[IGSTK-Developers] SpatialObject calibration transform

[David Gobbi]

Hi Patrick,

Thanks for the summary.  The reason that I would prefer to add the 
orientation as part of the tool calibration transform is that I think we 
should keep the number of coordinate transformations in IGSTK to a minimum.

Each coordinate transformation is a possible source of error.  Even 
worse, if two different transformations can be used to achieve the same 
result (e.g. a tool calibration transform and a spatial object 
calibration transform), then both transforms can have errors that cancel 
each other out.  These sorts of errors can be very hard to debug.

I think the best solution is if the ToolTipCalibration class has a 
method that allows you to specify the orientation of the tool that is 
being calibrated.

 - David

Patrick Cheng wrote:

> Hi everybody,
>
> What I was trying to say in the Tcon is:
>
> the cylinder object (longest axis) is align with Y axis in image space 
> (inherited from ITK by default). while the probe is aligned with the 
> tracker's X axis.
>
> So when we get the PatientTransform, which essentially align the image 
> space and tracker space together, but still the cylinder spatialobject 
> and the probe is not aligned correctly. We need first rotate our 
> spatial object to align with the probe, and then use the pivot 
> calibration transform to get the tip translation.
>
> This adjustment of the spatial object's coordinate system, can be done 
> by adding the rotational information to tool calibration transform. or 
> we can add it to a upper level transform when we construct a spatial 
> object group to model the probe.
>
> Patrick