[Insight-users] itkMatrix error: discards qualifiers??

[michiel mentink]

thank you, I'm putting versors on my list of things to look at.

cheers, Michael

On Tue, Mar 30, 2010 at 3:35 PM, Luis Ibanez <luis.ibanez at kitware.com>wrote:

> Hi Michiel,
>
> This is actually the reason why using Euler angles is a bad idea.
>
>           The lack of a standard for the order of
>           application of the individual rotations.
>
> plus their vulnerability to the gimbal lock problem:
>
>             http://en.wikipedia.org/wiki/Gimbal_lock
>
>
> http://en.wikipedia.org/wiki/Gimbal_lock#Loss_of_a_degree_of_freedom_with_Euler_angles
>
>
> ---
>
> I would strongly encourage you to use itk::Versors instead.
>
> Versors (Unit Quaternions) are an unambiguous representation of
> rotations.
>
>
>    Regards,
>
>
>          Luis
>
>
> ------------------------------------------------------------------------
> On Tue, Mar 30, 2010 at 9:11 AM, michiel mentink
> <michael.mentink at st-hughs.ox.ac.uk> wrote:
> > in
> > /itkEuler3DTransform.txx
> > the rotation is applied either in X Y Z order, or Z X Y order (standard),
> > where Y rotation is applied first.
> >
> > Indeed, if I try different orders of rotation, I get different outcomes.
> I
> > suppose this is due to round-off
> > errors.
> > Why is Z X Y chosen as the standard way of multiplication?
> >
> >
> > Z Y X
> > image->GetDirection():
> >  0.999695   0.0171452 0.0177517
> > -0.0174497  0.999701  0.0171452
> > -0.0174524 -0.0174497 0.999695
> >
> > X Y Z
> > image->GetDirection():
> > 0.999695    0.0174497 0.0174524
> > -0.0177543  0.99969   0.0174497
> > -0.0171425 -0.0177543 0.999695
> >
> > Z X Y
> > image->GetDirection():
> >  0.99969    0.0174497 0.0177543
> > -0.0177543  0.999695  0.0171425
> > -0.0174497 -0.0174524 0.999695
> >
> > cheers,
> >
> > Michael
> >
> >
> >
> >
> >
> > On Tue, Mar 30, 2010 at 12:18 PM, michiel mentink
> > <michael.mentink at st-hughs.ox.ac.uk> wrote:
> >>
> >> ah just after posting I found it (figures!)
> >>
> >> complete and correct code now:
> >>
> >>   const ImageType::DirectionType & direction = image->GetDirection()
> >>   std::cout << "direction: " << std::endl << direction << std::endl <<
> >> std::endl;
> >>
> >>   float angleX, angleY, angleZ;
> >>   angleX = angleY = angleZ = 1  *   vnl_math::pi / 180.0;             //
> >> in this case: rotation = 1 degree
> >>
> >>   const double cx = vcl_cos(angleX);
> >>   const double sx = vcl_sin(angleX);
> >>
> >>   typedef itk::Matrix<double,3,3> Matrix;
> >>   Matrix RotationX;
> >>   Matrix FinalRotation = image->GetDirection();
> >>
> >>   std::cout << "sin: " << sx << " Cos: " << cx << std::endl;
> >>
> >>   RotationX[0][0] = 1; RotationX[0][1] =   0; RotationX[0][2] = 0;
> >>   RotationX[1][0] = 0; RotationX[1][1] =  cx; RotationX[1][2] = sx;
> >>   RotationX[2][0] = 0; RotationX[2][1] = -sx; RotationX[2][2] = cx;
> >>
> >>   FinalRotation = direction*RotationX;
> >>
> >>   std::cout << "image->GetDirection(): " << std::endl <<
> >> image->GetDirection() << std::endl;
> >>   std::cout << "RotationX: " << std::endl << RotationX << std::endl;
