[MINC-users] xfm2param -scale option does not do anything

[Andrew Janke]

Hi all,

> indeed.... param2xfm -scale 0.2 0.2 0.00001 test_scale_2D.xfm works though
>
> it might have something to do with the fact that affine transformation with
> scaling of zero is not invertible.

I'd say Vlad is right but on a quick look I can't see where this
happens.  My guess is that this is an artifact of the NR code (with
associated +1 indicies) in minctracc that does the transformations.
The multiplication of such things is done here:

   https://github.com/BIC-MNI/mni_autoreg/blob/master/minctracc/Numerical/matrix_basics.c#L810

>From when the affine matrix is built here:

   https://github.com/BIC-MNI/mni_autoreg/blob/master/minctracc/Numerical/make_rots.c#L236

I would argue that while this makes sense regarding generating an
invertible xfm for registration purposes it's not the entirely correct
answer. The resulting transformation should have been just on a plane
not the identity matrix. Seems that more investigation is needed on
this one.


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