That all sounds good. I've recently been moving markers around too, and I'm happy to send that script if you would like. There is 3dNwarpXYZ for coordinates that you could apply to tag coordinates. Provide an xyz.1D file with 3 columns of coordinates in RAI order (Right-to-left, Anterior-to-posterior, Inferior-to-superior).

3dNwarpXYZ -nwarp "$WARP" -iwarp ${src_name}_xyz.1D > ${src_name}_to_${target_name}_xyz.1D

As part of my script, I also put spheres at the source and target locations because I find that's useful for visualization, but the crosshair markers are fine too. Some examples of the spheres are here:
https://afni.nimh.nih.gov/pub/dist/doc/htmldoc/tutorials/rois_corr_vis/suma_spheres.html#description

3dTagalign requires the order match exactly. Labels are a convenience. The method works by finding a least squares solution. This information is excerpted from the source, thd_shear3d.c, DLSQ_affine() function:

Compute an affine transformation to take one set of vectors into another.
That is, find general matrix R and vector V so that

yy = [R] xx + V (k=0..n-1)
k k

is true in the unweighted least squares sense.



Edited 1 time(s). Last edit at 12/11/2021 05:01PM by Daniel Glen.