SoObliqueSlice Class Reference

Oblique slice shape node. More...

#include <VolumeViz/nodes/SoObliqueSlice.h>

Inheritance diagram for SoObliqueSlice:

Public Member Functions
virtual SoType	getTypeId () const
	Returns the type identifier for this specific instance.
	SoObliqueSlice ()
	Constructor.
Public Member Functions inherited from SoVolumeShape
virtual void	setRenderProgress (SoProgressIndicator *ps)
	Set an application defined SoProgressIndicator object which will raise an event before and after the rendering task, before and after each subtask (in this case: Texture creation and Geometry creation) and after each step in the subtasks which represents in most cases individual tiles of data.
Public Member Functions inherited from SoShape
virtual SbBool	affectsState () const
	Overrides default method on SoNode.
ShapeType	getShapeType ()
	Gets the current shape Full Scene Antialiasing type.
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 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 SoSlice
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
Static Public Member Functions inherited from SoVolumeShape
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
Static Public Member Functions inherited from SoLdmShape
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
Static Public Member Functions inherited from SoShape
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
static SbBool	isPrimitiveRestartAvailable (SoState *state=NULL)
	Returns TRUE if the primitive restart feature is available.
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
SoSFInt32	dataSetId
	Specifies the SoVolumeData node to use.
SoSFPlane	plane
	Plane defining the slice.
Public Attributes inherited from SoSlice
SoSFBool	enableBumpMapping
	Specifies if a bump mapping effect will be applied to the slice.
SoSFFloat	bumpScale
	Specifies the intensity of the bump mapping effect.
SoSFNode	alternateRep
	This field optionally holds a subgraph containing only core Open Inventor nodes that can be used for rendering when VolumeViz is not available.
SoSFEnum	alphaUse
	Specifies how to use the alpha component of each voxel's RGBA value.
SoSFBool	useRGBA
	Specifies whether to create RGBA textures.
SoSFBool	largeSliceSupport
	Activate/deactivate direct loading of full resolution slice data.
Public Attributes inherited from SoVolumeShape
SoSFEnum	interpolation
	Interpolation mode.
SoDEPRECATED SoSFEnum	composition
	Specifies color composition mode.
Public Attributes inherited from SoShape
SoSFBool	boundingBoxIgnoring
	Whether to ignore this node during bounding box traversal.

Friends
class	SoObliqueSliceLdm

Additional Inherited Members
Public Types inherited from SoSlice
enum	AlphaUse {   ALPHA_AS_IS ,   ALPHA_OPAQUE ,   ALPHA_BINARY }
	Alpha component usage mode Used in the alphaUse field. More...
Public Types inherited from SoVolumeShape
enum	Interpolation {   NEAREST ,   LINEAR ,   TRILINEAR ,   MULTISAMPLE_12 ,   CUBIC }
	Interpolation mode. More...
enum	Composition {   MAX_INTENSITY = 0 ,   MIN_INTENSITY ,   SUM_INTENSITY ,   ALPHA_BLENDING ,   COMPOSITION_LAST }
	Composition mode. More...
Public Types inherited from SoShape
enum	ShapeType {   POINTS ,   LINES ,   POLYGONS ,   TEXT }
	Basic type for antialiased rendering for this shape (Do not consider the SoDrawStyle property currently in the state). More...

Detailed Description

Oblique slice shape node.

This node defines an oblique (arbitrarily oriented) slice which is the intersection of the volume data defined by an SoVolumeData node and the plane defined by the plane field.

The SoVolumeData node can be specified with dataSetId. When this field is set to 0, the last SoVolumeData node on state is used.

For a non-RGBA (scalar valued) volume, each voxel's RGBA value is determined by the current SoDataRange and SoTransferFunction. The current diffuse color and transparency (set, for example, with an SoMaterial node) modify the appearance of the slice. This means that, for example, the current transparency can be used as a global alpha value to modulate the overall opacity of the slice.
For an RGBA volume each voxel's RGBA value comes directly from the volume data.

The interpolation field controls how the texture is interpolated.

The alphaUse field (SoSlice) controls how the voxel's alpha component is used when drawing the slice.

Optionally a bump mapping effect may be applied. Normal vectors are automatically computed from the data value gradient. The enableBumpMapping and bumpScale fields (SoSlice) control whether bump mapping is active and the intensity of the effect.

Notes:

