// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
/**
 * @class   vtkLinearKernel
 * @brief   a linear interpolation kernel
 *
 *
 * vtkLinearKernel is an interpolation kernel that averages the contributions
 * of all points in the basis.
 *
 * @sa
 * vtkPointInterpolator vtkInterpolationKernel vtkGeneralizedKernel
 * vtkGaussianKernel vtkLinearKernel vtkShepardKernel
 */

#ifndef vtkLinearKernel_h
#define vtkLinearKernel_h

#include "vtkFiltersPointsModule.h" // For export macro
#include "vtkGeneralizedKernel.h"

VTK_ABI_NAMESPACE_BEGIN
class vtkIdList;
class vtkDoubleArray;

class VTKFILTERSPOINTS_EXPORT vtkLinearKernel : public vtkGeneralizedKernel
{
public:
  ///@{
  /**
   * Standard methods for instantiation, obtaining type information, and printing.
   */
  static vtkLinearKernel* New();
  vtkTypeMacro(vtkLinearKernel, vtkGeneralizedKernel);
  void PrintSelf(ostream& os, vtkIndent indent) override;
  ///@}

  // Reuse any superclass signatures that we don't override.
  using vtkGeneralizedKernel::ComputeWeights;

  /**
   * Given a point x, a list of basis points pIds, and a probability
   * weighting function prob, compute interpolation weights associated with
   * these basis points.  Note that basis points list pIds, the probability
   * weighting prob, and the weights array are provided by the caller of the
   * method, and may be dynamically resized as necessary. The method returns
   * the number of weights (pIds may be resized in some cases). Typically
   * this method is called after ComputeBasis(), although advanced users can
   * invoke ComputeWeights() and provide the interpolation basis points pIds
   * directly. The probably weighting prob are numbers 0<=prob<=1 which are
   * multiplied against the interpolation weights before normalization. They
   * are estimates of local confidence of weights. The prob may be nullptr in
   * which all probabilities are considered =1.
   */
  vtkIdType ComputeWeights(
    double x[3], vtkIdList* pIds, vtkDoubleArray* prob, vtkDoubleArray* weights) override;

protected:
  vtkLinearKernel();
  ~vtkLinearKernel() override;

private:
  vtkLinearKernel(const vtkLinearKernel&) = delete;
  void operator=(const vtkLinearKernel&) = delete;
};

VTK_ABI_NAMESPACE_END
#endif
