A state-based OpenGL renderer for simple volume rendering. More...

#include <volumerenderer.h>

Inheritance diagram for VolumeRenderer:

Collaboration diagram for VolumeRenderer:

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Public Types
enum	ProjectionType { Perspective, Orthographic }

Public Slots
void	setLightParameters (float azimuth, float angle)
	Sets the light parameters. More...

void	lightDelta (float azimuth, float angle)
	\( \delta \)-form of setLightParameters which applies a change to the current values.

void	setRotation (float x, float y)

void	rotationDelta (float x, float y)

void	setDistance (float d)

void	distanceDelta (float d)

void	setRenderBoundingBox (bool b)

void	setFixSlicingMatrix (bool b)

void	setShowLightDirection (bool b)

void	setSliceDelta (float sliceDelta)

void	setProjectionType (ProjectionType pt)

void	setLowerWindowLimit (float w)

void	setUpperWindowLimit (float w)

void	setSmoothVolume (bool b)

void	setGaussianSigma (float s)

void	setApplyDOF (bool v)
	Toggles the depth-of-field effect on/off.

void	setFocalPlane (float d)
	Sets the distance to the focal plane, \( d \in [0,1]\). More...

void	setBlurAmount (float R)
	Sets the rate at which the blurring increases with distance to the focal plane. More...

Signals
void	distanceChanged (float d)
	Emitted when the camera distance is changed.

void	rotationChanged (float xRot, float yRot)
	Emitted when camera rotation is changed.

void	lightParamsChanged (float azimuth, float angle)
	Emitted when the light parameters changed.

void	requestDraw ()
	Emitted when the state of the renderer is changed in a way that would change the rendered image. More...

void	requestUpdate ()
	Like requestDraw, but requests that the window call update instead.

Public Member Functions
	VolumeRenderer (QObject *parent=nullptr)
	Sets up basic stuff. More...

QSurfaceFormat	getDesiredFormat () const
	Returns the surface format the renderer would like to have.

bool	initialize ()
	Initializes the volume renderer, using the currently bound OpenGL context. More...

const QString	error () const
	Returns the current error text of the renderer. More...

void	drawCurrent ()
	Draws the current state. More...

void	update ()
	Needs to be called with a valid GL context to finalize specific operations like volume loading.

void	setSize (int width, int height)
	Call this to change the viewport and projection matrices. More...

float	getFPS () const
	Returns the current FPS. More...

int	getLastSliceCount () const
	Gets the total number of slices that were processed in the last frame.

int	getLastRenderedSliceCount () const
	Gets the number of processed slices which were actually rendered. More...

bool	loadVolume (const QString &metadataFile, VolumeMetaData *loadedVolume=nullptr)
	The VolumeRenderer, with help of a VolumeLoader, loads the volume metadata and then the volume specified in the file given. More...

bool	loadVolume (VolumeMetaData &metadata)
	Loads the volume specified by the given metadata information, using the VolumeLoader. More...

VolumeMetaData	getCurrentVolume () const
	Returns the currently loaded volume meta data, contains garbage if nothing loaded yet.

Private Slots
void	processLogMessage (const QOpenGLDebugMessage &msg)
	Currently unused due to a bug in Qt 5.2 with AMD graphics cards.

Private Member Functions
bool	checkGLRequirements ()
	Tests if the current OpenGL context meets the requirements of the renderer. More...

QOpenGLShaderProgram *	createShader (const QString &vShaderName, const QString &fShaderName, const QString &gShaderName="")
	Helper function to create a OpenGL shader program, with vertex, fragment and optional geometry shader.

QOpenGLShaderProgram *	createComputeShader (const QString &cShaderName)
	Helper function to create a OpenGL compute shader program.

bool	initShaders ()
	Loads, compiles & links all shaders the renderer requires. More...

bool	initBuffers ()
	Initializes VAOs/VBOs etc, for bounding box, slices ... More...

bool	initTextures ()
	Initializes the required textures, currently rather empty because they are recreated in processVolume.

void	updateFBOs ()
	Creates/updates the required framebuffer objects to fit the current viewport size.

QVector< float >	setupGaussian (int &size)
	Calculates a 3D Gaussian convolution kernel depending on current sigma. More...

void	processVolume (const QByteArray &data)
	Processes the raw volume data passed according to the current metadata and settings. More...

void	updateProjection ()
	Calculates a new projection matrix depending on current viewport parameters.

void	traverseSlices (const QVector< QVector3D > &transformedBox, int count, float zStart, float zDelta)
	Traverses the transformed bounding box from the specified start point in the specified direction (delta).

int	traverseSlicesDOF (const QVector< QVector3D > &transformedBox, int count, float zStart, float zDelta, float focusZ, QOpenGLFramebufferObject **buffers)
	Like traverseSlices, but applies the DOF effects. More...

bool	updateSliceGeometry (const QVector< QVector3D > &box, const float zPos, GLint &firstIdx, GLsizei &count)
	Performs slicing of a view-aligned plane with the view-transformed volume bounding box, and uploads the slice to OpenGL, if it has intersections.

void	drawVolume ()

void	drawBoundingBox ()

void	drawLine (const QVector3D &pointA, const QVector3D &pointB, const QVector3D &color)

Private Attributes
class VolumeRendererPrivate &	d

QString	m_errString

Detailed Description

A state-based OpenGL renderer for simple volume rendering.

