[Insight-users] Understanding OptimizerScales in its entirety

[Wolf, Levin]

Hi everybody,

Nobody knows anything more detailed about the optimizerScales? 
Everything I've found are lots of diffenrent ways to set the Scales...


Thanks a lot

Levin
________________________________________
Von: insight-users-bounces at itk.org [insight-users-bounces at itk.org] im Auftrag von Wolf, Levin [Levin.Wolf at haw-hamburg.de]
Gesendet: Freitag, 12. August 2011 02:09
An: insight-users at itk.org
Betreff: [Insight-users] Understanding OptimizerScales in its entirety

Hi everybody,

i´m working on an 3D multisresolution Mutual Information registration and i would really like to understand the mechanism of the OptimizerScales in its entirety.
I know, why I need them and how to use them. But I´m still not able to retrace the way of my scaling. How are they really working...

In my case, I´m using:

itk::MattesMutualInformationImageToImageMetric
itk::VersorRigid3DTransform
itk::VersorRigid3DTransformOptimizer
itk::CenteredTransformInitializer

and for example  the following settings:


typedef OptimizerType::ScalesType       OptimizerScalesType;
  OptimizerScalesType optimizerScales( transform->GetNumberOfParameters() );
  const double translationScale = 1.0 / 2000.0;

  optimizerScales[0] = 1.0;
  optimizerScales[1] = 1.0;
  optimizerScales[2] = 1.0;
  optimizerScales[3] = translationScale;
  optimizerScales[4] = translationScale;
  optimizerScales[5] = translationScale;



    if ( registration->GetCurrentLevel() == 0 )
      {
      optimizer->SetMaximumStepLength( 8.0 );
      optimizer->SetMinimumStepLength( 1.0 );
      }
    else
      {
      optimizer->SetMaximumStepLength( optimizer->GetCurrentStepLength() / 2.0);
      optimizer->SetMinimumStepLength( optimizer->GetMinimumStepLength() / 10.0 );
      }

What happens to the Scales??? Are they getting normalized somehow? Or is the steplength simply devided by the Scale?

So how big would my first step be with these settings?


I would be very grateful if someone could help me to understand the inside of the scaling.



Thanks a lot

Levin





_____________________________________
Powered by www.kitware.com

Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html

Kitware offers ITK Training Courses, for more information visit:
http://www.kitware.com/products/protraining.html

Please keep messages on-topic and check the ITK FAQ at:
http://www.itk.org/Wiki/ITK_FAQ

Follow this link to subscribe/unsubscribe:
http://www.itk.org/mailman/listinfo/insight-users