SoVolumeRender Class Reference
[Nodes]

VolumeViz Renders a data volume using direct volume rendering More...

#include <VolumeViz/nodes/SoVolumeRender.h>

Inheritance diagram for SoVolumeRender:
SoVolumeShape SoLdmShape SoShape SoNode SoFieldContainer SoBase SoRefCounter SoTypedObject

List of all members.

Public Types

enum  LowResMode {
  DECREASE_NONE = 1,
  DECREASE_SLICES = 1 << 1,
  DECREASE_SCREEN_RESOLUTION = 1 << 2
}
enum  NumSlicesControl {
  ALL,
  MANUAL,
  AUTOMATIC,
  MAIN_AXIS
}
enum  RenderMode {
  VOLUME_RENDERING = 0,
  MIN_INTENSITY_PROJECTION,
  MAX_INTENSITY_PROJECTION,
  SUM_INTENSITY_PROJECTION,
  AVERAGE_INTENSITY_PROJECTION
}
enum  SamplingAlignment {
  VIEW_ALIGNED = 0,
  DATA_ALIGNED,
  BOUNDARY_ALIGNED,
  SMOOTH_BOUNDARY_ALIGNED
}
enum  AbortCode {
  CONTINUE,
  ABORT,
  SKIP
}
typedef AbortCode SoVolumeRenderAbortCB (int totalElems, int thisElem, void *userData)

Public Member Functions

virtual SoType getTypeId () const
 SoVolumeRender ()
void setRenderProgress (SoProgressIndicator *ps)
void setAbortCallback (SoVolumeRenderAbortCB *func, void *userData=NULL)

Static Public Member Functions

static SoType getClassTypeId ()

Public Attributes

SoSFEnum numSlicesControl
SoSFInt32 numSlices
SoSFBitMask lowResMode
SoSFInt32 lowScreenResolutionScale
SoSFBool subdivideTile
SoSFBool fixedNumSlicesInRoi
SoSFInt32 projectedTileSubdivision
SoSFBool opacityCorrection
SoSFEnum renderMode
SoSFEnum samplingAlignment
SoSFFloat opacityThreshold

Friends

class SoVolumeRenderInterface
class SoVolumeRenderLdm
class SoVolumeRenderRaycast

Deprecated



SoDEPRECATED SoSFBool lighting
SoDEPRECATED SoSFVec3f lightDirection
SoDEPRECATED SoSFFloat lightIntensity
SoDEPRECATED SoSFBool viewAlignedSlices

Detailed Description

VolumeViz Renders a data volume using direct volume rendering

This node renders volume data using "direct volume rendering". The volume process involves sampling, interpolation, classification and composition. By default the rendering algorithm is a GPU-based technique called raycasting. Raycasting has similarities to the well known algorithm called raytracing, but is specialized for volume data (renders voxels not triangles) and does not currently implement reflection or refraction. One or more "rays" are cast through the volume from each relevant pixel on the screen. Samples are taken at intervals along each ray. The sample interval is controlled by the numSlices and numSlicesControl fields At each sample point a value is interpolated from the closest voxels. The interpolation technique is controlled by the interpolation field. Classification means that color and opacity are computed based on the current SoDataRange and SoTransferFunction (and possibly values from other volumes - see SoVolumeShader). Optional rendering effects may modify the base color and/or opacity. These effects are controlled by an SoVolumeRenderingQuality node and include lighting, shadows, edge coloring, boundary opacity and more. The sample is then composited with other samples along the ray. Composition is controlled by the renderMode field. By default colors are combined based on the opacity of the sample (alpha blending). The ray is terminated if it reaches full opacity or reaches the current depth in the depth buffer.

For a volume containing scalar data values, each voxel's basic RGBA value is determined by the current SoDataRange and SoTransferFunction nodes. This value is combined with current diffuse color and transparency (set, for example, with an SoMaterial node). This means that, for example, the current transparency can be used as a global alpha scale factor to decrease the opacity of all voxels. By default, scalar values are loaded on the GPU and the GPU interpolates between the data values before applying the color map. See the interpolation field for options. To force RGBA values to be loaded (implies color map is applied on the CPU and GPU interpolates between color values), see the usePalettedTexture field in the SoVolumeData node.

