[Rtk-users] Problem with itk 4.8.1 when using rtk::FDKConeBeamReconstructionFilter

[Simon Rit]

Hi Thibault,
No, there is not really a log system that would allow you debugging at run
time. You can compile a debug version that would enable a lot of messages
related to the pipeline. For this, I think you need to use NDEBUG at
compilation (it's an ITK mechanism that I never use).
No, it's not normal that you see an error message. There are two things:
- the FFT of itk (compiled by default, based on vnl) is really bad IMO: it
only handles power of 2/3/5 dimensions and it's slow. I always advise
people to use FFTW by turning on ITK_USE_FFTW options during ITK's
compilation.
- I don't fully understand why vnl doesn't work either. I understand the
first two dimensions, for vnl (which I strongly suggest to not use), I pad
to the next power of 2 so
780 * 2 (for zero padding) -> 2048
780 -> 1024
but then, if you use 64 projections, why 11? Are you sure the second input
image to FDKConeBeamReconstructionImageFilter has the dimension you want? I
would try to connect input 2 to an itk::ImageFileWriter and check what are
the dimensions of this image. If you're absolutely sure, then I'll try to
reproduce and fix the issue.
Simon

On Wed, Oct 14, 2015 at 11:38 AM, Notargiacomo Thibault <
gnthibault at gmail.com> wrote:

> Dear all,
>
> I recently had troubles while trying to rewrite my code, linked with
> libRTK / libRTKcuda, from using rtk cuda version of SART, that worked quite
> well, to using fdk reconstruction method.
>
> My first question: is there a general way to enable maximum debug log
> level at runtime in rtk ?
>
> My second question, is more specific: is it normal that I see such error
> message coming from itk when using FDKConeBeamReconstructionFilter :
>
> ExceptionObject caught with fdk->Update() in file [...]
>
> itk::ExceptionObject (0x7f377c020cb0)
> Location: "unknown"
> File: [...]/itk-4.8.1/Modules/Core/Common/src/itkMultiThreader.cxx
> Line: 416
> Description: itk::ERROR: MultiThreader(0x1866340): Exception occurred
> during SingleMethodExecute
>
> /usr/local/include/ITK-4.8/itkVnlRealToHalfHermitianForwardFFTImageFilter.hxx:60:
> itk::ERROR: VnlRealToHalfHermitianForwardFFTImageFilter(0x7f377c0207d0):
> Cannot compute FFT of image with size [2048, 1024, 11].
> VnlRealToHalfHermitianForwardFFTImageFilter operates only on images whose
> size in each dimension has a prime factorization consisting of only 2s, 3s,
> or 5s.
>
> I suppose that this error arise while performing ramp filtering, but I see
> no relation between FFT configuration stated in the error log ( [2048,
> 1024, 11] ) and the size of my input image, which is 780 * 720, over 64
> projections.
>
> I also tried with 200 projection and I had the same problem, but with
> [2048, 1024, 34]
>
> Note that I set my FDKConeBeamReconstructionFilter ProjectionSubsetSize to
> the total number of projection in my dataset every time.
>
> The revision I am currently using:
> commit 4993ddfca5b3d59a2fcf71f94890036ede610a08
> Merge: 578cf89 09d820c
>
>
> Thank you in advance for your help.
>
> Regards
>
> Thibault Notargiacomo
>
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