Folks:
I'm trying to use 3dVol2Surf with a FreeSurfer subject's data, and have the following problem:

1. Based on the -map_func description, presumably 3dVol2Surf expects two surfaces... yet the spec file describes four surfaces... how does 3dVol2Surf know which two to use?

2. Overlooking item 1, if we run 3dVol2Surf, it shows messages like:
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Surface #0/4 (directly mappable), loading...
Surface #1/4 (mappable via MappingRef), loading...
Surface #2/4 (mappable via MappingRef), loading...
Surface #3/4 (mappable via MappingRef), loading...
Found 1 mappable surfaces (but expected 2)
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What does this all mean? It reports that all 4 surfaces are mappable, but then claims only one is.
If this means that it can only use the first *directly* mappable surface for comparing vertex position to voxel value, then that's a further problem, since the first surface is the smoothwm surface, which is not very relevant... we want it to use the vertices of the pial and white surfaces.

Bottom line, obviously a gap in our understanding of how the spec file and the surface loading works.

Thanks,
Graham