For an RGBA volume, each voxel's base RGBA value comes directly from the volume data (SoDataRange and SoTransferFunction are ignored). However if lighting is enabled, the final voxel color is also affected by the emissiveColor, specularColor and shininess fields of SoMaterial.

The samplingAlignment field controls whether the samples are axis aligned (perpendicular to one axis of the volume), view aligned (perpendicular to the view direction) or boundary aligned (each ray starts at the first intersected voxel with alpha value > 0). Generally boundary aligned slices should be used (better image quality). Using SoVolumeGroup, SoVolumeIsoSurface or SoProjection nodes will automatically switch to view-aligned samples.

The property nodes SoVolumeIsoSurface and SoVolumeDataDrawStyle add additional rendering styles and can be used, for example, to force SoVolumeRender to draw a GPU computed isosurface instead of volume rendering.

Example rendering:

lighting = FALSE lighting = TRUE
lightoff.jpg
lighton.jpg
composition = ALPHA_BLENDING composition = MAX_INTENSITY
compalpha.jpg
compmax.jpg

Multiple volumes:

VolumeViz provides several mechanisms for combining or rendering multiple volumes, depending on the application's specific requirements. There are several cases:

Custom shaders:

The SoVolumeShader node allows a variety of custom shader functions to be defined for special computation or rendering effects on single volumes or multiple volumes. All of these features require programmable shader support on the GPU. Be sure to use an SoMultiDataSeparator (instead of SoSeparator) when combining multiple volumes.

Lighting:

The SoVolumeRenderingQuality property node allows you to to enable GPU computed lighting based on the first SoLight node in the scene graph. (Note that this is typically the viewer's "headlight".) VolumeViz supports two lighting algorithms. They are both computed on the GPU and are independent (but normally only one should be enabled).

Warning: CPU computed lighting can be enabled using the lighting field in this node. In this case the lightDirection and lightIntensity fields control the light. Note that when lighting is computed on the CPU, RGBA textures are loaded on the GPU, so color map changes generally require re-loading all the data textures. NOTE: This feature is obsolete. Use SoVolumeRenderingQuality::lighting instead.
Gradient lighting Deferred lighting
Lighting_gradient.png
Lighting_deferred.png

Shadows:

Open Inventor shadow rendering works for volume rendering similar to any other geometry. When shadow rendering is enabled (see SoShadowGroup), non-transparent voxels can cast and receive shadows (see SoShadowStyle). Shadow rendering is independent of whether lighting is enabled for the volume.

SoVolumeRender also supports "ambient occlusion" rendering (see ambientOcclusion field in SoVolumeRenderingQuality). This rendering mode is visually a kind of self-shadowing and represents an approximation of the effect of ambient global lighting in the scene. Ambient occlusion can be combined with gradient or deferred lighting and with shadow casting.

Shadow casting Ambient occlusion
Lighting_shadows.png
Lighting_ambientOcclusion.png

Clipping:

VolumeViz provides multiple tools for clipping volume rendering. Any or all of these tools may be combined for more complex clipping situations. Note that these tools clip all volume shapes including slices.

Picking:

SoRayPickAction handles picking of VolumeViz shapes similar to other geometry in the scene, but with additional features. Picking on an SoVolumeRender node can return the first non-transparent voxel "hit" or the entire set of intersected voxels along the pick ray. Similar to other geometry, SoPickedPoint can return a "detail" class specific to SoVolumeRender. SoVolumeRenderDetail returns the IJK (voxel coordinate) position of the pick and the data value at that point.

Since Open Inventor 8.6, the SoVolumeRender node (by default) uses the GPU to compute the picked voxel during an SoRayPickAction. For this to work, the SoRayPickAction must have its scene manager initialised using the method SoAction::setSceneManager(). SoHandleEventAction does this automatically, so it is not necessary for the application to take any action when using (for example) an SoEventCallback node and calling the getPickedPoint() method. However if the application creates its own SoRayPickAction then it should set the scene manager. If no scene manager is specified, a warning message is issued and software picking is done. If necessary, using the GPU for volume picking may be disabled by setting the environment variable IVVR_GPU_PICKING to 0 (see SoPreferences).

