[caret-users] Re: Surface Normals

Alon Keren alonker at gmail.com
Sun Jun 10 10:22:41 CDT 2007


John,

Thanks for the prompt and elaborated reply.
It was very helpful.

Alon.


On 6/6/07, John Harwell <john at brainvis.wustl.edu> wrote:
>
> Alon,
>
> The surface normals are not stored in a file.  For each coordinate
> file that is loaded into Caret, the normals are computed using the
> coordinates and the topology file associated with the coordinate file.
>
> Normals are computed as follows:
> * Compute the normal vector for each triangle in the surface
> * For each node, assign it a normal vector that is the average of the
> normal vectors of the triangles that use the node
> * Convert each node's normal to a unit vector (length equals 1.0)
>
> If you want to see the values of the normal vectors, use File Menu-
> >Export File and write a surface as either a VTK surface file or a
> VRML file.  Both of these files include coordinates, surface normals,
> and topology.  Simply search one of these files for the characters
> "Normal".
>
> ----------------------------------------------------------
> John Harwell
> john at brainvis.wustl.edu
> 314-362-3467
>
> Department of Anatomy and Neurobiology
> Washington University School of Medicine
> 660 S. Euclid Ave.    Box 8108
> St. Louis, MO 63110   USA
>
> On Jun 6, 2007, at 5:31 AM, Alon Keren wrote:
>
> > Hello,
> >
> > I would like to extract from CARET a list of normals to the
> > cortical surface at each node. I saw that CARET can show these
> > normals (Display Control window --> Page Selection list --> Surface
> > Miscellaneous --> Show Normals checkbox). Are these data stored in
> > a specific file, or are the normals computed from the topography
> > file? Where are they stored or how are they computed?
> >
> > Thanks,
> > Alon.
> >
> >
> >
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> > caret-users at brainvis.wustl.edu
> > http://pulvinar.wustl.edu/mailman/listinfo/caret-users
>
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