[Insight-users] initialize VersorRigid3DTransform

[Dean Inglis]

Hi Bill,

I saw that class but didnt think I could use it since it takes two
images instead of a point set and an image. However, looking at the source
I see what needs to be done.  One could write variant initializer classes 
for pointset
to image registration or use PointSetToImageFilter and then pass its output
to the initializer.

thanks,
Dean

> Is this class useful?
> ./Registration/Common/include/itkCenteredVersorTransformInitializer
>
>
> On Sat, Oct 22, 2011 at 12:44 PM, Dean Inglis <dean.inglis at camris.ca> 
> wrote:
>
>> how can I initialize a VersorRigid3DTransform for a point set
>> to image registration problem using the following information:
>> 1) center of the moving points, c
>> 2) principal axes of the moving points, e1, e2, e3
>> 3) center of the image calculated using the ImageMomentsCalculator, cofg
>> 4) principal axes of the image calculated using the 
>> ImageMomentsCalculator,
>> p1, p2, p3
>>
>> where all variables above are double arrays of size 3?  Bascally, I would
>> like
>> to be able to initialize the transform:
>>   ParametersType parameters( transform->**GetNumberOfParameters() );
>>
>>  //  Versor type
>>   typedef    TransformType::VersorType      VersorType;
>>   VersorType versor;
>>
>>   parameters[0] = versor.GetX();   // Rotations
>>   parameters[1] = versor.GetY();
>>   parameters[2] = versor.GetZ();
>>   parameters[3] = 0.0;             // Translations
>>   parameters[4] = 0.0;
>>   parameters[5] = 0.0;
>>
>>
>>   transform->SetParameters( parameters );
>>
>> but I dont know how the rotations should be initialized.  I could 
>> calculate
>> a 3x3 rotation
>> matrix :
>> A = e * p
>> where e = {e1,e2,e3} and p = {p1,p2,p3} but how could that be used to
>> initialize the
>> transform?
>>
>> Dean
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>