Comment (by Roland Haas):

That might be good, yes.

I am not sure if it really is a point further inward though. For the upper boundary (cctki0_idir > 0) the code sets ni = cctki0_imax-i which, for i close to the upper boundary, is actually a number close to 0. So it seems to me that it really gives magnitude of distance from the boundary such that the point on the boundary has distance +1 (since cctki_imax is exclusive).

I would also want to check two things before / when / very shortly after doing so:

• is there any code that (tries to) use(s) the ni as they are currently documented (there shouldn’t given that it would be quite horribly wrong)
• is there anything provided by the looping macros that does actually give information which boundary one is looping over (ie makes the ccti[012]_dir visible to the caller (which would also seem useful)

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2385/incorrect-normal-vector-when-looping-over