[yt-dev] field line tracing problems

Hi All (especially Sam), I'm trying to understand some behavior in the streamlines that I don't completely understand. I've documented the problem in a notebook here: https://hub.yt-project.org/nb/2tmwor The notebook has a full statement of the problem. In essense, I'm not sure I understand why streams that I believe should terminate instantly upon launch (because they should walk directly out of the box) have thousands of elements in them (instead of one). I assume there are one or more misconceptions in my understanding, and I'd really welcome any suggestions. thanks, Jeff