-------------------------------------------
 The SubjectTools -> WM Filter (hi-res) starts a
 background process to generate anisotropically
 filtered images of the white matter
-------------------------------------------
A 5x5x5 anisotropic "plane filter" is moved pixel
by pixel through the input volume.  At each
pixel, a geodesic set of directions are searched
to find the set of parallel planes in which the
variance in brightness is minimized.  This is a
rough estimate of the local tangent plane to the
cortex.

A median filter is then applied within each plane
to eliminate spiky artifacts.

The resulting data set is then thresholded to
zero below the "white low limit" and above the
"white high limit".

The preferred input is the "brain" data set but
"T1" and finally "orig" are tried in that order
if "brain" is not found:

 input3D: $SUBJECTS_DIR/$name/mri/brain[.mgz]
    or, if above not found:
 input3D: $SUBJECTS_DIR/$name/mri/T1[.mgz]
    or, if above not found:
 input3D: $SUBJECTS_DIR/$name/mri/orig[.mgz]

 output3D: $SUBJECTS_DIR/$name/mri/wm[.mgz]

Regions That May Need Manual Edits

By its design, this filter will tend to
over-erode the attachment point of a thin
perpendicular sheet to a flat plane.

One such region (viewed in the CORONAL plane) is
the thin white matter sheet just under the
hippocampus that connects entorhinal cortex with
the main body of white matter in the temporal
lobe.

This program is multi-threaded to run faster by
using all available cores (8 threads).