• Transformation matrices:
  The volume size and orientation (like geometry) can be modified by transformation nodes in the scene graph and this in turn modifies the appearance of volume visualization nodes. However the same transformation must be applied to the volume data node and all volume visualization nodes associated with that volume. So effectively any transformation nodes that affect the volume must be placed before the volume data node.
• Plane normal:
  The "polarity" of the plane normal (for example whether it is +Z or -Z) doesn't affect rendering the oblique slice. However it's very important if you also use that plane to define a clipping plane. The clipping plane will clip away everything on the side of the plane opposite the normal vector direction. So to clip away the "front" (+Z) of the volume set the normal to 0,0,-1.
• Picking:
  The entire slice is pickable, even where it is transparent as a result of the current transfer function. The SoObliqueSliceDetail class allows you to get the voxel position and value after picking.
• Dragging:
  It is possible to interactively translate and rotate slices using an Open Inventor dragger, e.g. SoTranslate1Dragger. However the dragger's field values must be converted to an SbPlane. For a dragger that has a convenient "plane" field that can be directly connected, see the ClipPlaneDragger article in the Resources section of the Open Inventor Forum: http://forum.openinventor.com/showthread.php?t=733 (registration is required to view this section of the forum).
• Interpolation:
  Interpolation is specified using the interpolation field. The default (LINEAR) does bi-linear interpolation between voxel values. The NEAREST value can be used to display individual voxels. For best image quality we recommend using the TRILINEAR or MULTISAMPLE_12 value.
• Data range:
  By default VolumeViz maps the entire range of the voxel's data type (e.g. 0..65535 for unsigned short) into the colormap. This is often correct for byte (8 bit) voxels, but seldom correct for 16 bit voxels and never correct for floating point voxels. Use an SoDataRange node to specify the actual (or desired) range of data values to be mapped. Also use an SoDataRange node to implement brightness/contrast control like the Window/Level setting commonly used with medical images.
• Clipping:
  Volume primitives can be clipped using a region of interest (SoROI), geometry (SoVolumeClippingGroup) and/or height fields (SoUniformGridClipping). They are also clipped by OpenGL clipping planes (SoClipPlane), but we recommend using the VolumeViz clipping nodes instead.
• Material:
  The color of each voxel is modulated by the current diffuse color in the traversal state. The default diffuse color is 0.8,0.8,0.8. This results in full intensity values in the color map being displayed as 80% intensity. Therefore we recommend adding an SoMaterial node before the slice and setting its diffuseColor field to full white (1,1,1).
• Transparency:
  
  
  • Typically the color map (SoTransferFunction) used for volume rendering (SoVolumeRender) assigns transparency (alpha < 1) to some voxel values. If you want to use the same color map for slice rendering, but render the slice completely opaque, set the alphaUse field to ALPHA_OPAQUE. This overrides the alpha values in the color map (or an RGBA volume). However it does not affect transparency assigned using an SoMaterial node.
    
    
  • If you want to adjust the overall transparency of the slice, add an SoMaterial node and set its transparency field (keeping alphaUse set to ALPHA_AS_IS). Effectively a scale factor 1-transparency is applied to each voxel's alpha value.
    
    
  • Intersecting transparent slices cannot be rendered correctly by the basic blending transparency algorithms. To render this case correctly, set the transparency algorithm to SORTED_PIXEL using the viewer class or SoGLRenderAction.
• Voxel edges:
  The edges of the voxels can also be rendered. See options in the SoVolumeRenderingQuality node.
• Custom shaders:
  The current SoVolumeShader node, if any, allows custom shaders to be defined for special computation or rendering effects, including blending multiple volumes.
• Composition with Multiple Data:
  It is possible to compose datasets that have different dimensions, tile sizes and transformations.
  In order to help fetch the correct data values in custom shaders, texture coordinates conversion functions are provided in the VolumeViz/vvizStructure.h shader include.
  For instance,

  vec3 VVizTextureToTextureVec(in VVizDataSetId datasetSrc, in VVizDataSetId datasetDst, in vec3 texCoord);

  can be used to convert texture coordinates related to one dataset to texture coordinates related to another dataset.
  The conversion is based solely on the transformations applied to each dataset, which are defined by their model matrix and their extent.
  Please note that the model matrix of a dataset is defined by to the SoTransformation nodes that are placed before the SoDataSet node in the order of the traversal.
• Performance:
  
  • Tile size:
    For backward compatibility, the default tile size is still only 64. This is quite small for modern CPU/GPU hardware. The smaller the tile size, the larger the total number of tiles that must be managed by VolumeViz. This overhead can be significant, especially for operations that require reloading the data textures on the GPU, for example, changing the data range (SoDataRange). For smaller volumes, like 512^3, it can be efficient to set the tile size large enough to contain the entire volume. For very large volumes, larger tile sizes are efficient for SoVolumeRender but somewhat inefficient for slice rendering because complete tiles must be loaded even though the slice only uses part of the data. Applications should experiment.
    For volumes stored in LDM file format, the tile size must be specified when the volume is converted to LDM (see SoConverter and the "-t" option). For other data data formats the tile size can be specified using the SoVolumeData node's ldmResourceParameters field, but only after setting the filename field or calling the setReader() method.
    
    
  • LDM_USE_IN_MEM_COMPRESSION
    VolumeViz always manages data as "tiles", regardless of the data format. In many cases VolumeViz must create (or uncompress) the tiles at run time. These cases include in-memory volumes, any volume reader that does not implement the readTile() method (this includes all built-in formats except LDM, e.g. DICOM, SEGY, ...) and compressed LDM format files. If this variable is true (the default), VolumeViz only keeps a small cache of created/uncompressed tiles in CPU memory. If a tile's data is needed and that tile is not in the cache, the tile must be recreated. This overhead can be significant, especially for operations that require recreating all the data textures on the GPU, for example changing the data range (SoDataRange). We recommend setting this variable to false (see SoPreferences) unless saving CPU memory is critical.

