Transform data before texture creation. More...

#include <VolumeViz/nodes/SoVolumeTransform.h>

Inheritance diagram for SoVolumeTransform:

Public Member Functions
virtual SoType	getTypeId () const
	Returns the type identifier for this specific instance.

	SoVolumeTransform ()
	Constructor.

virtual void	apply (SoState state, const SoLDM::DataSetIdPair &p, SoBufferObject bufferObject, const SoLDMTileID &id)=0
	Apply in-place transformation to the specified dataset tile.

virtual SbBool	isValid (SoState state, const SoLDM::DataSetIdPair &p, SoBufferObject bufferObject, const SoLDMTileID &id)
	Should return TRUE if the given parameters are valid for this compute function.

virtual void	getTransformedMinMax (double &min, double &max)
	Based on min max of the input data, this function should return the expected data range of the result (transformed) data.

SoBufferObject *	getFromCache (const SoLDMTileID &tileID)
	Returns the previously transformed data for a specific tile.

void	addInCache (const SoLDMTileID &tileID, SoBufferObject *bufferObject)
	Add the transformed data for a specific tile to the cache.

Public Member Functions inherited from SoNode
virtual void	setOverride (const SbBool state)
	Turns the override flag on or off.

virtual SbBool	isOverride () const
	Returns the state of the override flag.

virtual SoNode *	copy (SbBool copyConnections=FALSE) const
	Creates and returns an exact copy of the node.

virtual SbBool	affectsState () const
	Returns TRUE if a node has an effect on the state during traversal.

virtual void	touch ()
	Marks an instance as modified, simulating a change to it.

Public Member Functions inherited from SoFieldContainer
void	setToDefaults ()
	Sets all fields in this object to their default values.

SbBool	hasDefaultValues () const
	Returns TRUE if all of the object's fields have their default values.

SbBool	fieldsAreEqual (const SoFieldContainer *fc) const
	Returns TRUE if this object's fields are exactly equal to fc's fields.

void	copyFieldValues (const SoFieldContainer *fc, SbBool copyConnections=FALSE)
	Copies the contents of fc's fields into this object's fields.

SoNONUNICODE SbBool	set (const char *fieldDataString)
	Sets one or more fields in this object to the values specified in the given string, which should be a string in the Open Inventor file format.

SbBool	set (const SbString &fieldDataString)
	Sets one or more fields in this object to the values specified in the given string, which should be a string in the Open Inventor file format.

void	get (SbString &fieldDataString)
	Returns the values of the fields of this object in the Open Inventor ASCII file format in the given string.

virtual int	getFields (SoFieldList &list) const
	Appends references to all of this object's fields to resultList, and returns the number of fields appended.

virtual int	getAllFields (SoFieldList &list) const
	Returns a list of fields, including the eventIn's and eventOut's.

virtual SoField *	getField (const SbName &fieldName) const
	Returns a the field of this object whose name is fieldName.

virtual SoField *	getEventIn (const SbName &fieldName) const
	Returns a the eventIn with the given name.

virtual SoField *	getEventOut (const SbName &fieldName) const
	Returns the eventOut with the given name.

SbBool	getFieldName (const SoField *field, SbName &fieldName) const
	Returns the name of the given field in the fieldName argument.

SbBool	enableNotify (SbBool flag)
	Notification at this Field Container is enabled (if flag == TRUE) or disabled (if flag == FALSE).

SbBool	isNotifyEnabled () const
	Notification is the process of telling interested objects that this object has changed.

virtual void	setUserData (void *data)
	Sets application data.

void *	getUserData (void) const
	Gets user application data.

Public Member Functions inherited from SoBase
virtual SbName	getName () const
	Returns the name of an instance.

virtual void	setName (const SbName &name)
	Sets the name of an instance.

void	setSynchronizable (const bool b)
	Sets this to be a ScaleViz synchronizable object.

bool	isSynchronizable () const
	Gets the ScaleViz synchronizable state of this object.

Public Member Functions inherited from SoRefCounter
void	ref () const
	Adds a reference to an instance.

void	unref () const
	Removes a reference from an instance.

void	unrefNoDelete () const
	unrefNoDelete() should be called when it is desired to decrement the reference count, but not delete the instance if this brings the reference count to zero.

int	getRefCount () const
	Returns current reference count.

void	lock () const
	lock this instance.

void	unlock () const
	unlock this instance.

