Performs direct volume renderings of the volume geometries in the scene. More...

#include <DVRStage.h>

Inheritance diagram for Carna::presets::DVRStage:

Collaboration diagram for Carna::presets::DVRStage:

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

virtual	~DVRStage ()
	Deletes.

DVRStage *	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
	Triggers the volume rendering.

void	clearColorMap ()
	Clears the color map. All HU values are mapped to base::Color::BLACK_NO_ALPHA after calling this method.

void	writeColorMap (const base::math::Span< base::HUV > &huRange, const base::math::Span< base::Color > colorRange)
	Maps all HU values from huRange to colorRange. The first/last HU value from huRange is mapped to the first/last value of colorRange, respectively. The values are interpolated linearly in between. More...

void	writeColorMap (base::HUV huFirst, base::HUV huLast, const base::Color &colorFirst, const base::Color &colorLast)

void	setTranslucence (float translucence)
	Sets the translucence property.

float	translucence () const
	Tells current translucence.

void	setDiffuseLight (float diffuseLight)
	Sets the diffuse light amount to diffuseLight and the ambient light amount to one minus diffuseLight. More...

float	diffuseLight () const
	Tells the diffuse light amount. The ambient light amount is one minus the diffuse light amount.

bool	isLightingUsed () const
	Tells whether lighting was used during the last rendering. The return value is undefined if nothing was rendered yet.

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

static const unsigned int	ROLE_NORMALS = 1
	Holds the role that the normal map is expected to take when attached to base::Geometry nodes.

static const float	DEFAULT_TRANSLUCENCE
	Holds the default translucence.

static const float	DEFAULT_DIFFUSE_LIGHT
	Holds the default diffuse light amount. The ambient light amount is always one minus the diffuse light amount.

Static Public Attributes inherited from Carna::presets::VolumeRenderingStage
static const unsigned int	DEFAULT_SAMPLE_RATE = 100
	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 `dvr` shader from the base::ShaderManager.

virtual const std::string &	uniformName (unsigned int role) const override
	Maps ROLE_HU_VOLUME to `huVolume` and ROLE_NORMALS to `normalMap`.

virtual void	configureShader () override
	Performs custom shader configuration on a per-pass level.

virtual void	configureShader (const base::Renderable &) override
	Computes and uploads the normals transformation matrix.

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

Performs direct volume renderings of the volume geometries in the scene.

Usage

The DVRStage constructor takes a geometry type parameter:

dvr = new presets::DVRStage( GEOMETRY_TYPE_VOLUMETRIC );

renderer->appendStage( dvr );

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 DVRStage supports two types of rendering modes: Rendering with lighting enabled and rendering without lighting. In general, lighting produces more sculptural results, but it comes at the cost of additional requirements: Not only the HU volume must be uploaded to the GPU, but also another 3D texture that maps texture space coordinates to the normal vectors of the surface at a particular location. Depending on the resolution of the data, this might cause noteworthy memory consumption.

Luckily the helpers::VolumeGridHelper class does everything that is needed in order to compute the normal vectors and upload them to the GPU, if it is instructed to do so: Its second type argument is optional and set to void by default. This disables its normal vectors support. Setting it to anything different, like base::NormalMap3DInt8 for example, makes it compute the normal vectors when helpers::VolumeGridHelper::loadData or its computeNormals method are called.

The DVRStage decides which mode to use depending on whether the normal vectors are provided or not.

Without Lighting

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

dvr->writeColorMap( -400, 0, base::Color:: BLUE_NO_ALPHA, base::Color:: BLUE );

dvr->writeColorMap( 0, 400, base::Color::GREEN_NO_ALPHA, base::Color::GREEN );

This gives the following rendering:

exemplary rendering without lighting from code above

Translucence

The translucence scales the opacity values queried from the color map. Assuming that \(\alpha\) was the value from the color map, the translucence \(t \geq 0\) scales the actual opacity to \(\frac{\alpha}{1 + t}\).

With Lighting Enabled

The default translucence is quite high, which is fine for rendering without lighting. You might consider setting it down when rendering with lighting enabled:

    dvr->writeColorMap( -400,   0, base::Color:: BLUE_NO_ALPHA, base::Color:: BLUE );
    dvr->writeColorMap(    0, 400, base::Color::GREEN_NO_ALPHA, base::Color::GREEN );
    dvr->setSampleRate( 500 );
    dvr->setTranslucence( 2 );

This gives the following rendering:

exemplary rendering with lighting from code above

Author: Leonid Kostrykin

Date: 25.3.15 - 29.3.15

Definition at line 101 of file DVRStage.h.

Member Function Documentation

DVRStage* Carna::presets::DVRStage::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.

virtual unsigned int Carna::presets::DVRStage::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.

virtual void Carna::presets::DVRStage::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.

void Carna::presets::DVRStage::setDiffuseLight ( float diffuseLight )

Sets the diffuse light amount to diffuseLight and the ambient light amount to one minus diffuseLight.

Precondition: diffuseLight >= 0 && diffuseLight <= 1

This only has an effect if lighting is enabled. If lighting is enabled, setting this to \(0\) virtually disables the lighting.

void Carna::presets::DVRStage::writeColorMap	(	const base::math::Span< base::HUV > &	huRange,
		const base::math::Span< base::Color >	colorRange
	)

Maps all HU values from huRange to colorRange. The first/last HU value from huRange is mapped to the first/last value of colorRange, respectively. The values are interpolated linearly in between.

Nothing happens if the last HU value of huRange is smaller than the first. If the first and the last HU values of huRange are equal, they are mapped to the mean of the first and the last values from colorRange.

void Carna::presets::DVRStage::writeColorMap	(	base::HUV	huFirst,
		base::HUV	huLast,
		const base::Color &	colorFirst,
		const base::Color &	colorLast
	)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

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

include/Carna/presets/DVRStage.h

Public Member Functions

Static Public Attributes