This code is taken from InsightApplications-1.4.0/MultiResMIRegistration.
The input file is exactly the same as the one from there, so read the
directions for the input there. Or, see below.

Alas, most of the input is ignored.  Only the first file is read in. A
transform is applied to it.  Then, we see if the Registrator can
capture that transform. That is the test

An example input file is in this directory. It is called ExampleInputFile.

The first critical parts is the volume to be read in:
/projects/test/rotz/tt-rot-z
1
256 256 60
0.9375 0.9375 2.5

The second critical part is below:
5                                # The number of multi-res levels
4 4 1                            # The down-sampling of the first volume
4 4 1                            # The down-sampling of the second volume
2500 2500 2500 2500 2500         # The number of iterations at each level
1e-4 1e-5 5e-6 1e-6 5e-7         # The step multiplier for grad descent
320                              # The translation scale factor