Renders digital radiograph reconstructs of volume geometries in the scene. More...

#include <DRRStage.h>

Inheritance diagram for Carna::presets::DRRStage:

Collaboration diagram for Carna::presets::DRRStage:

Public Member Functions
	DRRStage (unsigned int geometryType)
	Instantiates. The created stage will render such base::Geometry scene graph nodes, whose geometry types equal geometryType.

virtual	~DRRStage ()
	Deletes.

DRRStage *	clone () const override
	Returns same `RenderStage` implementation with same configuration. More...

virtual void	reshape (base::FrameRenderer &fr, unsigned int width, unsigned int height) override
	Orders this stage to reshape its buffers according to the specified dimensions. More...

virtual void	renderPass (const base::math::Matrix4f &viewTransform, base::RenderTask &rt, const base::Viewport &vp) override
	Computes the digital radiograph reconstruct like described here.

float	waterAttenuation () const
	Tells \(\mu_\text{water}\). The parameters are described here.

float	baseIntensity () const
	Tells \(I_0\). The parameters are described here.

base::HUV	lowerThreshold () const
	Tells \(\mathrm{hu}_\text{lower}\). The parameters are described here.

base::HUV	upperThreshold () const
	Tells \(\mathrm{hu}_\text{upper}\). The parameters are described here.

float	upperMultiplier () const
	Tells \(\lambda\). The parameters are described here.

bool	isRenderingInverse () const
	Tells whether ray attenuation at any particular pixel is inverse proportional to the brightness of that pixel or just proportional.

void	setWaterAttenuation (float muWater)
	Sets \(\mu_\text{water}\) to muWater. The parameters are described here.

void	setBaseIntensity (float baseIntensity)
	Sets \(I_0\) to baseIntensity. The parameters are described here.

void	setLowerThreshold (base::HUV lower)
	Sets \(\mathrm{hu}_\text{lower}\) to lower. The parameters are described here.

void	setUpperThreshold (base::HUV upper)
	Sets \(\mathrm{hu}_\text{upper}\) to upper. The parameters are described here.

void	setUpperMultiplier (float multiplier)
	Sets \(\lambda\) to multiplier. The parameters are described here.

void	setRenderingInverse (bool inverse)
	Sets whether the colors of the DRR should be inverse or not. The ray attenuation at a particular pixel is proportional to the brightness of that pixel if inverse is `false`. More...

Public Member Functions inherited from Carna::presets::VolumeRenderingStage
	VolumeRenderingStage (unsigned int geometryType)
	Instantiates. The created stage will render such base::Geometry scene graph nodes, whose geometry types equal geometryType.

virtual	~VolumeRenderingStage ()
	Deletes.

void	setSampleRate (unsigned int sampleRate)
	Sets number of slices to be rendered per segment. More...

unsigned int	sampleRate () const
	Tells number of slices to be rendered per segment. More...

Public Member Functions inherited from Carna::base::GeometryStage< base::Renderable::BackToFront >
	GeometryStage (unsigned int geometryType, unsigned int geometryTypeMask=RenderQueue< base::Renderable::BackToFront >::EXACT_MATCH_GEOMETRY_TYPE_MASK)
	Instantiates s.t. the predefined rendering queue enqueues such Carna::base::Geometry scene graph nodes, whose geometry type AND-linked with geometryTypeMask equals the geometryType specified here.

virtual	~GeometryStage ()
	Releases acquired video resources.

virtual void	prepareFrame (Node &root) override
	Called once before each frame. More...

std::size_t	renderedPassesCount () const
	Tells the number of passes rendered so far since the beginning of the current frame.

GeometryFeatureType::ManagedInterface &	videoResource (GeometryFeatureType &geometryFeature) const
	Interfaces the geometryFeature video resources that were acquired by this rendering stage.

const GeometryFeatureType::ManagedInterface &	videoResource (const GeometryFeatureType &geometryFeature) const

Public Member Functions inherited from Carna::base::RenderStage
	RenderStage ()
	Instantiates in enabled-state.

virtual	~RenderStage ()
	Deletes.

void	setViewTransformFixed (bool viewTransformFixed)
	Sets whether the view transform is pass-invariant for the duration of a single frame. More...

bool	isViewTransformFixed () const
	Tells whether the view transform is pass-invariant for the duration of a single frame.

bool	isInitialized () const
	Tells whether this stage is ready for rendering. More...

