The effect of checking "advanced" (an observation)

[N-Dekker]

When a user checks "advanced", various elastix registration parameter values may be changed, even when the user leaves them at their default state:

• The "bspline" preset has metric values ("AdvancedMattesMutualInformation", "TransformBendingEnergyPenalty"), whereas "advanced" just uses "AdvancedMattesMutualInformation".
• All non-custom presets have "MaximumNumberOfIterations" value 256, whereas the "advanced" has max_iterations = 500.
• All non-custom presets have "NumberOfSpatialSamples" value 2048, whereas the "advanced" has nr_spatial_samples = 512.
• For a non-custom preset, AdaptiveStochasticGradientDescent may automatically estimate its MaximumStepLength, whereas the "advanced" has max_step_length = 1.0.

Luckily, the number of resolutions ("NumberOfResolutions") is the same (value 4), for both "advanced" and non-advanced non-custom presets.

This is just an observation, but maybe we need to make this clearer somehow...

• I did already mentioned this at pull request ENH: Add use_corresponding_points function parameter + widget #57

[N-Dekker]

To consider:

• Make MaximumNumberOfIterations = 500 the default, for any preset
• Use spatial_samples = 2048 for advances as well
• Drop "TransformBendingEnergyPenalty" from preset (check with Stefan).
• Allow adjusting MaximumStepLengthRatio (default 1.0), instead of MaximumStepLength