Hi. I am going to need a sample of points distributed equally over the cortical surface, with a given spacing between them.
I noticed that freesurfer has the capability to do this, but I am wondering HOW it is done, to see if indeed it does what I expect. (tools - decimate)
In particular, I would like a "surface distance" measure of the spacing, not a 3D euclidean distance as a measure of the spacing, or some other measure.
I did a little test, and it was strange. I decimated with a distance of 6, and with 10. I then asked matlab to find the minimum distance between vertices for all vertices in the decimated set, and got mean and median values of those.
Here is the weird part. For the spacing of "6", the mean and median of the minimum distances were 8 and 9 or so. For the spacing of "10", the mean and median of the min distances were 15 and 13.
Realizing that my technique of getting the minimum euclidean distance is WRONG, but it should provide a simple approximation. That is, my measure should be SMALLER than the surface distance measure. Therefore, it doesn't make sense to me that the decimation is doing what I was hoping it does, because for surface spacings of 6, I expect euclidean distances to be less than 6, and for surface spacings of 10, I expect euclidean distances to be less than 10.
Thoughts from freesurfing fellows?