vtkLineIntegralConvolution2D Class Reference

#include <vtkLineIntegralConvolution2D.h>

Inheritance diagram for vtkLineIntegralConvolution2D:

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Collaboration diagram for vtkLineIntegralConvolution2D:

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List of all members.

Detailed Description

GPU-based implementation of Line Integral Convolution (LIC).

This class resorts to GLSL to implement GPU-based Line Integral Convolution (LIC) for visualizing a 2D vector field that may be obtained by projecting an original 3D vector field onto a surface (such that the resulting 2D vector at each grid point on the surface is tangential to the local normal, as done in vtkSurfaceLICPainter).

As an image-based technique, 2D LIC works by (1) integrating a bidirectional streamline from the center of each pixel (of the LIC output image), (2) locating the pixels along / hit by this streamline as the correlated pixels of the starting pixel (seed point / pixel), (3) indexing a (usually white) noise texture (another input to LIC, in addition to the 2D vector field, usually with the same size as that of the 2D vetor field) to determine the values (colors) of these pixels (the starting and the correlated pixels), typically through bi-linear interpolation, and (4) performing convolution (weighted averaging) on these values, by adopting a low-pass filter (such as box, ramp, and Hanning kernels), to obtain the result value (color) that is then assigned to the seed pixel.

The GLSL-based GPU implementation herein maps the aforementioned pipeline to fragment shaders and a box kernel is employed. Both the white noise and the vector field are provided to the GPU as texture objects (supported by the multi-texturing capability). In addition, there are four texture objects (color buffers) allocated to constitute two pairs that work in a ping-pong fashion, with one as the read buffers and the other as the write / render targets. Maintained by a frame buffer object (GL_EXT_framebuffer_object), each pair employs one buffer to store the current (dynamically updated) position (by means of the texture coordinate that keeps being warped by the underlying vector) of the (virtual) particle initially released from each fragment while using the bother buffer to store the current (dynamically updated too) accumulated texture value that each seed fragment (before the 'mesh' is warped) collects. Given NumberOfSteps integration steps in each direction, there are a total of (2 * NumberOfSteps + 1) fragments (including the seed fragment) are convolved and each contributes 1 / (2 * NumberOfSteps + 1) of the associated texture value to fulfill the box filter.

One pass of LIC (basic LIC) tends to produce low-contrast / blurred images and vtkLineIntegralConvolution2D provides an option for creating enhanced LIC images. Enhanced LIC improves image quality by increasing inter-streamline contrast while suppressing artifacts. It performs two passes of LIC, with a 3x3 Laplacian high-pass filter in between that processes the output of pass #1 LIC and forwards the result as the input 'noise' to pass #2 LIC. Enhanced LIC automatically degenerates to basic LIC during user interaction.

vtkLineIntegralConvolution2D applies masking to zero-vector fragments so that un-filtered white noise areas are made totally transparent by class vtkSurfaceLICPainter to show the underlying geometry surface.

Required OpenGL Extensins:: GL_ARB_texture_non_power_of_two GL_VERSION_2_0 GL_ARB_texture_float GL_ARB_draw_buffers GL_EXT_framebuffer_object

See also:: vtkSurfaceLICPainter vtkImageDataLIC2D vtkStructuredGridLIC2D

Definition at line 86 of file vtkLineIntegralConvolution2D.h.


Public Types
typedef vtkObject	Superclass
Public Member Functions
virtual const char *	GetClassName ()
virtual int	IsA (const char *type)
void	PrintSelf (ostream &os, vtkIndent indent)
int	Execute ()

virtual void	SetEnhancedLIC (int)
virtual int	GetEnhancedLIC ()
virtual void	EnhancedLICOn ()
virtual void	EnhancedLICOff ()

virtual void	SetLICForSurface (int)
virtual int	GetLICForSurface ()
virtual void	LICForSurfaceOn ()
virtual void	LICForSurfaceOff ()

virtual void	SetNumberOfSteps (int)
virtual int	GetNumberOfSteps ()

virtual void	SetLICStepSize (double)
virtual double	GetLICStepSize ()

void	SetNoise (vtkTextureObject *noise)
virtual vtkTextureObject *	GetNoise ()

void	SetVectorField (vtkTextureObject *vectorField)
virtual vtkTextureObject *	GetVectorField ()

virtual void	SetComponentIds (int, int)
void	SetComponentIds (int[2])
virtual int *	GetComponentIds ()
virtual void	GetComponentIds (int &, int &)
virtual void	GetComponentIds (int[2])

virtual void	SetGridSpacings (double, double)
void	SetGridSpacings (double[2])
virtual double *	GetGridSpacings ()
virtual void	GetGridSpacings (double &, double &)
virtual void	GetGridSpacings (double[2])

virtual void	SetTransformVectors (int)
virtual void	TransformVectorsOn ()
virtual void	TransformVectorsOff ()
virtual int	GetTransformVectors ()

virtual void	SetMagnification (int)
virtual int	GetMagnification ()

void	SetVectorShiftScale (double shift, double scale)

int	Execute (unsigned int extent[4])
int	Execute (int extent[4])

void	SetLIC (vtkTextureObject *lic)
virtual vtkTextureObject *	GetLIC ()
Static Public Member Functions
static vtkLineIntegralConvolution2D *	New ()
static int	IsTypeOf (const char *type)
static vtkLineIntegralConvolution2D *	SafeDownCast (vtkObject *o)
static bool	IsSupported (vtkRenderWindow *renWin)
Protected Member Functions
	vtkLineIntegralConvolution2D ()
	~vtkLineIntegralConvolution2D ()
Protected Attributes
int	Magnification
int	NumberOfSteps
int	LICForSurface
int	EnhancedLIC
double	LICStepSize
double	VectorShift
double	VectorScale
int	TransformVectors
int	ComponentIds [2]
double	GridSpacings [2]
vtkTextureObject *	VectorField
vtkTextureObject *	Noise
vtkTextureObject *	LIC

Member Typedef Documentation

typedef vtkObject vtkLineIntegralConvolution2D::Superclass

Reimplemented from vtkObject.

