Hi Martin,

Thanks for your quick response.

I think I am understanding you correctly.
For clarification...
Say, we have original points (x, y, z) in a given space and we'd like to transform it to a difference space:

x-translation: x' = x + p
                    y' = y
                    z'= z
y-translation: x' = x
                    y' =y +q
                    z'= z
x-translation: x' = x
                    y' = y
                    x' = x = r

Then:

affinematrix.png

 
The top left 3x3 submatrix in the last line above is equivalent to the left 3x3 submatrix of the matrix from talairach.xfm,
and the very right column in the matrix from talairach.xfm is equivalent to :
[p]
[q]
[r]

Am I understanding you correctly?

Thank you.


Best,
Lisa
______________________________
Lisa F. Akiyama
Research Study Assistant
Institute for Learning & Brain Sciences (I-LABS)
University of Washington
Portage Bay Building, BOX 357988
Seattle, WA 98195-7988  U.S.A.
E-mail: lrisa87@uw.edu

P Please consider the environment before printing this e-mail.



On Thu, Nov 4, 2010 at 11:09 AM, Martin Reuter <mreuter@nmr.mgh.harvard.edu> wrote:
Hi Lisa,

this is an affine transformation. Usually there is a 4th row containing
0 0 0 1

A point at position x,y,z is mapped to the target location via

M * (x,y,z,1)^t
where M is the 4x4 matrix and (x,y,z,1)^T is the column vector of the
coordinates of the point with a 1 in the 4th row.

The top left 3x3 sub matrix of M is a linear transformation
(rotation,scaling, sheering combined) and the last column is the
translation.

Take a look here to review
http://en.wikipedia.org/wiki/Transformation_matrix

So you cannot directly extract scaling factors and rotation from the 3x3
submatrix.

Best, Martin


On Thu, 2010-11-04 at 10:51 -0700, Lisa F. Akiyama wrote:
> Hello,
>
> Could someone inform me what each value of the 3x4 talairach
> transformation matrix signifies (e.g. translation, rotation in
> specific directions)?
> Here's an example of an talairach.xfm output.
>
>
>         MNI Transform File
>         % tkregister2
>
>         Transform_Type = Linear;
>         Linear_Transform =
>            1.05550623    0.03465762   -0.08214028   -3.92954969
>            0.02312534    1.03939676    0.38879746  -13.37033176
>            0.00010875   -0.35171938    1.10944259  -10.23139286
>
> Thank you.
>
>
> Best,
> Lisa
>  ______________________________
> Lisa F. Akiyama
> Research Study Assistant
> Institute for Learning & Brain Sciences (I-LABS)
> University of Washington
>
>
>
> P Please consider the environment before printing this e-mail.
>
>
>
> On Tue, Nov 2, 2010 at 2:59 PM, Lisa F. Akiyama <lrisa87@uw.edu>
> wrote:
>         Hello,
>
>         Are there any documentations on the details of the
>         talairach_avi command
>         and the 3x4 matrix (talairach.xfm) output?
>
>
>         Thank you.
>
>
>         Best,
>         Lisa Akiyama
>          ______________________________
>         Lisa F. Akiyama
>         Research Study Assistant
>         Institute for Learning & Brain Sciences (I-LABS)
>         University of Washington
>
>
>         P Please consider the environment before printing this e-mail.
>
>
>
>
> _______________________________________________
> Freesurfer mailing list
> Freesurfer@nmr.mgh.harvard.edu
> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer

_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer


The information in this e-mail is intended only for the person to whom it is
addressed. If you believe this e-mail was sent to you in error and the e-mail
contains patient information, please contact the Partners Compliance HelpLine at
http://www.partners.org/complianceline . If the e-mail was sent to you in error
but does not contain patient information, please contact the sender and properly
dispose of the e-mail.