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/*=========================================================================
Program: Visualization Toolkit
Module: vtkSobelGradientMagnitudePass.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.
=========================================================================*/
// .NAME vtkSobelGradientMagnitudePass - Implement a post-processing edge
// detection with a Sobel gradient magnitude render pass.
// .SECTION Description
// Detect the edges of the image renderered by its delegate. Edge-detection
// uses a Sobel high-pass filter (3x3 kernel).
//
// This pass expects an initialized depth buffer and color buffer.
// Initialized buffers means they have been cleared with farest z-value and
// background color/gradient/transparent color.
// An opaque pass may have been performed right after the initialization.
//
// The delegate is used once.
//
// Its delegate is usually set to a vtkCameraPass or to a post-processing pass.
//
// This pass requires a OpenGL context that supports texture objects (TO),
// framebuffer objects (FBO) and GLSL. If not, it will emit an error message
// and will render its delegate and return.
//
// .SECTION Implementation
// To compute the gradient magnitude, the x and y components of the gradient
// (Gx and Gy) have to be computed first. Each computation of Gx and Gy uses
// a separable filter.
// The first pass takes the image from the delegate as the single input
// texture.
// The first pass has two outputs, one for the first part of Gx, Gx1, result of
// a convolution with (-1 0 1), one for the first part of Gy, Gy1, result of a
// convolution with (1 2 1).
// The second pass has two inputs, Gx1 and Gy1. Kernel (1 2 1)^T is applied
// to Gx1 and kernel (-1 0 1)^T is applied to Gx2. It gives the values for
// Gx and Gy. Thoses values are then used to compute the magnitude of the
// gradient which is stored in the render target.
// The gradient computation happens per component (R,G,B). A is arbitrarly set
// to 1 (full opacity).
//
// \image html vtkSobelGradientMagnitudePassFigure.png
// \image latex vtkSobelGradientMagnitudePassFigure.eps
// .SECTION See Also
// vtkRenderPass
#ifndef vtkSobelGradientMagnitudePass_h
#define vtkSobelGradientMagnitudePass_h
#include "vtkRenderingOpenGLModule.h" // For export macro
#include "vtkImageProcessingPass.h"
class vtkOpenGLRenderWindow;
class vtkDepthPeelingPassLayerList; // Pimpl
class vtkShaderProgram2;
class vtkShader2;
class vtkFrameBufferObject;
class vtkTextureObject;
class VTKRENDERINGOPENGL_EXPORT vtkSobelGradientMagnitudePass : public vtkImageProcessingPass
{
public:
static vtkSobelGradientMagnitudePass *New();
vtkTypeMacro(vtkSobelGradientMagnitudePass,vtkImageProcessingPass);
void PrintSelf(ostream& os, vtkIndent indent);
//BTX
// Description:
// Perform rendering according to a render state \p s.
// \pre s_exists: s!=0
virtual void Render(const vtkRenderState *s);
//ETX
// Description:
// Release graphics resources and ask components to release their own
// resources.
// \pre w_exists: w!=0
void ReleaseGraphicsResources(vtkWindow *w);
protected:
// Description:
// Default constructor. DelegatePass is set to NULL.
vtkSobelGradientMagnitudePass();
// Description:
// Destructor.
virtual ~vtkSobelGradientMagnitudePass();
// Description:
// Graphics resources.
vtkFrameBufferObject *FrameBufferObject;
vtkTextureObject *Pass1; // render target for the scene
vtkTextureObject *Gx1; // render target 0 for the first shader
vtkTextureObject *Gy1; // render target 1 for the first shader
vtkShaderProgram2 *Program1; // shader to compute Gx1 and Gy1
vtkShaderProgram2 *Program2; // shader to compute |G| from Gx1 and Gy1
private:
vtkSobelGradientMagnitudePass(const vtkSobelGradientMagnitudePass&); // Not implemented.
void operator=(const vtkSobelGradientMagnitudePass&); // Not implemented.
};
#endif
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