Projection:

The SoVolumeRender node supports projected volume rendering, for example rendering a volume defined on a grid of latitude / longitude coordinates. Projection is enabled by adding an SoProjection node before the SoVolumeRender node (see SoProjection for more information about supported coordinate systems, ellipsoids and map projections). The projection quality versus speed ratio can be controlled using the new projectedTileSubdivision field that defines how often each tile's geometry will be subdivided when projected. This is important because only the corner points of the tiles are projected, not the individual voxels. So subdividing the tiles provides a better approximation of the actual shape of the grid. Volume projection works with both regular (uniform voxel spacing) and rectilinear (non-uniform voxel spacing) grids. SoProjection automatically selects view-aligned sampling.

Warning:

Performance:

Volume rendering performance is affected by many factors including the size of the volume and the rendering options selected. Image quality is also affected by many rendering options and, in general, higher quality implies lower performance. Some of the factors affecting volume rendering performance are:

VolumeViz keeps tiles from a compressed LDM format file in CPU memory as compressed data. This option allows more tiles to be kept in the same amount of CPU memory, but incurs a performance penalty because a tile must be uncompressed when its data is needed, unless it is found in a small cache of uncompressed tiles (see SoBufferObject::getBufferObjectCache). This penalty is particularly noticeable for operations that require recreating data textures on the GPU, for example changing the data range (SoDataRange).

If rendering performance is too slow, it may be necessary to render with high quality settings when the user is not interacting with the scene, but temporarily switch to high performance (lower quality) settings when the user is interacting. Open Inventor automatically sets "interactive mode" when the user is moving the camera or moving a dragger. The application can explicitly set interactive mode, for example while the user is moving a slider in the user interface. Some important tools are:

Limitations:

EXAMPLE

Label volumes

A label volume, also known as a label field, is usually the result of doing some sort of segmentation on a data volume. Each voxel value is an integer label (id) identifying which material, object, etc that the voxel belongs to. There could be 100's or 1000's of labels, but there might be as few as 8 label values. For example, a simple label volume might have 7 opaque materials plus plus an "exterior" material which is completely transparent. Conceptually, there is one big difference between a (typical) data volume and a label volume. A data volume is conceptually a set of discrete samples taken from a continuous scalar field. So we know the exact value at the center of each voxel and interpolate between those values to get the value at any position in between voxels. In a label volume we normally consider each voxel to belong completely to one material, so the value is constant until we cross the boundary into the next voxel. Therefore we do not want to interpolate the label values.
When rendering a label volume, make the following changes to the above example:
If rendering isosurfaces (SoVolumeIsosurface), set the SoVolumeRenderingQuality segmentedInterpolation field to TRUE.
It is also important to set the data range, texture precision and color map size carefully. Please see the label volume discussion in SoTransferFunction.

FILE FORMAT/DEFAULT

ACTION BEHAVIOR

SEE ALSO

SoVolumeData, SoTransferFunction, SoROI, SoVolumeShader, SoVolumeIsosurface, SoVolumeRenderingQuality, SoProjection, SoVolumeRendering, SoUniformGridClipping, SoVolumeClippingGroup, SoInteractiveComplexity

See related examples:

DenoisingImage3D, MedicalDentalCurveUnfolding, MedicalDicomReader, MedicalMPRViewer, MedicalGL_VolumeRender, MedicalMultiChannel, MedicalVolumeTextureCompose, MedicalAmbientOcclusion, MedicalDeferredLighting, Medical4DVolumeRendering, MedicalAnatomicalViews, MedicalDTIViewer, MedicalVolumeDataDrawStyle, MedicalFreeHandCutting, MedicalMarchingCubesSurface, MedicalSegmentation, MedicalSimpleVolumeMask, MedicalVolumeExtract, MedicalVolumePipeClipping, MedicalBonesMuscles, MedicalSimpleVolumeAxis, MedicalVolumePickingGpu, MedicalColorMap, MedicalMultiTransferFunctions, MedicalMPRViewerRemote, BonesMuscles, VVIZ-Template-SG, AmbientOcclusion, ColorMap, CSGClippingGroup, DataAccessCustomReader, DataTransform, DeferredLighting, GL_VolumeRender, HorizonClipping, MultiChannel_ex1, MultiChannel_ex2, SimpleInteractiveParameters, SimpleShader, SimpleVolume, SimpleVolumeAxis, VolumeExtract, VolumePickingGpu, VolumePipeClipping, VolumeTransform, VolRend


Member Typedef Documentation

typedef AbortCode SoVolumeRender::SoVolumeRenderAbortCB(int totalElems, int thisElem, void *userData)

Member Enumeration Documentation

Abort code for callback.

