Hi Gari, The transformation actually consists of a 3 x 3 matrix and a 3 x 1 translation vector. The use of a 4 x 4 matrix allows the representation of an affine transformation as a matrix multiplication (http://en.wikipedia.org/wiki/Affine_transformation#Representation).
--Thomas On Wed, Sep 11, 2013 at 4:21 PM, Garikoitz Lerma-Usabiaga <gariko...@gmail.com> wrote: > Hi Doug, > just a very naive question about coordinate change: why do we need the > fourth component? I mean, shouldn't be the transformation matrix 3x3 instead > of 4x4 for a coordinate change in 3D space? > thanks! > Gari > > > On Wed, Sep 11, 2013 at 12:52 AM, Douglas N Greve > <gr...@nmr.mgh.harvard.edu> wrote: >> >> Hi Yang, I've computed a matrix that should do the trick. If you are in >> matlab, then >> >> M = [ 0.9975 -0.0073 0.0176 -0.0429 >> 0.0146 1.0009 -0.0024 1.5496 >> -0.0130 -0.0093 0.9971 1.1840 >> 0 0 0 1.0000] >> P305 = [MNI305x MNI305y MNI305z 1]'; >> P152 = M*P305 >> >> Can you give this a shot and see if it makes sense? It will probably be >> hard to tell since the matrix is pretty close to identity. >> >> doug >> >> >> >> >> On 09/10/2013 05:17 PM, Yang, Daniel wrote: >> > Thanks, Doug. I am really hoping to get MNI152 (because I also use >> > fsl). Are MNI305 and MNI152 the same? How can I obtain MNI152 >> > coordinates? >> > >> > Best, >> > Daniel >> > >> > -- >> > Yung-Jui "Daniel" Yang, PhD >> > Postdoctoral Researcher >> > Yale Child Study Center >> > New Haven, CT >> > (203) 737-5454 >> > >> > On 9/10/13 5:14 PM, "Douglas N Greve" <gr...@nmr.mgh.harvard.edu >> > <mailto:gr...@nmr.mgh.harvard.edu>> wrote: >> > >> > >> > It is an estimate of Tal coords from the MNI305. See >> > >> > http://imaging.mrc-cbu.cam.ac.uk/imaging/MniTalairach >> > >> > If you want MNI305, run mri_surfcluster with --nofixmni >> > >> > doug >> > >> > >> > >> > On 09/10/2013 05:08 PM, Yang, Daniel wrote: >> > >> > Hi all, >> > >> > The output of mri_surfcluster --sum shows TalX TalY TalZ. I am >> > wondering if they are based on the Talairach system or some >> > sort of >> > MNI-Talairach system. If the latter, can you tell me something >> > more >> > about it? Like a webpage that describes its relationship >> > between the >> > MNI152 or the Talairach system? >> > >> > I find it confusing because mri_surfcluster said: "INFO: >> > fixing MNI >> > talairach coordinates" >> > >> > Thanks! >> > Daniel >> > >> > -- >> > Yung-Jui "Daniel" Yang, PhD >> > Postdoctoral Researcher >> > Yale Child Study Center >> > New Haven, CT >> > (203) 737-5454 >> > >> > >> > _______________________________________________ >> > Freesurfer mailing list >> > Freesurfer@nmr.mgh.harvard.edu >> > <mailto:Freesurfer@nmr.mgh.harvard.edu> >> > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer >> > >> > >> > -- >> > Douglas N. Greve, Ph.D. >> > MGH-NMR Center >> > gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu> >> > Phone Number: 617-724-2358 >> > Fax: 617-726-7422 >> > >> > Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting >> > FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 >> > www.nmr.mgh.harvard.edu/facility/filedrop/index.html >> > Outgoing: >> > ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ >> > >> > _______________________________________________ >> > Freesurfer mailing list >> > Freesurfer@nmr.mgh.harvard.edu >> > <mailto: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. >> > >> > >> >> -- >> Douglas N. Greve, Ph.D. >> MGH-NMR Center >> gr...@nmr.mgh.harvard.edu >> Phone Number: 617-724-2358 >> Fax: 617-726-7422 >> >> Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting >> FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 >> www.nmr.mgh.harvard.edu/facility/filedrop/index.html >> Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ >> >> _______________________________________________ >> 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. > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
