Dear Jeff,
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 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
>
>
|