[Insight-users] Fwd: Re: Parameter scales for registration (second try)

[brian avants]

Hi joel

I think its clear ... do you want to implement this approach in v4 ?   the
"regular step" type behavior is what we achieve by other methods in v4 -
i.e. the steps detailed to you previously.   we can help with a v4
implementation of the v3 version, if you like.

if you prefer to fix v3 then, as brad said, there are several tests that
will need adjustment.  am sure someone would help with that too.

b

---------- Forwarded message ----------
From: "Joël Schaerer" <joel.schaerer at gmail.com>
Da
>
>  Hi Nick,
>
> What I called the "first scaling" is the application of scales that is
> done before gradient normalization, in the AdvanceOneStep method:
>
> itkRegularStepGradientDescentBaseOptimizer.cxx
> 187   for ( unsigned int i = 0; i < spaceDimension; i++ )
> 188     {
> 189     transformedGradient[i]  = m_Gradient[i] / scales[i];
> 190     previousTransformedGradient[i] =
> 191       m_PreviousGradient[i] / scales[i];
> 192     }
>
> The "second scaling" would be my proposed change, replacing
>
> itkRegularStepGradientDescentOptimizer.cxx
>  42   for ( unsigned int j = 0; j < spaceDimension; j++ )
>  43     {
>  44     newPosition[j] = currentPosition[j] + transformedGradient[j] *
> factor;
>  45     }
>  46
>
> with
>
> itkRegularStepGradientDescentOptimizer.cxx
>  42   for ( unsigned int j = 0; j < spaceDimension; j++ )
>  43     {
>  44     newPosition[j] = currentPosition[j] + transformedGradient[j] *
> factor  / scales[j];
>  45     }
>  46
>
> basically a second application of the parameter scales.
>
> I hope this is clearer?
>
> joel
>
> On 07/05/2013 23:22, Nick Tustison wrote:
>
> Hi Joel,
>
>  Also, could you clarify your question a bit?  The snippet of interest in
> the old itkRegularStepGradientOptimizer is
>
>    for(unsigned int j=0; j<spaceDimension; j++)
>     {
>     newPosition[j] = currentPosition[j] + transformedGradient[j] * factor;
>     }
>
>  When you write of "first scaling" are you referring to multiplication by
> "factor"?
>
>  Nick
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.itk.org/pipermail/insight-users/attachments/20130513/5a88a10d/attachment.htm>