[IGSTK-Developers] calibration (followup to David and James'sdiscussion)

[Hui Zhang]

Hi, David,

Thanks for your comments.

Yes, I am not quite sure about the quaternion we calculated is the rotation 
from the default orientation to the input orientation, or its inverse one. 
The quaternion computation is always so ....

Perhaps Patrick can help test this class in his example application to see 
whether the computed quaternion is a correct one or an inverse one. Another 
method I think is we can try to provide a RequestInverseRotation function to 
manually reverse the rotation matrix if the user find the result is inverse?

Regards,

>
> We do in fact want the principal axis and plane normal to define a 
> rotation via a quaternion.  To be precise, we want to create a quaternion 
> that will rotate the raw tool coordinates such that the principal axis 
> (i.e. the tool shaft) becomes the local Z axis in spatial object 
> coordinates and the plane normal (i.e. the minor axis or flattest 
> direction) becomes the Y axis.
>
> I have looked at your code, and it looks good, it even recomputes the 
> normal to be perpendicular to the axis as it should.  The big danger, of 
> course, is accidentally building the rotation matrix the wrong way around 
> and ending up with the inverse rotation.
>
> - David
>
>> ----- Original Message ----- From: "David Gobbi" <dgobbi at atamai.com>
>> To: "Hui Zhang" <zhang at isis.imac.georgetown.edu>
>> Cc: "'IGSTK-developers'" <igstk-developers at public.kitware.com>
>> Sent: Thursday, December 01, 2005 5:36 PM
>> Subject: Re: [IGSTK-Developers] calibration (followup to David and 
>> James'sdiscussion)
>>
>>
>>> Yes, I think that the igstkReferenceCalibration should be added to the 
>>> wiki.  I'm interested to see what the interface to the class will look 
>>> like.
>>>
>>> Hui Zhang wrote:
>>>
>>>> Hi,
>>>>
>>>> This sounds good, I will put these two functions in the Wiki's class 
>>>> requirement soon. Do we also need add that igstkReferenceCalibration 
>>>> class in the Wiki? That is a general class to calculate the reference 
>>>> transform between the object position/orientation to reference 
>>>> position/orientation, which can also be used for Ziv's proposed routine 
>>>> to get the rotation?
>>>> Regards,
>>>> James
>>>> ----- Original Message ----- From: "David Gobbi" <dgobbi at atamai.com>
>>>>
>>>>>
>>>>> We will need intuitive methods for setting the orientation, because 
>>>>> not many people are familiar enough with quaternions.  So there could 
>>>>> be two methods:
>>>>>
>>>>> SetToolPrincipalAxis(vx, vy, vz) -- set a vector that points along the 
>>>>> tool axis towards the tool top
>>>>> SetToolFaceNormal(nx, ny, nz) -- set a vector to define a  that "face" 
>>>>> of the tool, this vector must be perpendicular to the tool axis
>>>>>
>>>>> The "tool face" is for when you want to use a pointer as a virtual 
>>>>> ultrasound probe, it will define the orientation of the plane that you 
>>>>> want to use as the virtual ultrasound plane.  This is only useful for 
>>>>> 6DOF tools, not for 5DOF tools.
>>>>>
>>>>> These two vectors can be put together to create the quaternion that is 
>>>>> used as the orientation.  The NDI tool architect software does 
>>>>> something very similar to this.
>>>>>
>>>>> - David
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>>
>
>
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