-standing issues with the
orientation of images returned by the pixelizer.
The latter in particular will unblock work on supporting datasets that
contain multiple disjoint but continuous meshes - something that's common
in numerical relativity data.