bool	isEnabled () const
	Tells whether this stage is enabled. Disabled stages are not rendered by render tasks.

void	setEnabled (bool)
	Sets whether this stage is enabled. Disabled stages are not rendered by render tasks.

base::FrameRenderer &	renderer ()
	References the renderer this stage belongs to. More...

const base::FrameRenderer &	renderer () const

void	addRenderStageListener (RenderStageListener &listener)
	Adds listener to the set of listeners this instance notifies in \(\mathcal O\left(\log n\right)\).

void	removeRenderStageListener (RenderStageListener &listener)
	Removes listener from the set of listeners this instance notifies in \(\mathcal O\left(\log n\right)\).

Static Public Attributes
static const float	DEFAULT_WATER_ATTENUATION
	Holds default value for \(\mu_\text{water}\).

static const float	DEFAULT_BASE_INTENSITY
	Holds default value for \(I_0\).

static const base::HUV	DEFAULT_LOWER_THRESHOLD
	Holds default value for \(\mathrm{hu}_\text{lower}\).

static const base::HUV	DEFAULT_UPPER_THRESHOLD
	Holds default value for \(\mathrm{hu}_\text{upper}\).

static const float	DEFAULT_UPPER_MULTIPLIER
	Holds default value for \(\lambda\).

static const bool	DEFAULT_RENDER_INVERSE
	Holds default value for inverse rendering.

static const unsigned int	ROLE_INTENSITIES = 0
	Holds the role that HU volume data is expected to take when attached to base::Geometry nodes.

Static Public Attributes inherited from Carna::presets::VolumeRenderingStage
static const unsigned int	DEFAULT_SAMPLE_RATE = 200
	Holds the default number of slices rendered per segment.

Protected Member Functions
virtual unsigned int	loadVideoResources () override
	Loads video resources when rendering is triggered for the first time. Override this method if you need any additional resources to be loaded, but always call the base implementation. More...

virtual void	createVolumeSamplers (const std::function< void(unsigned int, base::Sampler *) > &registerSampler) override
	Creates texture samplers for volume textures and uses registerSampler to assign them to the roles that they should be used with.

virtual const base::ShaderProgram &	acquireShader () override
	Acquires the `drr_accumulation` shader from the base::ShaderManager.

virtual const std::string &	uniformName (unsigned int role) const override
	Maps ROLE_INTENSITIES to `huVolume`.

virtual void	configureShader () override
	Uploads the parameters to the shader.

virtual void	configureShader (const base::Renderable &) override
	Does nothing.

Protected Member Functions inherited from Carna::presets::VolumeRenderingStage
virtual void	render (const base::Renderable &) override
	Renders the renderable.

Protected Member Functions inherited from Carna::base::GeometryStage< base::Renderable::BackToFront >
void	activateGLContext () const
	Ensures that the OpenGL context of the hosting Carna::base::FrameRenderer is the current one.

virtual void	buildRenderQueues (Node &root, const math::Matrix4f &viewTransform)
	Builds the rendering queues of this stage.

virtual void	rewindRenderQueues ()
	Rewinds the rendering queues of this stage.

virtual void	updateRenderQueues (const math::Matrix4f &viewTransform)
	Recomputes the model-view transforms of the renderables enqueued by this stage.

Additional Inherited Members
Public Attributes inherited from Carna::base::GeometryStage< base::Renderable::BackToFront >
const unsigned int	geometryType
	Renders such geometries whose type AND-linked with geometryTypeMask equals this.

const unsigned int	geometryTypeMask
	Renders such geometries whose type AND-linked with this equals geometryType.

Protected Attributes inherited from Carna::base::GeometryStage< base::Renderable::BackToFront >
RenderQueue< base::Renderable::BackToFront >	rq
	Holds the predefined rendering queue of this rendering stage.

Detailed Description

Renders digital radiograph reconstructs of volume geometries in the scene.

Background

For each pixel of the output framebuffer, a ray is casted into the scene. This ray occasionally intersects volumetric data, that is assigned to geometry nodes. This ray defines a one-dimensional space. We denote its coordinates with \(x\). Further, we write \(\mathrm{hu}\left(x\right)\) to denote the HU value at location \(x\).

