/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkWendlandQuinticKernel.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/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 notice for more information.

=========================================================================*/
// .NAME vtkWendlandQuinticKernel - a quintic SPH interpolation kernel

// .SECTION Description
// vtkWendlandQuinticKernel is an smooth particle hydrodynamics interpolation kernel as
// described by D.J. Price. This is a quintic formulation.
//
// .SECTION Caveats
// FOr more information see D.J. Price, Smoothed particle hydrodynamics and
// magnetohydrodynamics, J. Comput. Phys. 231:759-794, 2012. Especially
// equation 49.

// .SECTION Acknowledgments
// The following work has been generously supported by Altair Engineering
// and FluiDyna GmbH. Please contact Steve Cosgrove or Milos Stanic for
// more information.

// .SECTION See Also
// vtkSPHKernel vtkSPHInterpolator


#ifndef vtkWendlandQuinticKernel_h
#define vtkWendlandQuinticKernel_h

#include "vtkFiltersPointsModule.h" // For export macro
#include "vtkSPHKernel.h"
#include <algorithm> // For std::min()

class vtkIdList;
class vtkDoubleArray;


class VTKFILTERSPOINTS_EXPORT vtkWendlandQuinticKernel : public vtkSPHKernel
{
public:
  // Description:
  // Standard methods for instantiation, obtaining type information, and printing.
  static vtkWendlandQuinticKernel *New();
  vtkTypeMacro(vtkWendlandQuinticKernel,vtkSPHKernel);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Produce the computational parameters for the kernel. Invoke this method
  // after setting initial values like SpatialStep.
  virtual void Initialize(vtkAbstractPointLocator *loc, vtkDataSet *ds,
                          vtkPointData *pd);

  // Description:
  // Compute weighting factor given a normalized distance from a sample point.
  // Note that the formulation is slightly different to avoid an extra operation
  // (which has the effect of affecting the NormFactor by 1/16).
  virtual double ComputeFunctionWeight(const double d)
  {
    if ( d >= 2.0 )
      {
      return 0.0;
      }
    else
      {
      double tmp = 1.0 - 0.5*d;
      return (tmp*tmp*tmp*tmp) * (1.0 + 2.0*d);
      }
  }

  // Description:
  // Compute weighting factor for derivative quantities given a normalized
  // distance from a sample point.
  virtual double ComputeDerivWeight(const double d)
  {
    if ( d >= 2.0 )
      {
      return 0.0;
      }
    else
      {
      double tmp = 1.0 - 0.5*d;
      return -2.0*(tmp*tmp*tmp) * (1.0 + 2.0*d) +
        2.0*(tmp*tmp*tmp*tmp);
      }
  }

protected:
  vtkWendlandQuinticKernel();
  ~vtkWendlandQuinticKernel();

private:
  vtkWendlandQuinticKernel(const vtkWendlandQuinticKernel&) VTK_DELETE_FUNCTION;
  void operator=(const vtkWendlandQuinticKernel&) VTK_DELETE_FUNCTION;
};

#endif
