SoOffscreenVolumeRender Class Reference
[Nodes]

Extract data from an SoVolumeRender More...

#include <VolumeViz/nodes/SoOffscreenVolumeRender.h>

Inheritance diagram for SoOffscreenVolumeRender:

List of all members.

Public Types
enum	Components {   ALPHA,   RGBA }
Public Member Functions
virtual SoType	getTypeId () const
	SoOffscreenVolumeRender ()
SbVec3i32	getMaxBoxSize (SoState *state=NULL)
SbBox3d	ijkToXyzBox (const SbBox3i32 &ijkBox)
bool	synchronousExtraction (SoSceneManager *sceneManager)
Static Public Member Functions
static SoType	getClassTypeId ()
Public Attributes
SoSFNode	volumerenderSceneGraph
SoSFNode	bboxSceneGraph
SoSFVec3i32	boxSize
SoSFBool	trigger
SoSFFloat	opacityThreshold
SoSFEnum	components
SoSFMatrix	dataSpaceMatrix

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Detailed Description

Extract data from an SoVolumeRender

The SoOffscreenVolumeRender node extracts data by rendering one or more volumes (via SoVolumeRender) into a buffer that can then be used for different computation tasks.

Volumes of interest are specified by a subscenegraph in volumerenderSceneGraph.

The region to be extracted is the bounding box of the scene graph specified in the bboxSceneGraph field.

To implement an extraction, the application must derive a new class from SoOffscreenVolumeRender and implement :

• the boxComputed method. This method is called with parameters that give access to information about the processed box.
• the getNextSubBox method. This method must return subBox size smaller than getMaxBoxSize. We recommend to request subbox even smaller in order to get more parallelism between extraction processing (done on GPU) and application processing and reduce peak GPU memory resources used.

The resolution of the extraction is controlled by boxSize field. As extraction is done using GPU techniques, there is a size limit on the boxSize that can be extract in one call. This limit can be retreived through getMaxBoxSize call.

Limitations:

• It is not possible to extract a volume displayed as an isosurface (via SoVolumeDataDrawStyle or SoVolumeIsosurface).
• SoResetTransform node usage should be avoided in volumeRenderSceneGraph or bboxSceneGraph scene graph, in order to get the best extraction precision even with very flat extraction box. In general it is possible to use SoTransformSeparator node instead.

FILE FORMAT/DEFAULT

SoOffscreenVolumeRender {

volumerenderSceneGraph	NULL
bboxSceneGraph	NULL
boxSize	(64, 64, 64)
trigger	FALSE
opacityThreshold	0
components	ALPHA

}

SEE ALSO

SoDataSet, SoVolumeData, SoVolumeRender

See related examples:

MedicalVolumeExtract, VolumeExtract

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Member Enumeration Documentation

enum SoOffscreenVolumeRender::Components

Enumerator:

ALPHA
RGBA

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Constructor & Destructor Documentation

SoOffscreenVolumeRender::SoOffscreenVolumeRender

(

)

Default constructor.

---

Member Function Documentation

static SoType SoOffscreenVolumeRender::getClassTypeId

(

)

[static]

Returns the type identifier for this class.

Reimplemented from SoNode.

SbVec3i32 SoOffscreenVolumeRender::getMaxBoxSize

(

SoState *

state = NULL

)

Returns the maximum boxSize that can be extract in one boxComputed for the current state.

virtual SoType SoOffscreenVolumeRender::getTypeId

(

)

const [virtual]

Returns the type identifier for this specific instance.

Reimplemented from SoNode.

SbBox3d SoOffscreenVolumeRender::ijkToXyzBox

(

const SbBox3i32 &

ijkBox

)

Convert ijk box coordinates returned by boxComputed method to the bboxSceneGraph space.

bool SoOffscreenVolumeRender::synchronousExtraction

(

SoSceneManager *

sceneManager

)

Does extraction synchronously, whereas using trigger field will execute extraction on next redraw.

Parameters:

sceneManager

the scene manager of the viewer scene to be extracted.

Returns:

TRUE on success.

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Member Data Documentation

SoSFNode SoOffscreenVolumeRender::bboxSceneGraph

Head of the scene graph that defines the 3D off-screen scene cube to consider in world coordinates.

SoSFVec3i32 SoOffscreenVolumeRender::boxSize

Resolution of the output data in the off-screen box.

SoSFEnum SoOffscreenVolumeRender::components

Components to get back from the offscreen render.

Use enum Components. Default is ALPHA.

SoSFMatrix SoOffscreenVolumeRender::dataSpaceMatrix

This transformation is applied on the volume render texture coordinate during the extraction.

It allows to change the extraction frame. This matrix is applied on normalized texture coordinates all components are between 0-1 and must be in [0-1] after the transformation. So to inverse an axis, we must apply the following transformation: -1*u+1 (where u is a texture coordinate) and not just a simple negative scale.

To swap I and J axis, the matrix would be:

 SbMatrix( 0, 1, 0, 0,
           1, 0, 0, 0,
           0, 0, 1, 0,
           0, 0, 0, 1);

To reverse I axis, the matrix would be:

 SbMatrix(-1, 0, 0, 0,
           0, 1, 0, 0,
           0, 0, 1, 0,
           1, 0, 0, 1);

To reverse J axis, the matrix would be:

 SbMatrix( 1, 0, 0, 0,
           0,-1, 0, 0,
           0, 0, 1, 0,
           0, 1, 0, 1);

To reverse K axis, the matrix would be:

 SbMatrix( 1, 0, 0, 0,
           0, 1, 0, 0,
           0, 0, -1, 0,
           0, 0, 1, 1);

SoSFFloat SoOffscreenVolumeRender::opacityThreshold

During extraction, voxels with an opacity less than the specified value will be ignored Default is 0.

Valid range is [0-1].

SoSFBool SoOffscreenVolumeRender::trigger

Setting this field to TRUE will start the off-screen rendering process.

This field is set to FALSE when computation is finished. Default is FALSE.

SoSFNode SoOffscreenVolumeRender::volumerenderSceneGraph

Head of the scene graph that contains one or multiple VolumeRender node to render in 3D off-screen cube.

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

• VolumeViz/nodes/SoOffscreenVolumeRender.h