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vtkFiniteDifferenceGradientEstimator.h
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vtkFiniteDifferenceGradientEstimator.h
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/*=========================================================================
Program: Visualization Toolkit
Module: vtkFiniteDifferenceGradientEstimator.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.
=========================================================================*/
/**
* @class vtkFiniteDifferenceGradientEstimator
* @brief Use finite differences to estimate gradient.
*
*
* vtkFiniteDifferenceGradientEstimator is a concrete subclass of
* vtkEncodedGradientEstimator that uses a central differences technique to
* estimate the gradient. The gradient at some sample location (x,y,z)
* would be estimated by:
*
* nx = (f(x-dx,y,z) - f(x+dx,y,z)) / 2*dx;
* ny = (f(x,y-dy,z) - f(x,y+dy,z)) / 2*dy;
* nz = (f(x,y,z-dz) - f(x,y,z+dz)) / 2*dz;
*
* This value is normalized to determine a unit direction vector and a
* magnitude. The normal is computed in voxel space, and
* dx = dy = dz = SampleSpacingInVoxels. A scaling factor is applied to
* convert this normal from voxel space to world coordinates.
*
* @sa
* vtkEncodedGradientEstimator
*/
#ifndef vtkFiniteDifferenceGradientEstimator_h
#define vtkFiniteDifferenceGradientEstimator_h
#include "vtkRenderingVolumeModule.h" // For export macro
#include "vtkEncodedGradientEstimator.h"
class VTKRENDERINGVOLUME_EXPORT vtkFiniteDifferenceGradientEstimator : public vtkEncodedGradientEstimator
{
public:
vtkTypeMacro(vtkFiniteDifferenceGradientEstimator,vtkEncodedGradientEstimator);
void PrintSelf( ostream& os, vtkIndent indent ) override;
/**
* Construct a vtkFiniteDifferenceGradientEstimator with
* a SampleSpacingInVoxels of 1.
*/
static vtkFiniteDifferenceGradientEstimator *New();
//@{
/**
* Set/Get the spacing between samples for the finite differences
* method used to compute the normal. This spacing is in voxel units.
*/
vtkSetMacro( SampleSpacingInVoxels, int );
vtkGetMacro( SampleSpacingInVoxels, int );
//@}
// The sample spacing between samples taken for the normal estimation
int SampleSpacingInVoxels;
protected:
vtkFiniteDifferenceGradientEstimator();
~vtkFiniteDifferenceGradientEstimator() override;
/**
* Recompute the encoded normals and gradient magnitudes.
*/
void UpdateNormals( void ) override;
private:
vtkFiniteDifferenceGradientEstimator(const vtkFiniteDifferenceGradientEstimator&) = delete;
void operator=(const vtkFiniteDifferenceGradientEstimator&) = delete;
};
#endif