text: //============================================================================
  //  Copyright (c) Kitware, Inc.
  //  All rights reserved.
  //  See LICENSE.txt 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.
  //============================================================================
  #ifndef vtk_m_filter_ClipWithImplicitFunction_h
  #define vtk_m_filter_ClipWithImplicitFunction_h
  
  #include <vtkm/filter/vtkm_filter_extra_export.h>
  
  #include <vtkm/cont/ImplicitFunctionHandle.h>
  #include <vtkm/filter/FilterDataSet.h>
  #include <vtkm/filter/MapFieldPermutation.h>
  #include <vtkm/worklet/Clip.h>
  
  namespace vtkm
  {
  namespace filter
  {
  
  /// \brief Clip a dataset using an implicit function
  ///
  /// Clip a dataset using a given implicit function value, such as vtkm::Sphere
  /// or vtkm::Frustum.
  /// The resulting geometry will not be water tight.
  class VTKM_ALWAYS_EXPORT ClipWithImplicitFunction
    : public vtkm::filter::FilterDataSet<ClipWithImplicitFunction>
  {
  public:
    void SetImplicitFunction(const vtkm::cont::ImplicitFunctionHandle& func)
    {
      this->Function = func;
    }
  
    void SetInvertClip(bool invert) { this->Invert = invert; }
  
    const vtkm::cont::ImplicitFunctionHandle& GetImplicitFunction() const { return this->Function; }
  
    template <typename DerivedPolicy>
    vtkm::cont::DataSet DoExecute(const vtkm::cont::DataSet& input,
                                  vtkm::filter::PolicyBase<DerivedPolicy> policy);
  
    template <typename DerivedPolicy>
    VTKM_CONT bool MapFieldOntoOutput(vtkm::cont::DataSet& result,
                                      const vtkm::cont::Field& field,
                                      vtkm::filter::PolicyBase<DerivedPolicy> policy)
    {
      if (field.IsFieldPoint())
      {
        // If the field is a point field, then we need to do a custom interpolation of the points.
        // In this case, we need to call the superclass's MapFieldOntoOutput, which will in turn
        // call our DoMapField.
        return this->FilterDataSet<ClipWithImplicitFunction>::MapFieldOntoOutput(
          result, field, policy);
      }
      else if (field.IsFieldCell())
      {
        // Use the precompiled field permutation function.
        vtkm::cont::ArrayHandle<vtkm::Id> permutation = this->Worklet.GetCellMapOutputToInput();
        return vtkm::filter::MapFieldPermutation(field, permutation, result);
      }
      else if (field.IsFieldGlobal())
      {
        result.AddField(field);
        return true;
      }
      else
      {
        return false;
      }
    }
  
    //Map a new field onto the resulting dataset after running the filter.
    //This call is only valid after Execute has been called.
    template <typename T, typename StorageType, typename DerivedPolicy>
    bool DoMapField(vtkm::cont::DataSet& result,
                    const vtkm::cont::ArrayHandle<T, StorageType>& input,
                    const vtkm::filter::FieldMetadata& fieldMeta,
                    vtkm::filter::PolicyBase<DerivedPolicy>)
    {
      // All other conditions should be handled by MapFieldOntoOutput directly.
      VTKM_ASSERT(fieldMeta.IsPointField());
  
      vtkm::cont::ArrayHandle<T> output;
      output = this->Worklet.ProcessPointField(input);
  
      //use the same meta data as the input so we get the same field name, etc.
      result.AddField(fieldMeta.AsField(output));
      return true;
    }
  
  private:
    vtkm::cont::ImplicitFunctionHandle Function;
    vtkm::worklet::Clip Worklet;
    bool Invert = false;
  };
  
  #ifndef vtkm_filter_ClipWithImplicitFunction_cxx
  VTKM_FILTER_EXPORT_EXECUTE_METHOD(ClipWithImplicitFunction);
  #endif
  }
  } // namespace vtkm::filter
  
  #ifndef vtk_m_filter_ClipWithImplicitFunction_hxx
  #include <vtkm/filter/ClipWithImplicitFunction.hxx>
  #endif
  
  #endif // vtk_m_filter_ClipWithImplicitFunction_h
  