> >>   std::cout << "FinalRotation: " << std::endl << FinalRotation <<
> >> std::endl;
> >>
> >>   image->SetDirection(FinalRotation);
> >>
> >>   std::cout << "image->GetDirection(): " << std::endl <<
> >> image->GetDirection() << std::endl;
> >>
> >>
> >> cheers, Michael
> >>
> >>
> >>
> >>
> >>
> >> On Tue, Mar 30, 2010 at 12:10 PM, michiel mentink
> >> <michael.mentink at st-hughs.ox.ac.uk> wrote:
> >>>
> >>> Hello Frederic,
> >>>
> >>> thanks for your suggestion.
> >>>
> >>> although my code was working, I tried your suggestion. Unfortunately,
> it
> >>> produces
> >>>
> >>> error: no match for ‘operator*’ in
> >>> ‘image.itk::SmartPointer<TObjectType>::operator-> [with TObjectType =
> >>> itk::Image<float, 3u>]()->itk::ImageBase<VImageDimension>::GetDirection
> >>> [with unsigned int VImageDimension = 3u] * RotationX’
> >>>
> >>>
> >>> Anyway, I forgot to mention to use:
> >>>
> >>>   float angleX, angleY, angleZ;
> >>>   angleX = angleY = angleZ = 1 * (3.14/180);
> >>>
> >>> (multiply by pi and divide by 180 degrees, because ITK internally works
> >>> with radians instead of degrees)
> >>>
> >>> Which leads me to the question: vnl has a pi constant, and I remember
> >>> vaguely having seen it somewhere as vnl::PI or something.
> >>> Does anyone know how to convince vnl to hand me pi constant?
> >>>
> >>> cheers, Michael
> >>>
> >>>
> >>>
> >>> On Tue, Mar 30, 2010 at 11:55 AM, Frederic Perez <
> fredericpcx at gmail.com>
> >>> wrote:
> >>>>
> >>>> Hello Michiel,
> >>>>
> >>>> perhaps you could use a const Matrix object after all, since it looks
> to
> >>>> me that FinalRotation is first built with image->GetDirection() but
> this
> >>>> value is not actually used, and that the signature of itk::Image's is
> >>>> SetDirection(const DirectionType direction).
> >>>>
> >>>> So here you are, my quickly written proposal (caution, I haven't
> >>>> compiled it):
> >>>>
> >>>>   float angleX, angleY, angleZ;
> >>>>   angleX = angleY = angleZ = 5;
> >>>>
> >>>>   const double cx = vcl_cos(angleX);
> >>>>   const double sx = vcl_sin(angleX);
> >>>>
> >>>>   typedef itk::Matrix<double,3,3> Matrix;
> >>>>   Matrix RotationX;
> >>>>   // Matrix FinalRotation = image->GetDirection(); -- Commented now
> >>>>
> >>>>   RotationX[0][0] = 1; RotationX[0][1] =   0;  RotationX[0][2] = 0;
> >>>>   RotationX[1][0] = 0; RotationX[1][1] =  cx; RotationX[1][2] = sx;
> >>>>   RotationX[2][0] = 0; RotationX[2][1] = -sx; RotationX[2][2] = cx;
> >>>>
> >>>>   const Matrix FinalRotation = direction*RotationX;
> >>>>
> >>>>   std::cout << "image->GetDirection(): " << std::endl <<
> >>>> image->GetDirection() << std::endl;
> >>>>   std::cout << "RotationX: " << std::endl << RotationX << std::endl;
> >>>>   std::cout << "FinalRotation: " << std::endl << FinalRotation <<
> >>>> std::endl;
> >>>>
> >>>>   image->SetDirection(FinalRotation);
> >>>>
> >>>>   std::cout << "image->GetDirection(): " << std::endl <<
> >>>> image->GetDirection() << std::endl;
> >>>>
> >>>> Cheers,
> >>>>
> >>>> Frederic
> >>>>
> >>>
> >>
> >
> >
>
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