<transform fileExtensions=".nrrd" type="nonlinear" reference="movingVolume">
<name>outputDisplacementFieldVolume</name>
<flag>O</flag>
<longflag deprecatedalias="output_field,outputDeformationFieldVolume">outputDisplacementFieldVolume</longflag>
<description>Output deformation field vector image (will have the same physical space as the fixedVolume).</description>
<label>Output Displacement Field Volume</label>
<channel>output</channel>
</transform>

================
This is a historical problem that I'll need more input in addressing. It is my understanding that Slicer does not handle displacement field transforms. Furthermore, ITKv3 did not formally handle them very well. The most "correct" thing to do is to make sure that BRAINSDemonsWarp is producing an ITKv4 compatible transform (i.e. a displacement field transform), and that Slicer learns how to deal with those.

There are several hacks that we could put into place, but I don't know which one is the least distastful:
1) Change this type to "image" rather than "transform" is probably the easiest stop gap.

DMeier, would you be able to test that?

Hans

This might have been fixed by recent nonlinear transform improvements.

@Dominik can you doublecheck?

@Alex please look into this and close the issue if it's resolved.

Andras, saving GridTransform node causes crash now (both as .nrrd or .tfm)
it's DisplacementGrid member is NULLL. Please take a look.

I confirm that latest nightly version Slicer crashes with the if you attempt to save an uninitialized grid transform (a node is created but not a displacement field image is not set). If you actually perform a demons registration and a field is computed then saving/loading of that field works well.

The fix for the crash (it logs a meaningful error message instead of crashing) is already available but not yet merged:
https://github.com/Slicer/Slicer/pull/132

Alex can you look at the pull request? If it looks good you can merge it to svn using the instructions here:

http://www.slicer.org/slicerWiki/index.php/Slicer:git-svn#Integrating_topic_from_external_contributor

The note on the crash:
I run demons with default parameters on fixed.nrrd in moving.nrrd located in Libs/MRML/Core/Testing/TestData

The CLI completes and I don't see errors reported. However Slicer crashes on save with null DeformationField (which I understand Andras has fixed). Still I would expect to see an error reported from CLI if it cannot create a valid Grid transform. I don't know if the problem is in Demons CLI or slicer.

Having said this, the code looks reasonable, so I suggest Andras merges it into trunk.

Resolution merged into trunk:
http://viewvc.slicer.org/viewvc.cgi/Slicer4?view=revision&amp;revision=23185

Closing resolved issues that have not been updated in more than 3 months.