Hi,
I can see that these things are not as well described as they could be.
The matrix files from mcflirt, or any FSL tool, use the bottom left corner for the centre of rotations.
The par file from mcflirt uses the centre of gravity for the centre of rotation.
So, in a way, both are right.
I've modified the wiki page to hopefully make it a bit clearer.
All the best,
Mark
On 8 May 2014, at 16:16, Joerg Pfannmoeller <[log in to unmask]> wrote:
> Hello,
>
> I am trying to compute motion parameters for a Possum simulation. Therefore I use MCFlirt to extract motion parameters from an epi-scan done at our scanner. After that I use the matlab script given in the web to compute the motion parameter file for Possum (see www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind1208&L=FSL&P=R43854&1=FSL&9=A&J=on&d=No+Match%3BMatch%3BMatches&z=4). The author of the script claims:
>
> "the centre of rotation in Possum is the centre of the input volume object (half length in x,y,z) and the centre of rotation in McFlirt is the centre of gravity of the reference image (you can obtain this with fslstats <reference image> -c )".
>
>
> While the official fsl Possum page claims:
>
> "center of rotations for the mcflirt motion file is in the bottom left corner of the object and for the POSSUM motion file is in the center of the object".
>
> Which one is right?
>
> Sincerely yours pfannmoe
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