[vtk-developers] updating the update extent?

[Stephen Langer]

Hi --

I've created a subclass of vtkRectilinearGridAlgorithm that converts 3D vtkImageData into a 3D rectilinear grid.  When I use it in a pipeline it appears to work correctly, until I replace the original image data with a smaller image.  When I do that, I see a message like this:

vtkStreamingDemandDrivenPipeline (0x7fd54243e120): The update extent specified in the information for output port 0 on algorithm oofImageToGrid(0x7fd54243db00) is 0 100 0 100 0 100, which is outside the whole extent 0 10 0 10 0 10.

What is the correct way to tell the algorithm that the image size has changed?  I thought that the downstream parts of the pipeline would be automatically updated when the upstream data changed.  I have redefined RequestUpdateExtent, but it's not called until after the error message appears.

I've attached my filter (oofImageToGrid.C, oofImageToGrid.h) and a test program that uses it (replaceimage3.C).  Running "replaceimage3 -1 bigimage -2 littleimage" will demonstrate the problem, where bigimage and littleimage are directories containing image slices, and bigimage is larger, voxel-wise, than littleimage.

Thanks for any advice!

      -- Steve

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