[MINC-users] from surface to adjacency

[EJ Nikelski]

Hi Pierre,

   I'm no expert on the structure of .obj files, but I believe that
one of the structures within the file is used to record the
correspondence between vertices and polygons.  Given that our our
cortical surfaces are constructed of triangles, this table has
number_of_polygons rows and 3 columns.  All 3 vertices for any
triangle would be adjacent, and the corresponding matrix rows-columns
could be set to 1.  Just loop over all triangles in the table, and you
should have the matrix that you're looking for.

HTH,

-Jim



On Fri, Mar 26, 2010 at 1:06 PM, Pierre Bellec
<pbellec at bic.mni.mcgill.ca> wrote:
> Dear minc users,
>
> I am currently trying to adapt a region-growing procedure for surface data.
> The procedure is using a representation of the adjacency matrix between
> vertices, i.e. a matrix (vertices times vertices) with 1s for pairs of
> vertices that are spatial neighbours on the surface, and 0 otherwise. I sort
> of understood that the order of the vertices in the obj file is very
> specific and follows an iterative refinement of the surface grid. Can anyone
> suggest an approach to generate the adjacency matrix based on the .obj data
> ?
>
> Thank you in advance,
>
> Pierre Bellec
> Post-doctoral fellow
> McConnel Brain Imaging Center, Webster 2B
> Montreal Neurological Institute
> 3801 University Street
> Montreal, Quebec, Canada H3A 2B4
> http://wiki.bic.mni.mcgill.ca/index.php/PierreBellec
> tel:       (001)(514) 398 5220
> fax:      (001)(514) 398 8948
> _______________________________________________
> MINC-users at bic.mni.mcgill.ca
> http://www.bic.mni.mcgill.ca/mailman/listinfo/minc-users
>



-- 
=================================
Jim Nikelski, Ph.D.
Postdoctoral Research Fellow
Bloomfield Centre for Research in Aging
Lady Davis Institute for Medical Research
Sir Mortimer B. Davis - Jewish General Hospital
McGill University