This rendering stage computes

\[ I = I_o \exp\left( -\int_{-\infty}^{\infty} g\left(x\right) \mu\left(x\right) \,\mathrm dx \right) \]

with

\[ \mu\left(x\right) = \mu_\text{water} \cdot \left(1+\frac{\mathrm{hu}\left(x\right)}{1000}\right)\text. \]

The function \(g\left(x\right)\) yields some non-linearity, where \(\lambda\) is an arbitrary positive factor:

\[ g\left(x\right) = \begin{cases} 0 & \text{if} & \mathrm{hu}_\text{lower} > \mathrm{hu}\left(x\right) \\ 1 & \text{if} & \mathrm{hu}_\text{lower} \geq \mathrm{hu}\left(x\right) < \mathrm{hu}_\text{upper} \\ \lambda & \text{if} & \mathrm{hu}_\text{upper} \leq \mathrm{hu}\left(x\right) \end{cases} \]

The integral \(y = \int_{-\infty}^{\infty} g\left(x\right) \mu\left(x\right) \,\mathrm dx\) is computed through VolumeRenderingStage::renderPass. For each pixel, the result is written to a texture. Afterwards this texture is drawn back to the output buffer, using a shader the computes \(I = I_0 \exp\left(-y\right)\). The resulting colors are defined as \(I \mapsto \left(1, 1, 1, 1 - I\right)^\mathrm T\) if inverse rendering is disabled, or \(I \mapsto \left(0, 0, 0, 1 - I\right)^\mathrm T\) otherwise. The fourth component of the color vector is the opacity.

Usage

The DRRStage constructor takes a geometry type parameter:

drr = new presets::DRRStage( GEOMETRY_TYPE_VOLUMETRIC );

renderer->appendStage( drr );

The concept of geometry types is explained here.

Note: In the rendering process this stage will usually be inserted after such stages that render opaque geometry, like CuttingPlanesStage and OpaqueRenderingStage.

The following example code configures the DRRStage s.t. it produces the rendering presented further below:

    drr->setSampleRate( 100 );
    drr->setWaterAttenuation( 5e-3f );
    drr->setBaseIntensity( 1.f );
    drr->setLowerThreshold( base::HUV::abs( -400 ) );
    drr->setUpperThreshold( base::HUV::abs( +400 ) );
    drr->setUpperMultiplier( 1.5f );

The last step is to state that the brightness of any particular pixel shall be inverse proportional to the ray attenuation at that pixel:

drr->setRenderingInverse( true );

renderer->setBackgroundColor( base::Color::WHITE_NO_ALPHA );

exemplary rendering in inverse-mode from code above

Author: Leonid Kostrykin

Date: 22.2.15 - 11.3.15

Definition at line 106 of file DRRStage.h.

Member Function Documentation

◆ clone()

DRRStage* Carna::presets::DRRStage::clone ( ) const

overridevirtual

Returns same RenderStage implementation with same configuration.

The listeners and the rendering state are not copied.

Deprecated:: Do not use this method. It will be removed shortly.

Implements Carna::base::RenderStage.

◆ loadVideoResources()

virtual unsigned int Carna::presets::DRRStage::loadVideoResources ( )

overrideprotectedvirtual

Loads video resources when rendering is triggered for the first time. Override this method if you need any additional resources to be loaded, but always call the base implementation.

Returns: the first texture unit to use for volume textures. The dafault implementation returns base::Texture<0>::SETUP_UNIT +1.

Reimplemented from Carna::presets::VolumeRenderingStage.

◆ reshape()

virtual void Carna::presets::DRRStage::reshape	(	base::FrameRenderer &	fr,
		unsigned int	width,
		unsigned int	height
	)

overridevirtual

Orders this stage to reshape its buffers according to the specified dimensions.

Attention: Always call the base implementaion!

Parameters

fr	references the frame renderer this stage belongs to.
width	is the root viewport width.
height	is the root viewport height.

Reimplemented from Carna::base::RenderStage.

◆ setRenderingInverse()

void Carna::presets::DRRStage::setRenderingInverse ( bool inverse )

Sets whether the colors of the DRR should be inverse or not. The ray attenuation at a particular pixel is proportional to the brightness of that pixel if inverse is false.

If you set inverse to true, you will also have to change the rendering's background color from default black to something brighter, like white. Otherwise you might not see any rendering results from this stage. Default value is false.

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

include/Carna/presets/DRRStage.h

Public Member Functions

Static Public Attributes

Protected Member Functions

Additional Inherited Members