Hi Bruce,

Thanks for the response. I've run the operation and have examined the output. From my understanding the file contains both a vertex list (XYZ) and a face list containing (V1,V2,V3...). Is the XYZ of the vertex list the actual surfaceRAS coordinates of the surface as viewed on FreeViewer? If so I can compute face normals simply by matching up the 3 vertices encapsulating the given surface coordinate and computing the face normal vector, correct?

Thanks again

Jerry

From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of Bruce Fischl <fischl@nmr.mgh.harvard.edu>
Sent: May 8, 2017 4:40:17 PM
To: Freesurfer support list
Subject: Re: [Freesurfer] Obtaining surface normal vector from plial surfaceRAS coordinate
 
Hi Jerry

mris_convert -n lh.pial lh.pial.normals.asc

should create a list of surface normals in ascii format

cheers
Bruce
On Mon, 8 May 2017,
Jerry
Jeyachandra wrote:

>
> Hi list,
>
> I¢d like to extract the surface normal at a location specified in surfaceRAS
> coordinates after performing segmentation. I know there are methods to
> extract all vertices and faces then compute face normals from there, but I¢m
> not familiar with methods to relate these to specified coordinates.
>
> Thanks
>
> Jerry Jeyachandra
>
>
>