Hey Z,

Note that Daniel has temporarily fled the country, so he might not reply until we can drag him back.

My ignorant take on this is that the NL transform would not need to be recomputed. But it is not the forward F:A->B transform that you could extract the xyz offsets from, but the inverse F^-1:B->A one (and then take the inverse (negatives) of those offsets).

The point is that the offset columns of F (in the forward direction) are essentially applied AFTER the rotational pieces. So in order to use 3drefit, you would have to rewrite F as a shift transform followed by the rotational one. That might mean computing F inverse, separating it as rotation and shift matrices, and then inverting those pieces. cat_matvec could probably be used for that.

Does that seem reasonable?

- rick