Hi, Ziad,
Thanks very much. Not sure that I completely get it. Here's what I was thinking (maybe this will help you to steer me in the right direction):

(1) I'll use CreateIcosahedron to generate a spherical surface.

(2) In MatLab I'll create volumes encompassing the sphere, each with a different vector projected onto the surface of the sphere. I.e. each volume would have zeros everywhere, and ones where the vector intersects the unit sphere.

(3) Save these volumes to BRIK files using WriteBrick.

(4) Load the sphere into SUMA.

(5) Start AFNI. Set the volumetric version of the sphere surface as the underlay (not sure how to generate this). Step through the volumes that I created in (3) as the overlays. Take a snapshot of each in SUMA and use these snapshots to create a movie.

This may not be the easiest way to do it. In what you suggested it sounds like I don't use AFNI at all. I don't know how to step through different overlays in SUMA (without having it talking to AFNI), but maybe this is easy. Is ConvertSurface a MatLab function or do you run it from the shell? If I generate the overlay surfaces directly in MatLab (a) how do I specify them in MatLab (I was just going to use a volume, as I am pretty naive when it comes to surfaces), and (b) how do I save them?

Thanks,
Aaron