compute sulcal depth

[alexhuth]

We should be able to compute sulcal depth from the surfaces without relying on freesurfer. This is the only surface property that we are still relying on freesurfer for.

[alexhuth]

Ugh freesurfer computes it based on the inflation process, that's not gonna work for us. But we can compute a reasonable facsimile just by taking the distance to the convex hull. This is ridiculously simple, and looks pretty good:

import scipy.spatial
import cortex
pts, polys = cortex.db.surfs.getSurf("S1", "fiducial", "left")
lsurf = cortex.polyutils.Surface(pts, polys)

# Find convex hull
lsurf_tess = scipy.spatial.Delaunay(lsurf.pts)
lsurf_hullpts = np.unique(lsurf_tess.convex_hull)

# Find euclidean distance from each vertex to closest vertex in convex hull
kdt = scipy.spatial.cKDTree(lsurf.pts[lsurf_hullpts])
dist,idx = kdt.query(lsurf.pts)