Enumerator:
CONTINUE 

Continue rendering as usual.

ABORT 

The render action of the SoVolumeRender node is aborted.

The render action continues for the remaining part of the scene graph.

SKIP 

The current slice is not drawn.

Rendering continues with the next slice.

Method to use when moving in low resolution.

Used with lowResMode field.

Enumerator:
DECREASE_NONE 

No low resolution mode when moving.

DECREASE_SLICES 

Decrease the number of samples according to SoComplexity::value when moving.

It has no effect if numSlicesControl is set to AUTOMATIC because this mode always uses the SoComplexity node to compute the number of samples to draw.

DECREASE_SCREEN_RESOLUTION 

Downscale the screen resolution of the volume when moving by the factor defined in lowScreenResolutionScale.

Number of samples control mode.

Used with numSlicesControl field.

Enumerator:
ALL 

Use all samples
The number of samples depends on the viewing direction.

MANUAL 

Use the number of samples specified by the numSlices field.

The number of samples does not depend on the viewing direction.

AUTOMATIC 

(Recommended) Use a number of samples computed as follows:
If numSlices is greater than zero, then
n = complexity * 2 * numSlices
where complexity comes from the value of field SoComplexity::value and numSlices comes from the numSlices field.

The number of samples does not depend on the viewing direction.

If numSlices is any value less than or equal to 0, the dimension of the volume data is used instead of numSlices, so
n = complexity * 2 * volumeDimension
The number of samples depends on the viewing direction.

The factor 2 is used because by default complexity is equal to 0.5. So, by default, the behavior for numSlices greater than zero is the same as MANUAL and the default behavior for numSlices less than or equal to zero is the same as ALL.
You can increase the complexity up to 1.0, which would double the number of samples used. You can decrease the complexity to reduce the number of samples used. The global alpha is corrected so that the brightness looks the same.

MAIN_AXIS 

Use a number of samples computed as follows:
n = complexity * 2 * volumeDataDimension[mainVisibleAxis]
where complexity comes from the value of field SoComplexity::value.

The number of samples depends on the viewing direction.
NOTE: enumeration value available since Open Inventor 8.1

Composition mode.

See the renderMode field. NOTE: enumeration value available since Open Inventor 9.1

Enumerator:
VOLUME_RENDERING 

Alpha compositing (Default).

MIN_INTENSITY_PROJECTION 

Minimum intensity projection (MinIP).

The minimum value found along each ray is used to determine color.

MAX_INTENSITY_PROJECTION 

Maximum intensity projection (MIP).

The maximum value found along each ray is used to determine color.

SUM_INTENSITY_PROJECTION 

Ray sum intensity projection (RSP).


The values found along each ray are accumulated. Then the total value is normalized by the nominal number of samples for every ray (see numSlices), which is the same for all rays. The values seen in shader functions, e.g. VVizComputeFragmentColor are still in the range 0..1, but the range of values that represents is quite different from the voxel data range.

AVERAGE_INTENSITY_PROJECTION 

Average Intensity projection (AIP).


The values found along each ray are accumulated. The total value is divided by the actual number of samples along the current ray. The actual number of samples may be different for each ray. The resulting data range will be similar to the voxel data range but not necessarily the same. If there are many low, e.g. 0, valued voxels, the average may be very small.

Sampling alignment.

Used with the samplingAlignment field. NOTE: enumeration value available since Open Inventor 9.1

Enumerator:
VIEW_ALIGNED 

Samples are located on planes perpendicular to the view direction.

DATA_ALIGNED 

Samples are located on planes perpendicular to one axis of the volume.

BOUNDARY_ALIGNED 

Samples are located on shells aligned with the volume's internal "boundary".

Each ray begins sampling at the first intersected voxel that has an alpha value > opacityThreshold.

SMOOTH_BOUNDARY_ALIGNED 

Similar to BOUNDARY_ALIGNED but uses a cubic interpolation to compute the boundary, giving smoother results when using SoVolumeRenderingQuality::deferredLighting.

