If you import a Freesurfer surface into Caret, it won't align with the volume 
in mri/orig.mgz until you apply an offset transformation defined by something 
like mri_info -cras (I forget the exact command).  Depending on which surface 
you apply that transformation -- before or after cras offset -- you could get 
the behavior you describe.


On Dec 24, 2012, at 7:51 PM, Colin Reveley wrote:

> Hey, merry christmas.
> 
> I have a surface. and a volume. they are in register in caret. the volume has 
> an origin reported in the nifti header.
> 
> If I apply a rigid body transform to both, they are both rotated the way I 
> want (the way I want is so that the surface, and MR data in the slice plane 
> as some microscope slides of the sample) but the surface is no longer in 
> register with the volume. 
> 
> the rotations are right. but the translations aren't (there aren't any 
> translations intended actually)
> 
> I can 
> 
> a) manually translate the surface around in caret till it roughly fits (which 
> I did, it's fine for now)
> b) adjust the origin of the nifti (the origin isn't changed by applying the 
> transform with flirt)
> 
> or I guess c) adjust something in the surface header. couldn't see what.
> 
> It occurred to me to treat the original volume origin as a vector and apply 
> the transform to it, then set the origin of the rotated volume to those 
> values.
> 
> Probably that would work. But it's a bit too much linear algebra for me.
> 
> Moving on from the obvious fact that I'm not that bright, surely doing 
> exactly this kind of thing ought to be pretty easy?
> 
> 
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