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121 lines
4.1 KiB
C++
121 lines
4.1 KiB
C++
/*=========================================================================
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Program: Visualization Toolkit
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Module: vtkSobelGradientMagnitudePass.h
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Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
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All rights reserved.
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See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
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This software is distributed WITHOUT ANY WARRANTY; without even
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the above copyright notice for more information.
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=========================================================================*/
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/**
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* @class vtkSobelGradientMagnitudePass
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* @brief Implement a post-processing edge
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* detection with a Sobel gradient magnitude render pass.
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*
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* Detect the edges of the image renderered by its delegate. Edge-detection
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* uses a Sobel high-pass filter (3x3 kernel).
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*
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* This pass expects an initialized depth buffer and color buffer.
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* Initialized buffers means they have been cleared with farest z-value and
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* background color/gradient/transparent color.
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* An opaque pass may have been performed right after the initialization.
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*
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* The delegate is used once.
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*
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* Its delegate is usually set to a vtkCameraPass or to a post-processing pass.
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*
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* This pass requires a OpenGL context that supports texture objects (TO),
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* framebuffer objects (FBO) and GLSL. If not, it will emit an error message
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* and will render its delegate and return.
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*
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* @par Implementation:
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* To compute the gradient magnitude, the x and y components of the gradient
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* (Gx and Gy) have to be computed first. Each computation of Gx and Gy uses
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* a separable filter.
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* The first pass takes the image from the delegate as the single input
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* texture.
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* The first pass has two outputs, one for the first part of Gx, Gx1, result of
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* a convolution with (-1 0 1), one for the first part of Gy, Gy1, result of a
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* convolution with (1 2 1).
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* The second pass has two inputs, Gx1 and Gy1. Kernel (1 2 1)^T is applied
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* to Gx1 and kernel (-1 0 1)^T is applied to Gx2. It gives the values for
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* Gx and Gy. Those values are then used to compute the magnitude of the
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* gradient which is stored in the render target.
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* The gradient computation happens per component (R,G,B). A is arbitrarily set
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* to 1 (full opacity).
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*
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* @par Implementation:
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* \image html vtkSobelGradientMagnitudePassFigure.png
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* \image latex vtkSobelGradientMagnitudePassFigure.eps
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*
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* @sa
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* vtkRenderPass
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*/
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#ifndef vtkSobelGradientMagnitudePass_h
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#define vtkSobelGradientMagnitudePass_h
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#include "vtkImageProcessingPass.h"
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#include "vtkRenderingOpenGL2Module.h" // For export macro
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class vtkDepthPeelingPassLayerList; // Pimpl
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class vtkOpenGLFramebufferObject;
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class vtkOpenGLHelper;
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class vtkOpenGLRenderWindow;
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class vtkTextureObject;
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class VTKRENDERINGOPENGL2_EXPORT vtkSobelGradientMagnitudePass : public vtkImageProcessingPass
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{
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public:
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static vtkSobelGradientMagnitudePass* New();
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vtkTypeMacro(vtkSobelGradientMagnitudePass, vtkImageProcessingPass);
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void PrintSelf(ostream& os, vtkIndent indent) override;
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/**
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* Perform rendering according to a render state \p s.
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* \pre s_exists: s!=0
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*/
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void Render(const vtkRenderState* s) override;
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/**
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* Release graphics resources and ask components to release their own
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* resources.
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* \pre w_exists: w!=0
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*/
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void ReleaseGraphicsResources(vtkWindow* w) override;
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protected:
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/**
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* Default constructor. DelegatePass is set to NULL.
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*/
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vtkSobelGradientMagnitudePass();
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/**
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* Destructor.
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*/
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~vtkSobelGradientMagnitudePass() override;
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/**
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* Graphics resources.
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*/
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vtkOpenGLFramebufferObject* FrameBufferObject;
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vtkTextureObject* Pass1; // render target for the scene
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vtkTextureObject* Gx1; // render target 0 for the first shader
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vtkTextureObject* Gy1; // render target 1 for the first shader
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// Structures for the various cell types we render.
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vtkOpenGLHelper* Program1; // shader to compute Gx1 and Gy1
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vtkOpenGLHelper* Program2; // shader to compute |G| from Gx1 and Gy1
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private:
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vtkSobelGradientMagnitudePass(const vtkSobelGradientMagnitudePass&) = delete;
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void operator=(const vtkSobelGradientMagnitudePass&) = delete;
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};
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#endif
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