Your 2nd description is correct. Note that the value of vertices outside of the mask are NOT changed (ie, they are not set to 0).
doug
DRC SPM wrote:
Dear FreeSurfers,
Please can you explain how mri_surf2surf's --cortex option for smoothing is implemented?
I assumed it would be along the following lines:
- mask the data to zero-out the medial wall
- smooth this masked data
- smooth the mask itself
- divide the smoothed data by the smoothed mask
- (perhaps) re-mask the data
But I've tried doing that long-hand (i.e. calling mri_surf2surf without the --cortex flag for each smoothing, and using l load_mgh and save_mgh in MATLAB for the rest), and it doesn't seem to quite match the results of the --cortex flag.
Now I'm guessing that it instead might do something like the following. For each connected-neighbour iteration of the smoothing, only include the neighbour in the average if it is inside the cortex (not medial wall). However, I can't easily/lazily reimplement this to check, so could someone reveal the truth? ;-)
Many thanks, Ged _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer