[MINC-users] xfmavg and lsq6 transforms

[Gabriel A. Devenyi]

Sure, easiest to expose with xfm2param:

#One of 32 transforms
> xfm2param input1.xfm
after parameter extraction
-center         0.00000    0.00000    0.00000
-translation    0.70513    0.30790    0.66079
-rotation     -87.58608    4.54388    2.03792
-scale          1.00000    1.00000    1.00000
-shear         -0.00000   -0.00000    0.00000

#Transforms have rotations in range 83-92 -6-7 -2 4
> xfmavg *.xfm average.xfm
> xfm2param average.xfm
after parameter extraction
-center         0.00000    0.00000    0.00000
-translation    0.38288    0.50712    0.52295
-rotation      -0.04862    0.66666   -0.63100
-scale          1.00000    1.00000    1.00000
-shear         -0.00000   -0.00000    0.00000

#Rotations have been completely lost

I just realized this may be due to the values since they’re near -90, could
this be a problem?
​

-- 
Gabriel A. Devenyi B.Eng. Ph.D.
Research Computing Associate
Computational Brain Anatomy Laboratory
Cerebral Imaging Center
Douglas Mental Health University Institute
McGill University
t: 514.761.6131x4781
e: gdevenyi at gmail.com

On Thu, Feb 11, 2016 at 10:25 AM, Vladimir S. FONOV <
vladimir.fonov at gmail.com> wrote:

> What were your expectations and what did you get?
>
> On Thu, Feb 11, 2016 at 9:53 AM, Gabriel A. Devenyi <gdevenyi at gmail.com>
> wrote:
>
> > Hi minc-users,
> >
> > I have successfully used xfmavg on lsq12 transforms numerous times with
> no
> > issues (and it runs great with pydpiper).
> >
> > I recently tried to average some (very similar) lsq6 transforms and found
> > that the result is not at all what I expected, it is quite far off from
> the
> > inputs.
> >
> > Do lsq6 transforms not satisfy the mathematical underpinnings of xfmavg
> or
> > is something else going on?
> >
> > Thanks for your insight!
> >
> > --
> > Gabriel A. Devenyi B.Eng. Ph.D.
> > Research Computing Associate
> > Computational Brain Anatomy Laboratory
> > Cerebral Imaging Center
> > Douglas Mental Health University Institute
> > McGill University
> > t: 514.761.6131x4781
> > e: gdevenyi at gmail.com
> > _______________________________________________
> > MINC-users at bic.mni.mcgill.ca
> > http://www.bic.mni.mcgill.ca/mailman/listinfo/minc-users
> >
>
>
>
> --
> Best regards,
>
>  Vladimir S. Fonov ~ vladimir <dot> fonov <at> gmail <dot> com
> _______________________________________________
> MINC-users at bic.mni.mcgill.ca
> http://www.bic.mni.mcgill.ca/mailman/listinfo/minc-users
>