Issue Plotting USRBIN Output

Dear Fluka experts,

UPDATE - I believe the issue described below actually has to do with the number of points in the USRBIN which I defined. If I scroll up from the error messages which I showed in the screenshots below, Flair seems to complain about a dimensionality issue - the grid has too many points. My grid has 350^3 points. Is there a way to rebin the USRBIN output so that the array dimensions are not too large to be plotted? If so, how would I go about doing this? It would be nice to rebin the data I already have and not have to re-run the simulation.

I am having trouble plotting an output from my simulation. I tried to score neutrons in a region of interest. When I try to make a 2D heatmap with the .bnn output in Flair, I get this error.


I see that the error states “No usable data in this plot to autoscale axis range” and “All x points undefined”. Why would I get this type of error? I also scored neutrons using the USRBDX card in smaller regions and obtained sensible outputs. Please advise.

Thanks in advance for any insight,

Dear Dalini,

unfortunately it is not possible to change the binning of a finished simulation.

However it seems, you are using a FLUKA version, which is not supported on this Forum. We only provide help for the FLUKA and Flair versions releases by CERN at and

If the same issue happens with this version as well, please let us know.


Dear David,

Thanks for letting me know. You are right, it is not an issue with the CERN distro of FLUKA. I have the CERN distro on my personal work laptop and was able to verify that the array dimensions are not an issue to plot there. My institution uses the other distro, hence the reason why I originally ran into this issue.

I’ll make sure to check with my issues with the CERN distro before posting questions here.

Have a good day,