Definition at line 91 of file vtkLineIntegralConvolution2D.h.

Constructor & Destructor Documentation

vtkLineIntegralConvolution2D::vtkLineIntegralConvolution2D ( ) [protected]

vtkLineIntegralConvolution2D::~vtkLineIntegralConvolution2D ( ) [protected]

Member Function Documentation

static vtkLineIntegralConvolution2D* vtkLineIntegralConvolution2D::New ( ) [static]

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

Reimplemented from vtkObject.

virtual const char* vtkLineIntegralConvolution2D::GetClassName ( ) [virtual]

Reimplemented from vtkObject.

static int vtkLineIntegralConvolution2D::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 vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkObject.

virtual int vtkLineIntegralConvolution2D::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 vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkObject.

static vtkLineIntegralConvolution2D* vtkLineIntegralConvolution2D::SafeDownCast ( vtkObject * o ) [static]

Reimplemented from vtkObject.

void vtkLineIntegralConvolution2D::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 vtkObject.

virtual void vtkLineIntegralConvolution2D::SetEnhancedLIC ( int ) [virtual]

Enable/Disable enhanced LIC that improves image quality by increasing inter-streamline contrast while suppressing artifacts. Enhanced LIC performs two passes of LIC, with a 3x3 Laplacian high-pass filter in between that processes the output of pass #1 LIC and forwards the result as the input 'noise' to pass #2 LIC. This flag is automatically turned off during user interaction.

virtual int vtkLineIntegralConvolution2D::GetEnhancedLIC ( ) [virtual]

Enable/Disable enhanced LIC that improves image quality by increasing inter-streamline contrast while suppressing artifacts. Enhanced LIC performs two passes of LIC, with a 3x3 Laplacian high-pass filter in between that processes the output of pass #1 LIC and forwards the result as the input 'noise' to pass #2 LIC. This flag is automatically turned off during user interaction.

virtual void vtkLineIntegralConvolution2D::EnhancedLICOn ( ) [virtual]

Enable/Disable enhanced LIC that improves image quality by increasing inter-streamline contrast while suppressing artifacts. Enhanced LIC performs two passes of LIC, with a 3x3 Laplacian high-pass filter in between that processes the output of pass #1 LIC and forwards the result as the input 'noise' to pass #2 LIC. This flag is automatically turned off during user interaction.

virtual void vtkLineIntegralConvolution2D::EnhancedLICOff ( ) [virtual]

Enable/Disable enhanced LIC that improves image quality by increasing inter-streamline contrast while suppressing artifacts. Enhanced LIC performs two passes of LIC, with a 3x3 Laplacian high-pass filter in between that processes the output of pass #1 LIC and forwards the result as the input 'noise' to pass #2 LIC. This flag is automatically turned off during user interaction.

virtual void vtkLineIntegralConvolution2D::SetLICForSurface ( int ) [virtual]

Enable/Disable LICForSurface, for which the LIC texture is composited with the underlying geometry.

virtual int vtkLineIntegralConvolution2D::GetLICForSurface ( ) [virtual]

Enable/Disable LICForSurface, for which the LIC texture is composited with the underlying geometry.

virtual void vtkLineIntegralConvolution2D::LICForSurfaceOn ( ) [virtual]

Enable/Disable LICForSurface, for which the LIC texture is composited with the underlying geometry.

virtual void vtkLineIntegralConvolution2D::LICForSurfaceOff ( ) [virtual]

Enable/Disable LICForSurface, for which the LIC texture is composited with the underlying geometry.

virtual void vtkLineIntegralConvolution2D::SetNumberOfSteps ( int ) [virtual]

Number of streamline integration steps (initial value is 1). In term of visual quality, the greater (within some range) the better.

virtual int vtkLineIntegralConvolution2D::GetNumberOfSteps ( ) [virtual]

Number of streamline integration steps (initial value is 1). In term of visual quality, the greater (within some range) the better.

virtual void vtkLineIntegralConvolution2D::SetLICStepSize ( double ) [virtual]

Get/Set the streamline integration step size (0.01 by default). This is the length of each step in normalized image space i.e. in range [0, 1]. In term of visual quality, the smaller the better. The type for the interface is double as VTK interface is, but GPU only supports float. Thus it will be converted to float in the execution of the algorithm.

virtual double vtkLineIntegralConvolution2D::GetLICStepSize ( ) [virtual]

Get/Set the streamline integration step size (0.01 by default). This is the length of each step in normalized image space i.e. in range [0, 1]. In term of visual quality, the smaller the better. The type for the interface is double as VTK interface is, but GPU only supports float. Thus it will be converted to float in the execution of the algorithm.

void vtkLineIntegralConvolution2D::SetNoise ( vtkTextureObject * noise )

Set/Get the input white noise texture (initial value is NULL).

virtual vtkTextureObject* vtkLineIntegralConvolution2D::GetNoise ( ) [virtual]

Set/Get the input white noise texture (initial value is NULL).

void vtkLineIntegralConvolution2D::SetVectorField ( vtkTextureObject * vectorField )

Set/Get the vector field (initial value is NULL).

virtual vtkTextureObject* vtkLineIntegralConvolution2D::GetVectorField ( ) [virtual]

Set/Get the vector field (initial value is NULL).

virtual void vtkLineIntegralConvolution2D::SetComponentIds	(	int	,
		int
	)			`[virtual]`