Hi I think I've found a bug with serialization and projections with a data_source. If I do a projection providing a data_source everything is fine: disk = pf.h.disk((0.5,0.5,0.5), (0,0,1), (10.0,'kpc'), (2.0,'kpc')) pc = PlotCollection(pf) pc.add_projection("NumberDensity","z",weight_field="Density", data_source=disk) But then, if I do the exact same projection without a data_source, it breaks with an error: 'No field named px'. The full traceback is at http://paste.yt-project.org/show/2637/. Note that if I first delete the .yt file, then the projection without data_source works just fine. Mike -- ********************************************************************* * * * Dr. Michael Kuhlen Theoretical Astrophysics Center * * email: mqk@astro.berkeley.edu UC Berkeley * * cell phone: (831) 588-1468 B-116 Hearst Field Annex # 3411 * * skype username: mikekuhlen Berkeley, CA 94720 * * * *********************************************************************