Hi Pierre,

I ended up writing a small script to do this. To anyone else who may need to read in displacement fields, the way I did it was to extract each vector component from the displacement field and read it in separately as a 3D volume. Depending on what registration algo is used, the "vector dimension" bit may have to be swapped (I seem to recall that demons and minctracc give fields with different fastest-varying dimensions). Something like this:

---

function [grid] = read_grid(grid_name)

% get 3 components of displacement field
command = ['mincreshape -clobber -dimrange vector_dimension=1,0 ' grid_name ' x_comp.mnc']; system(command);
command = ['mincreshape -clobber -dimrange vector_dimension=0,0 ' grid_name ' y_comp.mnc']; system(command);
command = ['mincreshape -clobber -dimrange vector_dimension=2,0 ' grid_name ' z_comp.mnc']; system(command);

% read each file with niak
[~,v] = niak_read_minc('x_comp.mnc'); grid(:,:,:,1) = v;
[~,v] = niak_read_minc('y_comp.mnc'); grid(:,:,:,2) = v;
[~,v] = niak_read_minc('z_comp.mnc'); grid(:,:,:,3) = v;

end