vtkSobelGradientMagnitudePass Class Reference

#include <vtkSobelGradientMagnitudePass.h>

Inheritance diagram for vtkSobelGradientMagnitudePass:

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Collaboration diagram for vtkSobelGradientMagnitudePass:

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List of all members.

Detailed Description

Implement a post-processing edge detection with a Sobel gradient magnitude render pass.

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.

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).

Implementation:

See also:: vtkRenderPass

Tests:: vtkSobelGradientMagnitudePass (Tests)

Definition at line 74 of file vtkSobelGradientMagnitudePass.h.


Public Types
typedef vtkRenderPass	Superclass
Public Member Functions
virtual const char *	GetClassName ()
virtual int	IsA (const char *type)
void	PrintSelf (ostream &os, vtkIndent indent)
virtual void	Render (const vtkRenderState *s)
void	ReleaseGraphicsResources (vtkWindow *w)

virtual vtkRenderPass *	GetDelegatePass ()
virtual void	SetDelegatePass (vtkRenderPass *delegatePass)
Static Public Member Functions
static vtkSobelGradientMagnitudePass *	New ()
static int	IsTypeOf (const char *type)
static vtkSobelGradientMagnitudePass *	SafeDownCast (vtkObject *o)
Protected Member Functions
	vtkSobelGradientMagnitudePass ()
virtual	~vtkSobelGradientMagnitudePass ()
Protected Attributes
vtkRenderPass *	DelegatePass

vtkFrameBufferObject *	FrameBufferObject
vtkTextureObject *	Pass1
vtkTextureObject *	Gx1
vtkTextureObject *	Gy1
vtkShaderProgram2 *	Program1
vtkShaderProgram2 *	Program2

Member Typedef Documentation

typedef vtkRenderPass vtkSobelGradientMagnitudePass::Superclass

Reimplemented from vtkRenderPass.

Definition at line 78 of file vtkSobelGradientMagnitudePass.h.

Constructor & Destructor Documentation

vtkSobelGradientMagnitudePass::vtkSobelGradientMagnitudePass ( ) [protected]

Default constructor. DelegatePass is set to NULL.

virtual vtkSobelGradientMagnitudePass::~vtkSobelGradientMagnitudePass ( ) [protected, virtual]

Destructor.

Member Function Documentation

static vtkSobelGradientMagnitudePass* vtkSobelGradientMagnitudePass::New ( ) [static]

Create an object with Debug turned off, modified time initialized to zero, and reference counting on.

Reimplemented from vtkObject.

virtual const char* vtkSobelGradientMagnitudePass::GetClassName ( ) [virtual]

Reimplemented from vtkRenderPass.

static int vtkSobelGradientMagnitudePass::IsTypeOf ( const char * name ) [static]

Return 1 if this class type is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkRenderPass.

virtual int vtkSobelGradientMagnitudePass::IsA ( const char * name ) [virtual]

Return 1 if this class is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkRenderPass.

static vtkSobelGradientMagnitudePass* vtkSobelGradientMagnitudePass::SafeDownCast ( vtkObject * o ) [static]

Reimplemented from vtkRenderPass.

void vtkSobelGradientMagnitudePass::PrintSelf	(	ostream &	os,
		vtkIndent	indent
	)			`[virtual]`

Methods invoked by print to print information about the object including superclasses. Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.

Reimplemented from vtkRenderPass.

virtual void vtkSobelGradientMagnitudePass::Render ( const vtkRenderState * s ) [virtual]

Perform rendering according to a render state s.

Precondition:: s_exists: s!=0

Implements vtkRenderPass.

void vtkSobelGradientMagnitudePass::ReleaseGraphicsResources ( vtkWindow * w ) [virtual]

Release graphics resources and ask components to release their own resources.

Precondition:: w_exists: w!=0

Reimplemented from vtkRenderPass.

virtual vtkRenderPass* vtkSobelGradientMagnitudePass::GetDelegatePass ( ) [virtual]

Delegate for rendering the image to be blurred. If it is NULL, nothing will be rendered and a warning will be emitted. It is usually set to a vtkCameraPass or to a post-processing pass. Initial value is a NULL pointer.

virtual void vtkSobelGradientMagnitudePass::SetDelegatePass ( vtkRenderPass * delegatePass ) [virtual]

Delegate for rendering the image to be blurred. If it is NULL, nothing will be rendered and a warning will be emitted. It is usually set to a vtkCameraPass or to a post-processing pass. Initial value is a NULL pointer.