vtk-m/vtkm/filter/MIRFilter.h

//============================================================================
//  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 vtkm_m_filter_MIRFilter_h
#define vtkm_m_filter_MIRFilter_h

#include <vtkm/cont/ArrayCopy.h>
#include <vtkm/cont/ArrayHandlePermutation.h>

#include <vtkm/filter/FilterDataSet.h>
#include <vtkm/filter/FilterDataSetWithField.h>

namespace vtkm
{
namespace filter
{
/// @brief Calculates and subdivides a mesh based on the material interface reconstruction algorithm.
///
/// Subdivides a mesh given volume fraction information for each _cell_. It does this by applying a
///     mixture of the painters algorithm and isosurfacing algorithm. This filter will return
///     a dataset where cells are subdivided into new cells of a certain "Material", and fields passed
///     will do 1 of 3 things:
///     1) They will not pass if they are an array associated with the whole mesh,
///     2) They will simply be passed to new cells if the array is associated with the cell set
///     3) They will be interpolated to new point locations if the array is associated with the point set
///
/// This algorithm requires passing a cell set of volume fraction information, not a point cell set.
///     The exact fields are required:
///     1) A length cell set that specifies the number of materials associated to the cell.
///     2) A position cell set (or offset cell set) that specifies where the material IDs and VFs occur in the ID and VF arrays.
///     3) An ID array (whole array set) that stores the material ID information
///     4) An VF array (whole array set) that stores the fractional volume information for the respective material ID.
///     Note that the cell VF information should add up to 1.0 across all materials for the cell, however this isn't checked in the code and might
///     lead to undesirable results when iterating.
///
/// Note that this algorithm does not guarantee that the newly constructed cells will match the provided
///     volume fractions, nor does it guarantee that there will exist a subcell of every material ID from the original cell.
///     This usually occurs when the resolution of the mesh is too low (isolated materials in a single cell).
///
/// If wanted, this algorithm can iterate, adjusting cell VFs based on distance from the target values and the previous calculated iteration.
///     This is done by setting the max iterations >0. In addition, the max percent error will allow for the filter to return early if the
///     total error % of the entire dataset is less than the specified amount (defaults to 1.0, returns after first iteration). Finally,
///     the error scaling and scaling decay allows for setting how much the cell VFs should react to the delta between target and calculated cell VFs.
///     the error scaling will decay by the decay variable every iteration (multiplicitively).
class MIRFilter : public vtkm::filter::FilterDataSet<MIRFilter>
{
public:
  /// @brief Sets the name of the offset/position cellset field in the dataset passed to the filter
  VTKM_CONT void SetPositionCellSetName(std::string name) { this->pos_name = name; }
  /// @brief Sets the name of the length cellset field in the dataset passed to the filter
  VTKM_CONT void SetLengthCellSetName(std::string name) { this->len_name = name; }
  /// @brief Sets the name of the ID whole-array set field in the dataset passed to the filter
  VTKM_CONT void SetIDWholeSetName(std::string name) { this->id_name = name; }
  /// @brief Sets the name of the VF whole-array set field in the dataset passed to the filter
  VTKM_CONT void SetVFWholeSetName(std::string name) { this->vf_name = name; }
  VTKM_CONT void SetMaxPercentError(vtkm::Float64 ma) { this->max_error = ma; }
  VTKM_CONT void SetMaxIterations(vtkm::IdComponent ma) { this->max_iter = ma; }
  VTKM_CONT void SetErrorScaling(vtkm::Float64 sc) { this->error_scaling = sc; }
  VTKM_CONT void SetScalingDecay(vtkm::Float64 sc) { this->scaling_decay = sc; }
  /// @brief Gets the output cell-set field name for the filter
  VTKM_CONT std::string GetOutputFieldName() { return this->OutputFieldName; }
  /// @brief Sets the output cell-set field name for the filter
  VTKM_CONT void SetOutputFieldName(std::string name) { this->OutputFieldName = name; }

  template <typename DerivedPolicy>
  VTKM_CONT vtkm::cont::DataSet DoExecute(const vtkm::cont::DataSet& input,
                                          vtkm::filter::PolicyBase<DerivedPolicy>);

  template <typename T, typename StorageType, typename DerivedPolicy>
  VTKM_CONT bool DoMapField(vtkm::cont::DataSet& result,
                            const vtkm::cont::ArrayHandle<T, StorageType>& input1,
                            const vtkm::filter::FieldMetadata& fieldMeta,
                            vtkm::filter::PolicyBase<DerivedPolicy>)
  {
    (void)result;
    (void)input1;
    (void)fieldMeta;

    if (fieldMeta.GetName().compare(this->pos_name) == 0 ||
        fieldMeta.GetName().compare(this->len_name) == 0 ||
        fieldMeta.GetName().compare(this->id_name) == 0 ||
        fieldMeta.GetName().compare(this->vf_name) == 0)
    {
      // Remember, we will map the field manually...
      // Technically, this will be for all of them...thus ignore it
      return false;
    }
    vtkm::cont::ArrayHandle<T> output;
    if (fieldMeta.IsPointField())
    {
      this->ProcessPointField(input1, output);
    }
    else if (fieldMeta.IsCellField())
    {
      this->ProcessCellField(input1, output);
    }
    else
    {
      return false;
    }
    result.AddField(fieldMeta.AsField(output));
    return true;
  }

private:
  // Linear storage requirement, scales with size of point output
  template <typename T, typename StorageType, typename StorageType2>
  VTKM_CONT void ProcessPointField(const vtkm::cont::ArrayHandle<T, StorageType>& input,
                                   vtkm::cont::ArrayHandle<T, StorageType2>& output);

  // NOTE: The below assumes that MIR will not change the cell values when subdividing.
  template <typename T, typename StorageType, typename StorageType2>
  VTKM_CONT void ProcessCellField(const vtkm::cont::ArrayHandle<T, StorageType>& input,
                                  vtkm::cont::ArrayHandle<T, StorageType2>& output)
  {
    // Use a temporary permutation array to simplify the mapping:
    auto tmp = vtkm::cont::make_ArrayHandlePermutation(this->filterCellInterp, input);
    vtkm::cont::ArrayCopy(tmp, output);
  }

  std::string pos_name;
  std::string len_name;
  std::string id_name;
  std::string vf_name;
  std::string OutputFieldName = std::string("cellMat");
  vtkm::Float64 max_error = vtkm::Float64(1.0);
  vtkm::Float64 scaling_decay = vtkm::Float64(1.0);
  vtkm::IdComponent max_iter = vtkm::IdComponent(0);
  vtkm::Float64 error_scaling = vtkm::Float64(0.0);
  vtkm::cont::ArrayHandle<vtkm::Id> filterCellInterp;
  vtkm::cont::ArrayHandle<vtkm::Vec<vtkm::Float64, 8>> MIRWeights;
  vtkm::cont::ArrayHandle<vtkm::Vec<vtkm::Id, 8>> MIRIDs;
};
}

}

#ifndef vtk_m_filter_MIRFilter_hxx
#include <vtkm/filter/MIRFilter.hxx>
#endif

#endif