Hi Jidan,

we actually do further inflation now to remove convexity, then only do the projection once most convexities in the surface are removed. At that point I believe we use the mean of the [xyz] min and max of the surface as the center of the sphere.

cheers, Bruce

On Thu, 13 Aug 2009, Zhong Jidan wrote:

Hi Freesurfer experts,

I have a question about the sphere transformation from the inflated surface. In the paper "cortical surface-based analysis II", you mentioned that each vertex is put in a normal vector field which is from the center of the sphere to the vertex, then you project the inflated surface onto a unit sphere. The question is, how do you choose the center of the sphere? If you choose a different location as the center of the sphere, the new sphere you get will be different. So how do you make sure that the center you choose is the one you want?

Thanks a lot.