Public Member Functions inherited from SoTypedObject
SbBool	isOfType (const SoType &type) const
	Returns TRUE if this object is of the type specified in type or is derived from that type.

template<typename TypedObjectClass >
SbBool	isOfType () const
	Returns TRUE if this object is of the type of class TypedObjectClass or is derived from that class.

Static Public Member Functions
static SoType	getClassTypeId ()
	Returns the type identifier for this class.

Static Public Member Functions inherited from SoNode
static SoType	getClassTypeId ()
	Returns the type identifier for this class.

static SoNode *	getByName (const SbName &name)
	A node's name can be set using SoBase::setName().

static int	getByName (const SbName &name, SoNodeList &list)
	A node's name can be set using SoBase::setName().

Static Public Member Functions inherited from SoFieldContainer
static SoType	getClassTypeId ()
	Returns the type of this class.

Static Public Member Functions inherited from SoBase
static SoType	getClassTypeId ()
	Returns type identifier for this class.

Static Public Member Functions inherited from SoTypedObject
static SoType	getClassTypeId ()
	Returns the type identifier for this class.

Public Attributes
SoSFShort	volumeTransformId
	Allows the transform to be applied to all or one specific data set.

SoSFInt32	cacheSize
	Size of the computed tile cache for this transform.

Detailed Description

Transform data before texture creation.

The SoVolumeTransform node allows an application to apply a defined computation on LDM data tiles just before they are sent to the GPU. There are several other ways to apply a computation to LDM tiles, that are applied at different stages of the pipeline. The SoLDMDataTransform class for example (see the dataTransform field of SoDataSet) applies a computation to each LDM tile requested from the volume reader before the tile is stored in system memory. This can be used to create multiple data sets from a single input (e.g. on disk) data set, but has the drawback that each resulting data set must be stored in system memory. SoVolumeTransform can be used to create multiple data sets from a single data set in system memory and does not require storing the created data sets in system memory (only on the GPU).

A cache mechanism, local to each instance of SoVolumeTransform, allows storing the computed tiles for later reuse. The size of this cache (number of tiles to cache) can be specified using the cacheSize field. We recommend setting the cacheSize to the number of tiles needed to display the biggest expected slice. As an example, for a dataset of size 128x512x1024 with a tile size equal to 128, the biggest slice size is 512x1024. So 4x8 = 32 LDM tiles are needed for rendering and therefore a cacheSize of 32 (tiles) is needed to avoid computing the same tile multiple times. The apply method can retrieve the transformed data for other tiles from the cache and can explicitly add the transformed data for other tiles to the cache.

SoVolumeTransform works on tiles (not slices or volumes). If a compute function needs data from other tiles, the application may use the SoLDMDataAccess API to get that data. (This is another difference from SoLDMDataTransform, which does not allow using the LDM data access API.)

Multiple SoVolumeTransform nodes may be applied to the same SoDataSet. The transforms are applied in the order of their appearance in the scene graph. SoVolumeTransform nodes may also be applied only to a specific SoDataSet using the volumeTransformId field. If this field is zero (the default), the transform is applied to all subsequent data set nodes. Else the transform is only applied to data sets whose dataSetId field contains the same value as the volumeTransformId.

SoVolumeTransform is based on the Open Inventor computing framework and uses the SoBufferObject classes to abstract and manage blocks of memory. The application can use different devices to implement the computation, and manage input tiles and output tiles stored on different devices.

As mentioned previously, SoVolumeTransform can be used to create multiple data sets on-the-fly from a single data set in system memory. In this case the same data set node will be instanced multiple times in the scene graph (although its data will only be loaded in system memory once), but we still need to assign each data texture a unique id so the shader program can access them uniquely. This is done using SoDataSetId nodes to specify a different data set id for each instance of the data set node. If an SoDataSetId node is in the traversal state when a data set node is traversed, the dataSetId field is ignored and the id from the SoDataSetId node is used.

To implement a computation, the application must derive a new class from SoVolumeTransform and (at least) implement the apply() method, which performs the actual computation. This method is called with parameters that give access to information about the data set and the specific tile being computed. In a simple case you might only need to access the buffer object.

It may also be useful to implement the isValid() and getTransformedMinMax() methods. The isValid() method will be called for each tile immediately before the apply() method. If this method returns FALSE, then the apply() method will not be called for that tile. If the application can compute or estimate the min and max values of the computed data set, then it should implement the getTransformedMinMax() method so VolumeViz does not do unnecessary work to compute these values.

