[Insight-users] Curvature in Level Set

[Sah Rayman]

Joshua,

I am not sure if this is the answer to your question -
what is the solver. 

I derived a class from SegmentationLevelSetFunction.
It reads initial, speed, advection images from disk. 

To initialize, I used Matlab to generate a initial
curve mhd file, where inside my initial circle (radius
60) it is -1, and outside it is +1.


--- Joshua Cates <cates at sci.utah.edu> wrote:
> The std dev you are seeing does seem surprising.  It
> might be helpful
> to visualize the curvature values by writing them to
> a floating point
> image.  Which solver are you using to initialize and
> deform your circle?
> 
> Josh.
> 
> ______________________________
>  Josh Cates			
>  Scientific Computing and Imaging Institute
>  University of Utah
>  (801) 587-7697
>  http://www.sci.utah.edu/~cates
> 
> 
> On Fri, 5 Mar 2004, Sah Rayman wrote:
> 
> > I found some "wierd behavior" of the curvature
> > calculated in SegmentationLevelSetFunction. 
> > 
> > While I expect the curvature to be 0.0125
> everywhere, 
> > the actual curvature has a mean of 0.0137 (which
> is
> > good), but a s.t.d of 0.4. In another words, when
> the
> > tangent circle is actually of radius 80, the
> > calculation tells me the radius is 2 or 1 at some
> edge
> > points, and even concave in some other points.
> > 
> > Is it true that there are errors in curvature
> > calculation in the range of my discription? Or,
> there
> > must be something wrong in my application?
> > 
> > ======================================
> > Here is what I do in the test.
> > 
> > Full image is 256x256, ground truth is a circle
> whose
> > radius is 80 pixels, initial is a 60-pixel-radius
> > circle with a same center.
> > 
> > I disabled advection, curvature term, and there
> are
> > only speed term. Speed is +1 inside my ground
> truth,
> > and -1 otherwise. In fact, curvature weight is
> 1e-6 to
> > enable the curvature calculation.
> > 
> > After 180 iterations, I observe the output of
> > ComputeMeanCurvature() for one iteration, and take
> > statistics.
> > 
> > The output segmentation matches well with my
> ground
> > truth.
> > ======================================
> > 
> > 
> > 
> > 
> > 
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> 


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