// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
/**
 * @class   vtkPerlinNoise
 * @brief   an implicit function that implements Perlin noise
 *
 * vtkPerlinNoise computes a Perlin noise field as an implicit function.
 * vtkPerlinNoise is a concrete implementation of vtkImplicitFunction.
 * Perlin noise, originally described by Ken Perlin, is a non-periodic and
 * continuous noise function useful for modeling real-world objects.
 *
 * The amplitude and frequency of the noise pattern are adjustable.  This
 * implementation of Perlin noise is derived closely from Greg Ward's version
 * in Graphics Gems II.
 *
 * @sa
 * vtkImplicitFunction
 */

#ifndef vtkPerlinNoise_h
#define vtkPerlinNoise_h

#include "vtkCommonDataModelModule.h" // For export macro
#include "vtkImplicitFunction.h"

VTK_ABI_NAMESPACE_BEGIN
class VTKCOMMONDATAMODEL_EXPORT vtkPerlinNoise : public vtkImplicitFunction
{
public:
  vtkTypeMacro(vtkPerlinNoise, vtkImplicitFunction);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  /**
   * Instantiate the class.
   */
  static vtkPerlinNoise* New();

  ///@{
  /**
   * Evaluate PerlinNoise function.
   */
  using vtkImplicitFunction::EvaluateFunction;
  double EvaluateFunction(double x[3]) override;
  ///@}

  /**
   * Evaluate PerlinNoise gradient.  Currently, the method returns a 0
   * gradient.
   */
  void EvaluateGradient(double x[3], double n[3]) override;

  ///@{
  /**
   * Set/get the frequency, or physical scale,  of the noise function
   * (higher is finer scale).  The frequency can be adjusted per axis, or
   * the same for all axes.
   */
  vtkSetVector3Macro(Frequency, double);
  vtkGetVectorMacro(Frequency, double, 3);
  ///@}

  ///@{
  /**
   * Set/get the phase of the noise function.  This parameter can be used to
   * shift the noise function within space (perhaps to avoid a beat with a
   * noise pattern at another scale).  Phase tends to repeat about every
   * unit, so a phase of 0.5 is a half-cycle shift.
   */
  vtkSetVector3Macro(Phase, double);
  vtkGetVectorMacro(Phase, double, 3);
  ///@}

  ///@{
  /**
   * Set/get the amplitude of the noise function. Amplitude can be negative.
   * The noise function varies randomly between -|Amplitude| and |Amplitude|.
   * Therefore the range of values is 2*|Amplitude| large.
   * The initial amplitude is 1.
   */
  vtkSetMacro(Amplitude, double);
  vtkGetMacro(Amplitude, double);
  ///@}

protected:
  vtkPerlinNoise();
  ~vtkPerlinNoise() override = default;

  double Frequency[3];
  double Phase[3];
  double Amplitude;

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

VTK_ABI_NAMESPACE_END
#endif
