[Insight-users] Curvature in Level Set

[Joshua Cates]

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=09=09=09
 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.=20
>=20
> While I expect the curvature to be 0.0125 everywhere,=20
> 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.
>=20
> 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?
>=20
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> Here is what I do in the test.
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> 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.
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> 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.
>=20
> After 180 iterations, I observe the output of
> ComputeMeanCurvature() for one iteration, and take
> statistics.
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> The output segmentation matches well with my ground
> truth.
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>=20
>=20
>=20
>=20
>=20
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>=20