FILE FORMAT/DEFAULT

volumeTransformId	0
cacheSize	1

ACTION BEHAVIOR

SoCallbackAction

SoGLRenderAction

Constructor & Destructor Documentation

◆ SoVolumeTransform()

SoVolumeTransform::SoVolumeTransform ( )

Constructor.

Member Function Documentation

◆ addInCache()

void SoVolumeTransform::addInCache	(	const SoLDMTileID &	tileID,
		SoBufferObject *	bufferObject
	)

Add the transformed data for a specific tile to the cache.

It is not necessary to call this method for the current tile, it will be added to the cache automatically. This method is useful if the apply method computes transformed data for other tiles. These tiles can be saved in the cache to avoid recomputing them later.

◆ apply()

virtual void SoVolumeTransform::apply	(	SoState *	state,
		const SoLDM::DataSetIdPair &	p,
		SoBufferObject *	bufferObject,
		const SoLDMTileID &	id
	)

pure virtual

Apply in-place transformation to the specified dataset tile.

The application must implement this method in the derived class.

Parameters

state	Current traversal state.
p	Dataset/id pair (p.first is an SoDataSet, p.second is a dataSetId) Using the SoDataSet object you can obtain, for example, the actual data type of the data: SoDataSet pDataSet = p.first; SoDataSet::dataType type = pDataSet->getDataType(); SoDataSet <a href="IconLegend.html"><img src="extLDM.gif" alt="Large Data Management" border="0"></a> Data set... Definition SoDataSet.h:139 SoDataSet::getDataType DataType getDataType() Returns the data type.
bufferObject	The buffer that contains the data
id	Tile to be transformed Using this id and the SoDataSet object you can obtain, for example, the actual position of the tile in the volume: SbBox3i32 tilePos = pDataSet->getNodeFrontManager()->getTilePos( id ); SbBox3i32 <a href="IconLegend.html"><img src="extTGS.gif" alt="VSG extension" border="0"></a> 3D box class. Definition SbBox.h:96

◆ getClassTypeId()

static SoType SoVolumeTransform::getClassTypeId ( )

static

Returns the type identifier for this class.

◆ getFromCache()

SoBufferObject * SoVolumeTransform::getFromCache ( const SoLDMTileID & tileID )

Returns the previously transformed data for a specific tile.

This method is useful if the apply method depends on transformed data for other tiles, for example adjacent tiles. If the needed tiles have already been transformed and saved in the cache, then it is not necessary to recompute them. Returns NULL if the tile was not found in the cache. See also the cacheSize field.

◆ getTransformedMinMax()

void SoVolumeTransform::getTransformedMinMax	(	double &	min,
		double &	max
	)

inlinevirtual

Based on min max of the input data, this function should return the expected data range of the result (transformed) data.

Definition at line 305 of file SoVolumeTransform.h.

◆ getTypeId()

virtual SoType SoVolumeTransform::getTypeId ( ) const

virtual

Returns the type identifier for this specific instance.

Reimplemented from SoNode.

◆ isValid()

virtual SbBool SoVolumeTransform::isValid	(	SoState *	state,
		const SoLDM::DataSetIdPair &	p,
		SoBufferObject *	bufferObject,
		const SoLDMTileID &	id
	)

virtual

Should return TRUE if the given parameters are valid for this compute function.

If not the apply function will not be called for this tile. The interpretation of "valid" is up to the application. For example, you could use this function to skip computing for low resolution tiles.

Parameters

state	Current traversal state.
p	Dataset/id pair (p.first is an SoDataSet*, p.second is a dataSetId)
bufferObject	The buffer that contains the data
id	Tile to be transformed

Member Data Documentation

◆ cacheSize

SoSFInt32 SoVolumeTransform::cacheSize

Size of the computed tile cache for this transform.

This is the number of computed tiles that will be cached and will not need to be recomputed. Choose a value to balance between memory usage and computing time. Default is 1.

Definition at line 155 of file SoVolumeTransform.h.

◆ volumeTransformId

SoSFShort SoVolumeTransform::volumeTransformId

Allows the transform to be applied to all or one specific data set.

A volume transform id of 0 means that this transform will be applied to all subsequent data sets. A value greater than 0 means that this transform will only be applied to data sets with a matching data set id. For example, if the transform id is 1, the transform will only be applied to data sets whose data set id is also 1. The default value is 0.

Definition at line 147 of file SoVolumeTransform.h.

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

VolumeViz/nodes/SoVolumeTransform.h

Open Inventor Release 2023.2.3

Public Member Functions

Static Public Member Functions

Public Attributes