Hey, I've previously been able to make off-axis projections of ramses datasets with geometric data containers. However, I've recently tried to do this with a cut_region for dens gas, without success. Here is a script that should work with a ramses cosmo dataset: import yt import numpy as np num = 1 Look = [1.,1.,0] Up = [0.,1.,1.] c = np.array([0.5,0.5,0.5]) rad = 0.2 width = 2*rad extra = 1.05 left = c - rad*extra right = c + rad*extra bb = [left,right] fn = "../output_{0:05d}/info_{0:05d}.txt" ds = yt.load(fn.format(num),bbox=bb) region = ds.region(c,left,right) d20 = region.cut_region(['obj["density"] > 1e-20']) p1 = yt.OffAxisProjectionPlot(ds,Look,"density", weight_field='density',center=c,width=width,data_source=region,north_vector=Up) p1.save("OAProjDens_Region_{0:03d}.png".format(nout)) p1 = yt.OffAxisProjectionPlot(ds,Look,"density", weight_field='density',center=c,width=width,data_source=d20,north_vector=Up) p1.save("OAProjDens_D20_{0:03d}.png".format(nout)) The first OA Projection is generated correctly, but the second one crashes with the message: yt : [INFO ] 2018-02-12 22:20:08,915 Making a fixed resolution buffer of (('gas', 'density')) 800 by 800 yt : [INFO ] 2018-02-12 22:22:05,737 Saving plot OAProjDens_Region_001.png yt : [INFO ] 2018-02-12 22:22:06,641 xlim = -0.2 0.2 yt : [INFO ] 2018-02-12 22:22:06,641 ylim = -0.2 0.2 yt : [INFO ] 2018-02-12 22:22:06,641 zlim = -0.500000 0.500000 yt : [INFO ] 2018-02-12 22:23:58,431 Making a fixed resolution buffer of (('gas', 'density')) 800 by 800 Traceback (most recent call last): File "MakeOffAxisProjClouds.py", line 176, in <module> p1 = yt.OffAxisProjectionPlot(ds,Look,"density", weight_field='density',center=c,width=width,data_source=d20,north_vector=Up) File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/plot_window.py", line 1727, in __init__ fontsize=fontsize) File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/plot_window.py", line 660, in __init__ PlotWindow.__init__(self, *args, **kwargs) File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/plot_window.py", line 219, in __init__ self._setup_plots() File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/plot_window.py", line 748, in _setup_plots self._recreate_frb() File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/plot_window.py", line 1733, in _recreate_frb super(OffAxisProjectionPlot, self)._recreate_frb() File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/plot_window.py", line 272, in _recreate_frb self._frb._get_data_source_fields() File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/fixed_resolution.py", line 155, in _get_data_source_fields self[f] File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/fixed_resolution.py", line 543, in __getitem__ method=dd.method) File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/visualization/volume_rendering/off_axis_projection.py", line 189, in off_axis_projection for i, (grid, mask) in enumerate(data_source.blocks): File "/mnt/blackwhale/home/mrichard/soft/yt/yt_cphyc/yt/data_objects/selection_data_containers.py", line 836, in blocks with obj._field_parameter_state(self.field_parameters): AttributeError: 'OctreeSubsetBlockSlicePosition' object has no attribute '_field_parameter_state' I'm trying to find how to have d20 inherit _field_parameter_state from region, but thought someone might be able to point me in the right direction a bit faster. Thanks! -Mark -- Mark Richardson MAT Postdoctoral Fellow Department of Astrophysics American Museum of Natural History Mark.Richardson.Work@gmail.com My Website <https://sites.google.com/site/marklarichardson/> 212 496 3432