/*=========================================================================
 *
 *  Copyright UMC Utrecht and contributors
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkElasticBodySplineKernelTransform2.txx,v $
  Date:      $Date: 2004/12/12 22:05:02 $
  Version:   $Revision: 1.20 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/
#ifndef _itkElasticBodySplineKernelTransform2_hxx
#define _itkElasticBodySplineKernelTransform2_hxx

#include "itkElasticBodySplineKernelTransform2.h"

namespace itk
{

template <typename TScalarType, unsigned int NDimensions>
ElasticBodySplineKernelTransform2<TScalarType, NDimensions>::ElasticBodySplineKernelTransform2()
{
  this->m_Alpha = 12.0 * (1.0 - .25) - 1.0;
}


template <typename TScalarType, unsigned int NDimensions>
void
ElasticBodySplineKernelTransform2<TScalarType, NDimensions>::ComputeG(const InputVectorType & x,
                                                                      GMatrixType &           GMatrix) const
{
  const TScalarType r = x.GetNorm();
  const TScalarType factor = -3.0 * r;
  const TScalarType radial = this->m_Alpha * r * r * r;
  for (unsigned int i = 0; i < NDimensions; ++i)
  {
    const typename InputVectorType::ValueType xi = x[i] * factor;
    // G is symmetric
    for (unsigned int j = 0; j < i; ++j)
    {
      const TScalarType value = xi * x[j];
      GMatrix[i][j] = value;
      GMatrix[j][i] = value;
    }
    GMatrix[i][i] = radial + xi * x[i];
  }

} // end ComputeG()


template <typename TScalarType, unsigned int NDimensions>
void
ElasticBodySplineKernelTransform2<TScalarType, NDimensions>::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);
  os << indent << "m_Alpha: " << this->m_Alpha << std::endl;

} // end PrintSelf()


} // namespace itk

#endif
