[vtkusers] vtkImageActor always updating

[Toon Huysmans]

Hi folks,

I want to visualize an image and overlay its segmentation. The visualisation
is done using three
orthogonal vtkImageActors.  I use the folowing pipeline:

ITKOriginal ->
  ImageToVTKImageFilter ->
      vtkImageMapToColors(GrayscaleLUT)        \

|-> vtkImageBlend -> 3 x vtkImageActor
      vtkImageMapToColors(RandomColorLUT) /
  ImageToVTKImageFilter ->
ITKSegmented ->

It seems to work fine, the image is displayed in grayscale and the
segmentation is overlayed in red
with a certain opacity.

But there are two problems:

    -When I change the camera using the mouse, or anything else that invokes
a render-call, the pipeline
        is somehow completely updated.  My progressbar indicates that each
filter is updated, only it
        happens much fater than for the first time. None the less, it is way
too slow and I cant see why
        it should be like this.

    -One other thing is, that I am not sure how to change the slice for an
ImageActor, Should I update
        the DisplayExtent or use SetZSlice ?  For now I use the first
approach but it has unstable
        behaviour, such as a disappearing ImageActor or even a program crash
(access violation).

I hope someone has similar experiences and can help me.

Thanks,

Toon