[Insight-users] Possible bug: itkImageToVTKImageFilter not updating when expected

[Parag Chandra]

Hey Luis,

Yes, the slider also manually calls Render(). Really the only difference I
can think of between the two applications is the manner in which the image
is provided as input.

Best regards,
-Parag

----- Original Message -----
From: "Luis Ibanez" <luis.ibanez@kitware.com>
To: "Parag Chandra" <pchandra@radonc.unc.edu>
Cc: "ITK Mailing List" <insight-users@public.kitware.com>
Sent: Friday, March 21, 2003 6:22 PM
Subject: Re: [Insight-users] Possible bug: itkImageToVTKImageFilter not
updating when expected


>
> Hi Parag,
>
> Does the callback for the slider also calls Render()
> on the interactors render window ?
>
> In addition to switching the input image, you may want
> to call Render() again, since the pipeline is driven by
> demand, changing inputs will not force the update of
> filters downstream.
>
>
> You have to pull data from the end of the pipeline.
>
>
>
> Regards,
>
>
>     Luis
>
>
> ------------------------------------
>
> Parag Chandra wrote:
> > I'm seeing a problem where my ITK->VTK pipeline isn't getting updated
> > correctly, but a seemingly unnecessary workaround fixes the problem, so
> > I thought this might be a bug.
> >
> > In short, I have subclassed vtkFlRenderWindowInteractor to
> > create HeightFieldInteractor, which simply takes an input ITK 2D image
> > and displays it as a height field, using itkImageToVTKImageFilter. I've
> > then created an application that embeds this HeightFieldInteractor
> > widget into its main window. The application just lets you load an ITK
> > image from disk and then displays it as a height field. So the pipeline
> > is something like:
> >
> > itkImageFileReader -> itkImageToVTKImageFilter ->
> > vtkImageDataGeometryFilter -> vtkWarpScalarFilter -> vtkPolyDataMapper
> > -> vtkActor
> >
> > This application works perfectly: as soon as I load a new image from
> > disk, I call Render() on the interactor's RenderWindow, and the window
> > is updated to reflect the contents of the new image.
> >
> > A second application embeds both the same HeightFieldInteractor and an
> > additional instance of vtkFlRenderWindowInteractor into its main window.
> > This application loads a series of a dozen or so 2-D ITK images at
> > startup and keeps them around in a std::vector. I then use a slider to
> > select between these images, and the callback for the slider simply sets
> > the input of itkImageToVTKImageFilter to the appropriate image stored in
> > the vector. So the pipeline is something like this:
> >
> > vectorOfImages[sliderValue] -> itkImageToVTKImageFilter -> etc.
> >
> > In this instance, the render window never gets updated no matter how
> > many times the slider is moved around; it always shows the first image
> > that was set. I even tried manually calling Modified() and Update() on
> > the itkImageToVTKImageFilter, as well as manually Update()'ing other
> > filters farther up/down the pipeline, but to no avail. However, if I
> > insert a simple CopyFilter that I created into the pipeline above:
> >
> > vectorOfImages[sliderValue] -> myCopyImageFilter ->
> > itkImageToVTKImageFilter -> etc.
> >
> > then the updates happen correctly. This CopyImageFilter simply copies
> > the input image over to the output unchanged.
> >
> > Does someone with a better knowledge of the internal workings of ITK and
> > VTK have an idea what might be going on here? I should again note that
> > I'm still using ITK 1.0 and VTK 4.0 on Windows, so sorry if this has
> > already been fixed. I'm just holding off on upgrading to the latest
> > versions until I reach certain milestones in my project. Thanks.
> >
> > Best regards,
> > -Parag Chandra
>
>
>