[IGSTK-Developers] Landmark 3D Registration

[Zein Salah]

Thanks Ziv!

I actually realized that the register has nothing to do with the image itself.

I here have another question: I am using four point pairs for registering
an image to real world position. First, I got an output transform that did not
seem to generate the correct rendering. I thought that I might have imagined
the transformation conversely. So, I exchanged the point pairs,
something like this:

for (int i=0; i<fiducialsNumber; i++) {
			imagePoint[0] =  fiducial[i].fid_indata_position[0]*volSpacing[0];
			imagePoint[1] =  fiducial[i].fid_indata_position[1]*volSpacing[1];
			imagePoint[2] =  fiducial[i].fid_indata_position[2]*volSpacing[2];
			landmarkRegister->RequestAddImageLandmarkPoint(trackerPoint);

                        trackerPoint[0] =  fiducial[i].fid_world_position[0];
                        trackerPoint[1] =  fiducial[i].fid_world_position[1];
                        trackerPoint[2] =  fiducial[i].fid_world_position[2];

landmarkRegister->RequestAddTrackerLandmarkPoint(imagePoint);
}

Note that image points are fed in place of tracker positions and vise versa.
I expected to also get the inverse of the original transfromation
matrix. But this
produced an identity matrix.

Am I thinking correctly? or I am missing something ?

Best,
Zein



On Wed, Dec 21, 2011 at 7:17 PM, Ziv Yaniv <zyaniv at childrensnational.org> wrote:
> Hello Zein,
>
> The "igstkLandmark3DRegistration " does not know about image spacing. It
> receives points in two coordinate systems
> "TrackerLandmarks" and "ImageLandmarks". It is implicitly assumed that both
> have the same (metric) units. It is up to you to convert image coordinates
> into physical/metric coordinates and and then pass those to the registration
> class.
>
>                regards
>                      Ziv
>
>
> On 12/21/2011 12:08 PM, Zein Salah wrote:
>>
>> Hi,
>>
>> does the class "igstkLandmark3DRegistration" actually take image
>> spacing into account when it compute the rigid transform?
>>
>> Thanks,
>> Zein
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>
>
>
> --
> Ziv Yaniv, PhD.,
> Principal Investigator,
> The Sheikh Zayed Institute for Pediatric Surgical Innovation
> Children's National Medical Center
> 6th Floor Main Hospital, Room M7740
> 111 Michigan Ave., N.W
> Washington, D.C 20010
>
> Phone: 202-476-1288
> email: zyaniv at childrensnational.org
> web: http://isiswiki.georgetown.edu/zivy/
>