Dear Jeff and All,
>Unfortunately this doesn't have an easy answer as it depends
>on certain conventions, such as where you want the centre
>of rotation to be. In fact, all the elements in the 3x3 submatrix
>are affected by rotations, and the centre of rotation plus the
>rotations themselves plus the desired translations affect the
>elements in the fourth column.
If you wish to get a better sense of the matrix math behind the
creation of the HTM, you might refer to:
http://godzilla.kennedykrieger.org/~bettyann/msThesis/ms090_appa/ms090_appa.html
However, as Mark mentions, the resulting HTM depends upon
conventions. Hopefully the above link will give you a sense of
why this question has a tricky answer.
Best,
- BettyAnn
>If you want a decomposition using _our_ conventions, then
>run avscale --allparams on the matrix file and it will give you
>the rotations, translations (with respect to the centre of rotation
>being the lower left corner of the image) plus scales and skews.
>
>If you want to go the other way, you can create 6 dof matrices
>using the makerot utility.
>
>Hope this helps.
>All the best,
> Mark
>
>
>
>On 27 Sep 2006, at 19:25, Jeffrey Stanley wrote:
>
>> Dear FSLer's ... I need help in the definition of the terms in the
>> 4x4 transformation matrix (a.k.a.,
>> the *.mat file) ... from what I can tell the M14, M24 and M34
>> elements are the x, y,z translation
>> terms... M11, M22 and M33 elements are the respective scaling
>> terms... however, which elements
>> control the rotation and what are the unites... for example, what
>> would the elements be if I wanted
>> to rotate the image about the x-axis by 30 degrees???
>>
>> any help is greatly appreciated.
>>
>> Jeff
>>
>>
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