[Insight-users] Mean Curvature Calculation in Level Set
Sah Rayman
sahrayman at yahoo . com
Thu, 20 Nov 2003 21:25:38 -0800 (PST)
Lius,
Thanks for the help. Yeah, the design of the level set
function are elegant for me. When I want my own
curvature function, I can just write it in my own
class and everything is set.
But I still have this C++ question. In my
understanding, the situation could be simplified like
this:
int MyFunction(int a, int b, int c);
int main() {
MyFunction( 1, 2, 3);
return 0;
}
int MyFunction(int , int, int c) {
// don't use a and b
return c;
}
So, you mean:
1. MyFunction(int , int, int c) is leagal in C++?
2. Despite the declaration "int MyFunction(int a, int
b, int c)" and calling "MyFunction( 1, 2, 3)" we can
still implement MyFunction like this?
Thanks.
Sah
--- Luis Ibanez <luis . ibanez at kitware . com> wrote:
>
> Hi Sah,
>
> The ITK macro itkNotUsed() is converted to an
> empty string in most platforms.
>
> A method declaration/implementation like
>
> myMethod( int & itkNotUsed( x ) )
>
> is equivalent to
>
> myMethod( int & )
>
> this second expression is valid C++.
>
> ---
>
> ComputeMeanCurvature() is a virtual function.
>
> This means that it is declared in a base class
> and it is intended to be overloaded in derived
> classes. When a method in the base class
> (itkLevelSet) invokes "ComputeMeanCurvature()"
> the execution will be delegated to the
> "ComputeMeanCurvature()" as defined in the derived
> class.
>
> The elegance of the LevelSetFunction implementation
> that Josh did in ITK is that the generic
> computations
> are done at the top level in the base class, while
> the details of the specific type of partial
> differential
> equation to use are defined in the derived classes.
>
> In this way the common functionality is factorized
> in a central location at the level of the base class
> and the code doesn't have to be repeated for every
> new
> level set approach. If you look at the derived
> classes
> of SegmentationLevelSet:
>
http://www . itk . org/Insight/Doxygen/html/classitk_1_1SegmentationLevelSetFunction . html
> it becomes more evident how poweful this
> implementation is.
>
>
> Note for example that all this 8 different levelSet
> methods
> are sharing the basic math and only changing the way
> in
> which the actual components of the equation are
> computed.
>
>
> You may want to look at a good C++ textbook and
> check on the description of polymorphism, virtual
> functions, and abstract functions. That will give
> you
> a better background for following the implementation
> in ITK.
>
>
> Please let us know if you have further questions.
>
>
> Regards,
>
>
> Luis
>
>
> -------------------
> Sah Rayman wrote:
> > Hi Lius,
> >
> > Sorry I am still confused.
> >
> > First, I also don't use "neighborhood" or "offset"
> in
> > my implementation.
> >
> > If we take a look at itkLevelSetFunction.txx, Line
> > 158-162:
> > template <class TImageType>
> > typename
> LevelSetFunction<TImageType>::ScalarValueType
> >
> LevelSetFunction<TImageType>::ComputeMeanCurvature(
> > const NeighborhoodType
> &itkNotUsed(neighborhood),
> > const FloatOffsetType &itkNotUsed(offset),
> > GlobalDataStruct *gd)
> > { ...
> > }
> >
> > Does it euqavalent to the following? (just replace
> > itkNotUsed(AnyThing) to EMPTY)
> > template <class TImageType>
> > typename
> LevelSetFunction<TImageType>::ScalarValueType
> >
> LevelSetFunction<TImageType>::ComputeMeanCurvature(
> > const NeighborhoodType &,
> > const FloatOffsetType &, GlobalDataStruct *gd)
> > { ...
> > }
> >
> > Is the above a leagal C++ function implementation?
> >
> > Also, in the same file, function
> > ComputeCurvatureTerm() calls
> > ComputeMeanCurvature(neighborhood, offset, gd),
> then
> > where is it implemented?
> >
> > I never used those "advanced" C++ feature before.
> > Sorry if it's a naive qustions.
> >
> > Thanks.
> > Sah
> >
> >
> > --- Luis Ibanez <luis . ibanez at kitware . com> wrote:
> >
> >>Hi Sah,
> >>
> >>The itkNotUse() macro was used to make some
> >>compilers
> >>happy and avoid the warnings for "non used
> variable"
> >>in the cases where the arguments were not used in
> a
> >>method. This typically happens in virtual
> functions
> >>when in order to respect the API, a number of
> >>arguments
> >>are present, but not used inside the method.
> >>
> >>If your implementation of the method is actually
> >>using
> >>the argument of the function, you must then remove
> >>the
> >>itkNotUse() macro, otherwise the argument is not
> >>declared
> >>at all.
> >>
> >>The reason why there are not errors in
> >>itkLevelSetFunction
> >>is because the argument "neighbor" is not used in
> >>the
> >>ComputeMeanCurvature, so the signature could be as
> >>well:
> >>
> >> ComputeMeanCurvature( const NeighborhoodType &
> )
> >>
> >>
> >>
> >>Regards,
> >>
> >>
> >>
> >> Luis
> >>
> >>
> >>
> >
> >
>
--------------------------------------------------------
> >
> >>Sah Rayman wrote:
> >>
> >>>A related question: when I implement
> >>>ComputeMeanCurvature() in class
> >>
> >>MyLevelSetFunction.txx
> >>
> >>>If I write as
> >>>ComputeMeanCurvature(const NeighborhoodType
> >>>&itkNotUse(neighborhood), ...)
