I'm testing out vecreg. I have a nifti with dimension x,y,z,3 which stores vectors at each voxel. As a test I created a .mat file with:
[1 0 0 0;
0 1 0 0;
0 0 1 0;
0 0 0 1]
When I apply vecreg with:
vecreg -r vec.nii -i vec.nii -t xform.mat -o vec_reg.nii.gz
The vectors are actually completely flipped. i.e. voxels that had a vector of (0.4,0.5,0.6) after vecreg are now (-0.4,-0.5,-0.6). For my purposes this complete flipping actually won't matter, but is there an reason for this behavior? Or is it a cause for concern? It would be nice for this not to occur.
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