[MINC-development] tfm_input_sampling

[Peter Neelin]

On 3/28/06, Pellegrini, Stefano (NIH/NINDS) [F]
<pellegrinis at ninds.nih.gov> wrote:

> might anybody tell me why when I use mincresample with
> -transform <identity.xfm> -tfm_input_sampling
> I get that in the output file the space:step and space:start attributes (and others, see below) are changed?
>
>  double xspace ;
>                 xspace:step = 0.9375 ;
>                 xspace:start = -115.585746765137 ;
>                 xspace:direction_cosines = -1., 0., 0. ;

The direction cosines should be in the positive direction.
mincresample will correct this on output. From the minc programmer's
reference (version 1.4, but unchanged from ancient versions):

Note that the dot product of the direction cosine with the
corresponding axis ((1,0,0), (0,1,0) or (0,0,1)) should be positive so
that the sign of the attribute MIstep contains the orientation
information.

Note that both step and start are negated. That is because they are
distances along the the axis vector - flipping the vector requires
negating them.

Peter
--
Peter Neelin
(peter.neelin at gmail.com)