> >>>as it is in itkLevelSetFunction.txx, I will get a
> >>
> >>lot
> >>
> >>>syntax error (VC 6.0), and I have to write as
> >>>ComputeMeanCurvature(const NeighborhoodType
> >>>&neighborhood, ...)
> >>>
> >>>I checked the definition of itkNotUse(x), it is a
> >>>macro to nothing, (#define itkNotUse(x) )
> >>>
> >>>Then how come in itkLevelSetFunction.txx there is
> >>
> >>no
> >>
> >>>syntax error?
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>--- Sah Rayman <sahrayman at yahoo . com> wrote:
> >>>
> >>>
> >>>>I am now 90% sure that this is a bug of
> >>>>itkLevelSetFunction.txx as of ITK 1.4.
> >>>>
> >>>>I rewrote my ComputeMeanCurvature() in my
> derived
> >>>>LevelSetFunction class, and the segmentation
> >>>
> >>result
> >>
> >>>>makes more sense.
> >>>>
> >>>>My fix:
> >>>>move line "curvature_term -= gd->m_dx[i] *
> >>>>gd->m_dx[j]
> >>>>* gd->m_dxy[i][j];"
> >>>>to the inner of "if( j!=i) ".
> >>>>
> >>>>Author of the file, if you're interested in more
> >>>>details, please write to me.
> >>>>
> >>>>
> >>>>
> >>>>--- Sah Rayman <sahrayman at yahoo . com> wrote:
> >>>>
> >>>>
> >>>>>I am looking at function:
> >>>>>
> >>>>>template <class TImageType>
> >>>>>typename
> >>>>>LevelSetFunction<TImageType>::ScalarValueType
> >>>>>
> >>>>
>
>>>LevelSetFunction<TImageType>::ComputeMeanCurvature()
> >>>
> >>>>>in itkLevelSetFunction.txx, line 158 (ITK 1.4)
> >>>>>
> >>>>>When I compared that to Sethian's "Level Set
> >>>>
> >>>>Methods
> >>>>
> >>>>
> >>>>>and Fast Marching Methods", 2ndEd, pp. 70, Eq.
> >>>>
> >>>>6.36,
> >>>>
> >>>>
> >>>>>I
> >>>>>found that the C++ implementation contain some
> >>>>
> >>>>extra
> >>>>
> >>>>
> >>>>>terms in nominator:
> >>>>>
>
>>>>>-dx[0]*dx[0]*dxy[0][0]-dx[1]*dx[1]*dxy[1][1]-...
> >>>>>
> >>>>>Can someone tell me what are these additional
> >>>>
> >>>>terms
> >>>>
> >>>>
> >>>>>for? Is the result still mean curvature? Any
> >>>>>reference
> >>>>>for that?
> >>>>>
> >>>>>
> >>>>>__________________________________
> >>>>>Do you Yahoo!?
> >>>>>Protect your identity with Yahoo! Mail
> >>>>
> >>>>AddressGuard
> >>>>
> >>>>
> >>>>>http://antispam . yahoo . com/whatsnewfree
> >>>>>_______________________________________________
> >>>>>Insight-users mailing list
> >>>>>Insight-users at itk . org
>
>>>>>http://www . itk . org/mailman/listinfo/insight-users
> >>>>
> >>>>
> >>>>__________________________________
> >>>>Do you Yahoo!?
> >>>>Protect your identity with Yahoo! Mail
> >>>
> >>AddressGuard
> >>
> >>>>http://antispam . yahoo . com/whatsnewfree
> >>>>_______________________________________________
> >>>>Insight-users mailing list
> >>>>Insight-users at itk . org
>
>>>>http://www . itk . org/mailman/listinfo/insight-users
> >>>
> >>>
> >>>
> >>>__________________________________
> >>>Do you Yahoo!?
> >>>Protect your identity with Yahoo! Mail
> >>
> >>AddressGuard
> >>
> >>>http://antispam . yahoo . com/whatsnewfree
> >>>_______________________________________________
> >>>Insight-users mailing list
> >>>Insight-users at itk . org
> >>>http://www . itk . org/mailman/listinfo/insight-users
> >>>
> >>
> >>
> >>
> >>_______________________________________________
> >>Insight-users mailing list
> >>Insight-users at itk . org
> >>http://www . itk . org/mailman/listinfo/insight-users
> >
> >
> >
> > __________________________________
> > Do you Yahoo!?
> > Free Pop-Up Blocker - Get it now
> > http://companion . yahoo . com/
> > _______________________________________________
> > Insight-users mailing list
> > Insight-users at itk . org
> > http://www . itk . org/mailman/listinfo/insight-users
> >
>
>
>
__________________________________
Do you Yahoo!?
Free Pop-Up Blocker - Get it now
http://companion . yahoo . com/