[Freesurfer] converting vertex numbers in .label files to R, A, S coordinates

Dear Freesurfer experts,

My question concerns the .label files and the correspondence between the vertex numbers (in the first column) and the R,A,S coordinates.

I have the R,A,S coordinates of voxels that I want to display on the surface. For this purpose, I created a label file with the R,A,S coordinates (col 2,3,4) and random vertex ID in the col 1 (since I do not know what is the vertex ID for a given R,A,S coordinate). I displayed the content of the label file via tksurfer. However, tksurfer reads vertex ID, not R,A,S coordinates.

I wonder whether anyone knows about a function computing the vertex ID based on the R,A,S coordinates, or an alternative solution to represent the vertices on the surface based on the voxel coordinates--and the registration file I assume?

Thank you very much!

Best Li Guo & Florence Campana

Thanks a lot!