EXAMPLE

For simple data sets, a basic VolumeViz rendering could be achieved with only a few nodes: minimally an SoVolumeData node to identify the data set and one rendering node. However most data sets need at least some of the additional nodes shown here in order to get a correct and useful rendering. Most applications will need additional nodes to take advantage of region of interest, interaction, clipping and other VolumeViz features. Please consider the code shown here as simply a guideline and a starting point for exploring the many powerful features available in Open Inventor.

Note that some of the property nodes (data, material, color map, etc) will typically be shared by multiple rendering nodes. In other words the volume usually only needs to be loaded once, using a single SoVolumeData node, then multiple slices and/or regions can be rendered using that data node.

Also note that this example is for a data volume, where each voxel can be considered a discrete sample from a continuous data field and interpolation should be used to compute values between voxel centers. If you are rendering a label volume, then each voxel is an "id" assigning that voxel to a specific material, object, etc. In this case, set the interpolation field to NEAREST to disable interpolation.

// Default setting can be a performance bottleneck
SoPreferences::setValue( "LDM_USE_IN_MEM_COMPRESSION", "0" );
 
// Keep volume viz separate from geometry
SoSeparator* volSep = new SoSeparator();
  root->addChild( volSep );
 
// Load volume data
SoVolumeData* volData = new SoVolumeData();
  volData->fileName = "$OIVHOME/examples/data/VolumeViz/3DHead.vol";
  volSep->addChild( volData );
 
// Set range of data values to visualize.
// Not required for 8-bit voxels, critical for larger data types.
// The getMinMax() call may be expensive for non-LDM file formats.
SoDataRange* volRange = new SoDataRange();
  if (volData->getDatumSize() > 1) {
    double minVal, maxVal;
    volData->getMinMax( minVal, maxVal );
    volRange->min = minVal;
    volRange->max = maxVal;
  }
  volSep->addChild( volRange );
 
// Load opaque intensity ramp
SoTransferFunction* volTF = new SoTransferFunction();
  volTF->predefColorMap = SoTransferFunction::INTENSITY;
  volSep->addChild( volTF );
 
// Display slice at full intensity
SoMaterial* volMat = new SoMaterial();
  volMat->diffuseColor.setValue( 1, 1, 1 );
  volSep->addChild( volMat );
 
// Remove tile boundary artifacts while moving. 
SoVolumeShader* volShader = new SoVolumeShader();
  volShader->interpolateOnMove = TRUE;
  volSep->addChild( volShader );
 
// Display a Z axis slice at center of volume
SoObliqueSlice* slice = new SoObliqueSlice();
  SbBox3f volext = volData->extent.getValue();
  SbVec3f center = volext.getCenter();
  slice->plane         = SbPlane( SbVec3f(0,0,1), center[2] );
  slice->interpolation = SoObliqueSlice::MULTISAMPLE_12;
  volSep->addChild( slice );

FILE FORMAT/DEFAULT

ObliqueSlice {

dataSetId	0
plane	0, 0, 1, 0
interpolation	LINEAR
alphaUse	ALPHA_BINARY
useRGBA	FALSE
alternateRep	NULL
enableBumpMapping	FALSE
bumpScale	1.0

}

ACTION BEHAVIOR

SoGLRenderAction
Draws a textured polygon based on current SoVolumeData, SoTransferFunction, and SoROI nodes.

SoGetBoundingBoxAction
Computes the bounding box that encloses the slice.

SEE ALSO

SoVolumeData, SoDataRange, SoTransferFunction, SoROI, SoSlice, SoOrthoSlice, SoVolumeShader

Definition at line 414 of file SoObliqueSlice.h.

Constructor & Destructor Documentation

SoObliqueSlice()

SoObliqueSlice::SoObliqueSlice

(

)

Constructor.

Member Function Documentation

getClassTypeId()

static SoType SoObliqueSlice::getClassTypeId ( )

static

Returns the type identifier for this class.

getTypeId()

virtual SoType SoObliqueSlice::getTypeId ( ) const

virtual

Returns the type identifier for this specific instance.

Reimplemented from SoSlice.

Reimplemented in ObliqueSliceBorder.

Friends And Related Symbol Documentation

SoObliqueSliceLdm

friend class SoObliqueSliceLdm

friend

Definition at line 543 of file SoObliqueSlice.h.

Member Data Documentation

dataSetId

SoSFInt32 SoObliqueSlice::dataSetId

Specifies the SoVolumeData node to use.

This is useful when datasets of different dimensions are present in the scene graph. Please see SoMultiDataSeparator for more details.

When set to 0, the last SoVolumeData node on state is used. Default is 0.

NOTE: field available since Open Inventor 10.11.0

Definition at line 430 of file SoObliqueSlice.h.

plane

SoSFPlane SoObliqueSlice::plane

Plane defining the slice.

The default plane corresponds to the XY plane.

Definition at line 435 of file SoObliqueSlice.h.

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

• VolumeViz/nodes/SoObliqueSlice.h