Hi Luis,<br> thanks for the quick reply. Nope, I do not believe I have enabled this flag. I am confused, I did take a look at the code snippet you suggested and figured that time step is <= 1/2^(N+1) not 1/2^N (Judging from line 75 and/through 81). In reality I believe this has to be 1/2^N as you suggested, at least if the implementation is same as Perona and Malik.. <br>
<br>just in case my metadata looks as follows :<br><br>NDims = 3<br>DimSize = 256 256 256<br>ElementType = MET_SHORT<br>ElementDataFile = raw256.raw<br><br><br>Again, thanks for the help!<br><br>Cheers,<br><br>C.S.N<br><br>
<br><br><div class="gmail_quote">On Mon, Feb 15, 2010 at 2:00 PM, Luis Ibanez <span dir="ltr"><<a href="mailto:luis.ibanez@kitware.com">luis.ibanez@kitware.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi Natarajan,<br>
<br>
<br>
<br>
"Glimpsing at the Source, leaves no doubt"<br>
<br>
<br>
This is what the file:<br>
<br>
Insight/Code/BasicFilters/itkAnisotropicDiffusionImageFilter.txx<br>
<br>
has in lines 75-82:<br>
<br>
<br>
if ( m_TimeStep > (minSpacing / vcl_pow(2.0,<br>
static_cast<double>(ImageDimension) + 1)) )<br>
{<br>
// f->SetTimeStep(1.0 / vcl_pow(2.0,<br>
static_cast<double>(ImageDimension)));<br>
itkWarningMacro( << "Anisotropic diffusion unstable time step: "<br>
<< m_TimeStep << std::endl<br>
<div class="im"> << "Stable time step for this image must be smaller than "<br>
</div> << minSpacing / vcl_pow(2.0,<br>
static_cast<double>(ImageDimension+1)));<br>
}<br>
<br>
<br>
In summary:<br>
<br>
Timestep < pixelSpacing / ( 2^N )<br>
<br>
where N is the image dimension (e.g. 3 for 3D images, and 2 for 2D images).<br>
<br>
<br>
<br>
<br>
Did you enable the flag:<br>
<br>
UseImageSpacing ?<br>
<br>
If so, what is the pixel spacing of your image ?<br>
<br>
<br>
Regards,<br>
<br>
<br>
<br>
Luis<br>
<br>
<br>
-------------------------------------------<br>
<div><div></div><div class="h5">On Mon, Feb 15, 2010 at 12:27 PM, Natarajan CS <<a href="mailto:csnataraj@gmail.com">csnataraj@gmail.com</a>> wrote:<br>
> Hello all,<br>
> Not sure if this is a bug or a implementation detail I am overlooking,<br>
> I am tending towards the latter, so any info would be helpful !<br>
> I get the following warning from the<br>
> GradientAnisotropicDiffusionImageFilter (The filter is being applied to a<br>
> 256^3 dataset of type short)<br>
><br>
> WARNING: In<br>
> /hpc/soft/natac0/itk/include/InsightToolkit/BasicFilters/itkAnisotropicDiffusionImageFilter.txx,<br>
> line 78<br>
> GradientAnisotropicDiffusionImageFilter (0xbc4120): Anisotropic diffusion<br>
> unstable time step: 0.07<br>
> Stable time step for this image must be smaller than 0.0625<br>
><br>
> i was under the impression that the ITK implimentation was a explicit method<br>
> with the time step requirement for 3D images is <= 1/8 and <= 1/4 for 2D. Am<br>
> i completely off-track here?<br>
><br>
> Appreciate any help!<br>
><br>
> Thanks,<br>
><br>
> C.S.N<br>
><br>
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