[vtkusers] Different alignment between application and paraview

[Scott Johnson]

Hello,

My platform is:  Windows 7 64-bit, Visual Studio 2008, and Activiz 5.8.

I developing an application which is attempting to segment out a linear feature in a CT scan and determine its orientation.  In my application I am able to find the feature, but the image data does not seem to align with the segmentation.  If I export the segmentation and image data to paraview things align as expected.

The pipeline to perform the segmentation in my application is:  vtkImageData->vtkImageContinuousDilate3D->vtkMarchingCubes->vtkPolyDataNormals->vtkPolyDataConnectivityFilter.

The snapshot from my application is attached (Application.jpg).  The light colored pixels represent the feature I am attempting to find.  The red surface is the result of vtkPolyDataConnectivityFilter.  The green box is the bounds around the dilated feature and the yellow line is my computed orientation.  In this image you can see that some of the light colored features protrude from the dilated area.  The dilation uses a 5x5x5 kernel.  This is not what I would expect.  Because of this misalignment my computed orientation is not correct.

The snapshot from paraview is attached (Paraview.jpg).  I exported the image data from my application to a vti file and imported it into paraview.  The pink voxels are the result of paraview thresholding the light colored voxels representing my feature from the image data.  The grey surface was exported to a vtp file from the vtkPolyDataConnectivityFilter in my application and imported into paraview.  In this display you can see that the pink voxels are within the segmented surface.  This is what I would expect.

Does anyone have any hints as to why the alignment in my application may be different than that in Paraview?  Any pointers would be appreciated.

Thanks

                                -- Scott

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