Workbench Command is a set of command-line tools that can be used to perform simple and complex operations within Connectome Workbench.
CALCULATE VOLUME WARPFIELD DISTORTION
wb_command -volume-distortion
<warpfield> - the warpfield to compute the distortion of
<volume-out> - output - the output distortion measures
[-fnirt] - MUST be used if using a fnirt warpfield
<source-volume> - the source volume used when generating the warpfield
[-circular] - use the circle-based formula for the anisotropic measure
[-log2] - apply base-2 log transform
Calculates isotropic and anisotropic distortions in the volume warpfield.
At each voxel, the gradient of the absolute warpfield is computed to
obtain the local affine transforms for each voxel (jacobian matrices),
and strain tensors are derived from them. The isotropic component
(volumetric expansion ratio) is the product of the three principal
strains. The default measure ('elongation') for the anisotropic
component is the largest principal strain divided by the smallest.
The -circular option instead calculates the anisotropic component by
transforming the principal strains into log space, considering them as
x-values of points on a circle 120 degrees apart, finds the circle's
diameter, and transforms that back to a ratio.