methoed to do this which is both fast and foolproof

between fsl.transform.nonlinear and fsl.data.image.

winding order, to account for the possibility that different vertex sets
require different orders.

check data shape, and raise if bad.

used

the vertex set changes.

file path for vertex data key.

deprecation warning on access though.

method to query current vertex set.

incorrectly

trimesh ray.intersect_id function.

convinced that this is foolproof, but it seems to work.