[IGSTK-Users] Tip and Origin Translation Coordinates

[Fauze Polpeta]

Hi Jake and Patrick;

I'm using the standard ROM file and rotating the probe about it's mechanical
axis. I'm not at the lab right now, but the information that the tool
coordinate
system is defined at the center of 'Marker A' makes a lot of sense. Tomorrow
I will confirm that I'm moving in a circle with 3D support.

Patrick, in this case, a pivot calibration wouldn't help right? As mentioned
this is the case where a "rotational calibration (non-orthogonal)" should
take place.

Thank you both for supporting me.

Best Regards

Fauze


On Thu, Jan 21, 2010 at 8:01 PM, Patrick Cheng <cheng at isis.georgetown.edu>wrote:

> Hi Jake,
>
> There is a pivot calibration class and example in IGSTK 4.2.
>
> Please refer to "Chapter 16 Calibration" of the IGSTK book, 2nd edition,
> page 225.
>
> Patrick
>
>
> On 1/21/2010 3:52 PM, Jake McIvor wrote:
>
>> Hello Fauze,
>>
>> Are you using the standard .rom file for your pointer tool?  Based on
>> the Vicra Tool Guide I have seen (2006 version), the tool coordinate
>> system is defined at the center of 'Marker A', or the marker closest
>> to the tip of the tool.  It is offset from the mechanical axis of the
>> pointer shaft.
>>
>> If you are rotating about the mechanical axis of the pointer shaft,
>> then the origin of the tool should be moving in a circle.  Could this
>> be the source of the movement?
>>
>>
>> Patrick:
>> I remember coming across a mention of an IGSTK rotational calibration
>> class some time ago.  Is this still in development?
>>
>>
>> Cheers,
>> Jake
>>
>> --
>> Jake McIvor
>> MASc Candidate, Biomedical Engineering
>> University of British Columbia
>>
>> On Thu, Jan 21, 2010 at 10:20 AM, Patrick Cheng
>> <cheng at isis.georgetown.edu>  wrote:
>>
>>> Hi Fauze,
>>>
>>> ...When we "rotate" the tool around it's own axis without any tip and
>>> origin
>>> translations...
>>>
>>> When you say "rotate", do you mean "Pivot"? If that the case, then you
>>> probably didn't set the "calibration transform" right.
>>>
>>> If you just "rotate" your needle, the object being displayed should not
>>> move
>>> at all, even without proper "tip calibration (translational)", because we
>>> only have 5 degree-of-freedom sensor. If it does move, it means the
>>> sensor's
>>> principle axis is not aligned with your needle's principle axis, then you
>>> need to do a "principle axis calibration (orthogonal axis swap)" or
>>> "rotational calibration (non-orthogonal)".
>>>
>>> Patrick
>>>
>>> On 1/21/2010 1:07 PM, Fauze Polpeta wrote:
>>>
>>>>
>>>> Dear Patrick;
>>>>
>>>> After applying the registration transform to a tool (consider the NDI
>>>> Vicra Standard Probe - 8700340) and start the navigation, we've noticed
>>>> a strange behavior in our 2D tool representation, which, in turn, is a
>>>> line drawn in three OpengGL contexts (MPR). When we rotate the tool
>>>> around it's own axis without any tip and origin translations, we faced
>>>> that the origin is being shifted as it was being translated, but it's
>>>> not.
>>>>
>>>> In order to draw the line that represents the tool we use the
>>>> tipTransform (obtained on each track event) and the (inverse)
>>>> calibration transform (see code below). Thus, with tip and origin
>>>> translations in hands the line can be drawn. At a first glance I thought
>>>> this was caused by a high registration error, but it's not, even with
>>>>  such error below 3.0 this scenario remains. Is this caused by the way
>>>> we are getting the origin's coordinates back? Should we rely on the
>>>> rotation instead of origin translation?
>>>>
>>>> Thanks in advance for any suggestion.
>>>>
>>>> Regards
>>>>
>>>> Fauze
>>>>
>>>>
>>>> ----
>>>>
>>>> INPUT: tipTransform and calibrationTransform
>>>>
>>>> igstk::Transform inverseCalibrationTransform
>>>> = calibrationTransform.GetInverse();
>>>> igstk::Transform originTransform = igstk::Transform::TransformCompose(
>>>> tipTransform, inverseCalibrationTransform );
>>>> igstk::Transform::VectorType tipTranslation =
>>>> tipTransform.GetTranslation();
>>>> igstk::Transform::VectorType originTranslation =
>>>> originTransform.GetTranslation();
>>>>
>>>> OUTPUT: tipTranslation and originTranslation
>>>>
>>>>
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