Hi Marc,

Transformation matrices T(x) are generally considered to
be applied as T*x, though there are some who prefer it
the other way.  NIFTI (and therefore GIFTI) apply it in that
common way, as specified in the NIFTI standard.

The most detailed description of the NIFTI standard is in
the nifti1.h header file, here:

    nifti.nimh.nih.gov

Search for either "Method 2" or "Method 3", though the
latter is more appropriate, as it applies directly to the stored
matrix, rather than one derived from a qform.

- rick