[Insight-users] Optical flow visualization

[Ivan Macia]

Hi all,

Regarding the visualization of vector fields I would also like to visualize
the GAC vector field using vtk glyphs and incorporate this into my
application. From what I understand I would need to export my vectorial
image to vtk but I have seen that the itkVTKImageExport currently doesn't
support exporting vectorial images.
So I see two ways of achieving this right now without using an intermediate
file :

a) Extract every component, exporting every resulting scalar image from itk
to vtk and then join the components again in vtk.
b) Modify the classes so a vectorial image can be exported. I have had a
first look at the classes and seems that the limitation comes from the
itk::VTKImageExport class but i'm not very sure if vtkImageImport class
(from vtk libs) should be adapted too. Does this imply a big difficulty? If
not maybe I could give it a try, otherwise I would choose a) if it is
feasible.

Thanks in advance

Ivan


> -----Mensaje original-----
> De: insight-users-admin@itk.org [mailto:insight-users-admin@itk.org]En
> nombre de Luis Ibanez
> Enviado el: miercoles, 19 de mayo de 2004 22:08
> Para: Jayant Chauhan
> CC: insight-users@itk.org
> Asunto: Re: [Insight-users] Optical flow visualization
>
>
>
> Hi Jayant,
>
> There are two things that you could interpret as being
> the "optical flow" in the GeodesicActive contours.
>
> A) The advection image
>
> B) The displacements of the zero set
>     from one iteration to another.
>
> If what you have in mind is (A), then you can
> visualiza it by calling
>
>
>      GACFilter->GetAdvectionImage()
>
> this will return a vector image that you can save
> in order to visualize with ParaView, or that you
> can pass to VTK and apply glyhphs on it.
>
>
> If what you have in mind is (B), then it is more
> tricky because the only thing you will have is the
> position of the zero set at one iteration and the
> position of the level set at the previous iteration.
>
> Since the zero set doesn't move more that one pixel
> at each iteration, you could visit all the pixels
> from the zero set of one iteration and read the
> values of the Level set from the past iteration
> (that means that you have to save the level set
> of the previous iteration in an auxiliary image).
>
> Those values will tell you how far the current
> contour is now from its previous position.
> and therefore it is a measure of the optical
> flow of the level set at that iteration.
>
>
> Please let us know if that's what you had
> in mind.
>
>
>     Thanks
>
>
>       Luis
>
>
> --------------------
> Jayant Chauhan wrote:
>
> > Hey Luis,
> >
> > How can I visualize the optical flow (I am using
> > GeodesicActiveContourLevelSetImagefilter)? Is the optical
> flow the same
> > as the Speed image ?! Do I hve to use the function GetSpeedImage or
> > something lke taht ?! A pointer would help.
> >
> > with regards
> > Jayant
> >
>
>
>
>