Nearly all functions assume a usable OpenGL context is available, the caller has to make sure that this is the case.

Constructor & Destructor Documentation

VolumeRenderer::VolumeRenderer ( QObject * parent = nullptr )

explicit

Sets up basic stuff.

initialize has to be called before the class is usable. The only method guaranteed to be usable before initialize is getDesiredFormat.

Member Function Documentation

bool VolumeRenderer::checkGLRequirements ( )

private

Tests if the current OpenGL context meets the requirements of the renderer.

The most "modern" feature required are compute shaders.

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void VolumeRenderer::drawCurrent ( )

Draws the current state.

The caller has to make sure all OpenGL stuff is valid (context, visible window etc.).

Note: The VolumeRenderWindow calls this in VoxelBlur.

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const QString VolumeRenderer::error ( ) const

inline

Returns the current error text of the renderer.

Currently only set when initialize fails.

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float VolumeRenderer::getFPS ( ) const

Returns the current FPS.

Only makes sense in animation mode. The value only uses the last frame, so it may be drastically inaccurate.

int VolumeRenderer::getLastRenderedSliceCount ( ) const

Gets the number of processed slices which were actually rendered.

This number is smaller than getLastSliceCount, and excludes slices with less than 3 intersections.

bool VolumeRenderer::initBuffers ( )

private

Initializes VAOs/VBOs etc, for bounding box, slices ...

*** BOX

*** LINE

*** SLICES

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bool VolumeRenderer::initialize ( )

Initializes the volume renderer, using the currently bound OpenGL context.

This loads all needed shaders, initializes buffers, FBOs etc. If this fails for some reason (unsupported GL version), false is returned and error returns an error text.

Note: The VolumeRenderWindow calls this in VoxelBlur.

Returns: true when all is correctly initialized.

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bool VolumeRenderer::initShaders ( )

private

Loads, compiles & links all shaders the renderer requires.

They are loaded through the Qt resource system.

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bool VolumeRenderer::loadVolume	(	const QString &	metadataFile,
		VolumeMetaData *	loadedVolume = `nullptr`
	)

The VolumeRenderer, with help of a VolumeLoader, loads the volume metadata and then the volume specified in the file given.

See Also: VolumeLoader

Parameters

metadataFile	a string identifying the metadata file that includes volume information
loadedVolume	if the volume loaded successfully, returns the metadata of the volume

Returns: true if loading ok, false if not

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bool VolumeRenderer::loadVolume ( VolumeMetaData & metadata )

Loads the volume specified by the given metadata information, using the VolumeLoader.

Parameters

metadata The metadata which identify a volume file to load

Returns: true of loading ok

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void VolumeRenderer::processVolume ( const QByteArray & data )

private

Processes the raw volume data passed according to the current metadata and settings.

This includes Gaussian filtering, Gradient calculation, data scaling and flipping.

Parameters

data	the raw volume data

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void VolumeRenderer::requestDraw ( )

signal

Emitted when the state of the renderer is changed in a way that would change the rendered image.

Because the VolumeRenderer can not start rendering itself (it has no way to be sure the context is bound, that the window is visible etc), it instead notifies interested object that a change has occurred.

Things that cause the signal to be emitted include changes in camera parameters (like setRotation or setDistance). If another signal is associated with this changes (like distanceChanged), it will always be emitted before requestDraw is emitted.

Note: The VolumeRenderWindow handles this in VoxelBlur.

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void VolumeRenderer::setBlurAmount ( float R )

slot

Sets the rate at which the blurring increases with distance to the focal plane.

Should be larger than zero.

void VolumeRenderer::setFocalPlane ( float d )

slot

Sets the distance to the focal plane, \( d \in [0,1]\).

0 corresponds to the Z value nearest to the camera, 1 to the one farthest away

void VolumeRenderer::setLightParameters	(	float	azimuth,
		float	angle
	)

slot

Sets the light parameters.

The light source is directional, identified by azimuth angle around the Y vector and elevation angle around the local Z. When both are 0, this corresponds to a light vector of \( (1,0,0) \).

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void VolumeRenderer::setSize	(	int	width,
		int	height
	)

Call this to change the viewport and projection matrices.

Note: This does NOT emit the requestDraw signal.

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QVector< float > VolumeRenderer::setupGaussian ( int & size )

private

Calculates a 3D Gaussian convolution kernel depending on current sigma.

The kernel has equal size in all dimensions.

Parameters

size	an output parameter, containing the size of the kernel in each dimension.

Returns: a 3D Gaussian convolution kernel in linear form

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int VolumeRenderer::traverseSlicesDOF	(	const QVector< QVector3D > &	transformedBox,
		int	count,
		float	zStart,
		float	zDelta,
		float	focusZ,
		QOpenGLFramebufferObject **	buffers
	)

private

Like traverseSlices, but applies the DOF effects.

The returned int is the index of the last draw buffer which should be merged with the other direction result.

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The documentation for this class was generated from the following files:

Public Types

Public Slots

Signals

Public Member Functions

Private Slots

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation