[vtkusers] Curious about differences in vtkMassProperties for VTK 5.04 and VTK 5.4.2

[Azim]

Hi All,

I have a small python VTK function (pasted in at the bottom of this email) that calculates the volume and surface area of an object embedded in a stack of TIFF images.  To read the TIFFs into VTK I have used vtkTIFFReader and processed the result using vtkImageThreshold and vtkImageGaussianSmooth libraries.  I then use vtkMassProperties to extract the volume and surface area of the object identified after smoothing and thresholding.  

With VTK-5.04, this function returns the correct value for a test stack (3902 pixels). However, the same function returns a different value (422 pixels) when I run it using VTK-5.4.2. Can someone explain this.

Thank you in advance for all your responses/help

Azim


Python Code Below

### Start File ###
import vtk
def testvtk():
    # read 36 TIFF images. Each TIFF is 27x27 pixels
    v16=vtk.vtkTIFFReader()
    v16.SetFilePrefix("d:/test/slice")
    v16.SetDataExtent(0,27,0,27,1,36)
    v16.SetFilePattern("%s%04d.tif")
    v16.SetDataSpacing (1,1,1)
    v16.Update()

    # Threshold level for seperating background/foreground pixels
    maxthres=81

    # Threshold the image stack
    thres=vtk.vtkImageThreshold()
    thres.SetInputConnection(v16.GetOutputPort())
    thres.ThresholdByLower(0)
    thres.ThresholdByUpper(maxthres)

    # create ISO surface from thresholded images
    iso=vtk.vtkImageMarchingCubes()
    iso.SetInputConnection(thres.GetOutputPort())

    # Have VTK calculate the Mass (volume) and surface area
    Mass = vtk.vtkMassProperties()
    Mass.SetInputConnection(iso.GetOutputPort())
    Mass.Update() 

    # just print the results
    print "Volume = ", Mass.GetVolume() 
    print "Surface = ", Mass.GetSurfaceArea()

testvtk
### End File ###
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