Hi, I want to get the vertex locations from a Surface SourceSpaces object. I’m not sure whether src[0][‘rr’] is what I need. Since MNE-Python uses Freeurfer surface RAS, is the result of src[0][‘rr’] in such coordinate frame? And is it possible to get the vertex positions in MRI scan RAS?
src[0]['rr'] is indeed in FreeSurfer surface RAS. To to convert to MRI scan RAS, you need to apply the inverse of the vox2ras transform to convert src[0]['rr'] to voxel indices, which you can then transform with the affine transform into MRI scan RAS.
I also find that MNE-Python offers another method to read the transform from subject’s RAS to MNI by mne.transforms.read_ras_mni_t. However, when I tried to apply this transform on subject’s RAS like: