Hi Axel,

I could do a Google hangout or something on Friday. In the meantime, I agree with Nathan that it looks like some particle fields that are supposed to be set up automatically aren't getting created for some reason, but it's hard to say exactly what's going wrong. If you can reproduce this problem on a public dataset I could download, I'd be happy to take a look. 

On Tue, May 24, 2016 at 9:30 AM, Huebl, Axel <a.huebl@hzdr.de> wrote:
Hi yt-devs,

I am forwarding this conversation to the public list to keep it open for
others to join in and to build up a record that might help others.

Our new student Fabian updated our frontend and implemented particle
readers. Unfortunately some details of the particle "fields" still cause
some bumps that we can not get our head around.

We are now able to read fields and particles, even chunk-wise, and can
work with the data we read in python scripts via the all_data() method.

Nevertheless, using the particle scatter plots such as yt.ParticlePlot
seems not to work. We have some problems with unions / the "all" group
and the fact that we have several particle species (e.g., "hot
electrons", "cold electrons", "helium ions", "nitrogen ions", etc.)

Also since the last rebase: did someone recently change the unit system
in yt? T for "Tesla" seems not to be understood any more. Is there a
changelog somewhere available? Do we have to describe our data in cgs / mks?

Would someone be interested for a quick heads up via e.g., skype /
web-rtc so we can ask specific questions?

Fabian is around on Tuesdays and Fridays, something like early CA time,
and late GER time usually works great (e.g., 9pm-PDT / 6pm-CEST).

Our current branch HEAD can be found here (->yt->frontends->openPMD):

And an example script is attached.

Thanks a lot!