When using linear interpolation and deferred lighting, BOUNDARY_ALIGNED can generate "flat shading" due to linear interpolation between voxels. SMOOTH_BOUNDARY_ALIGNED will generate a smooth shading using a cubic interpolation to find the volume's boundary and use a linear interpolation for the rest of volume. This is a good compromise between result and performances of a full tricubic interpolation. Please refer to SoVolumeRenderingQuality::deferredLighting and SoVolumeShape::interpolation for details. LIMITATIONS SMOOTH_BOUNDARY_ALIGNED is not supported in the following case:


Constructor & Destructor Documentation

SoVolumeRender::SoVolumeRender (  ) 

Constructor.


Member Function Documentation

static SoType SoVolumeRender::getClassTypeId (  )  [static]

Returns the type identifier for this class.

Reimplemented from SoVolumeShape.

virtual SoType SoVolumeRender::getTypeId (  )  const [virtual]

Returns the type identifier for this specific instance.

Reimplemented from SoVolumeShape.

void SoVolumeRender::setAbortCallback ( SoVolumeRenderAbortCB func,
void *  userData = NULL 
)

Sets callback to call during texture map rendering to test for an abort condition.

When not in raycasting mode, it will be called for each element that is rendered.

In the case of LDM, an element is a tile, totalElems is the number of tiles that will be drawn, and thisElem is the number (counting from one) of the next tile to be drawn. The quotient thisElem / totalElems represents the progress of the volume rendering process.

In the non-LDM case, an element is a slice, totalElems is the number of slices that will be drawn, and thisElem is the number (counting from one) of the next slice to be drawn. The quotient thisElem / totalElems represents the progress of the volume rendering process.

This allows applications to terminate rendering of this node prematurely if some condition occurs. It does not terminate traversal of the scene graph. (For that use the SoGLRenderAction abort callback.) The callback function should return one of the AbortCode codes to indicate whether rendering should continue.

void SoVolumeRender::setRenderProgress ( SoProgressIndicator ps  )  [inline]

Set an application defined SoProgressIndicator object which will raise an event before and after the volume 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.

This method is useful to track loading time of the first frame when SoLDMResourceParameters::fixedResolution is set to TRUE.

If set to NULL no events will be raised. Default is NULL.

Since Open Inventor 9.9


Friends And Related Function Documentation

friend class SoVolumeRenderInterface [friend]
friend class SoVolumeRenderLdm [friend]
friend class SoVolumeRenderRaycast [friend]

Member Data Documentation

When this field is set to FALSE (the default), the number of samples set by numSlices is the number of samples used for the region defined by the current ROI.

Therefore the number of samples may change when the ROI size changes. When TRUE, numSlices is the number of samples for the whole volume. In this case the sample density is constant, independent of the ROI size. Default is FALSE.

NOTE: field available since Open Inventor 7.1

Light direction (relative to the volume).

The default is (-1,-1,-1). Only affects CPU computed lighting (i.e. when the lighting field is TRUE).

Deprecated:

Deprecated since Open Inventor 8500
Use SoVolumeRenderingQuality::lighting field instead.

Indicates if lighting is required.

Default is FALSE.
NOTE: Better performance for lighting can be obtained using the SoVolumeRenderingQuality node. Using SoVolumeRenderingQuality, lighting is determined by the first light in the scene graph (similar to other geometry) and the lighting computation is done on the GPU (therefore SoVolumeRenderingQuality requires programmable shaders).

Using the lighting field, lighting is determined by the lightDirection field and the lighting computation is done on the CPU. This requires RGBA textures to be loaded on the GPU which uses more texture memory and requires more time to modify the transfer function (color map) because textures must be reloaded. Note that activating or deactivating lighting will also normally force the textures to be recreated, which may be slow.

NOTE: Only set the lighting field to TRUE in SoVolumeRenderingQuality or SoVolumeRender. Do not set both lighting fields to TRUE.

Deprecated:

Deprecated since Open Inventor 8500
Use SoVolumeRenderingQuality::lighting field instead.

Light intensity in the range [0-1].

The default is 1. Only affects CPU computed lighting (i.e. when the lighting field is TRUE).

Deprecated:

Deprecated since Open Inventor 8500
Use SoVolumeRenderingQuality::lighting field instead.

Sets the method to use when moving in low resolution.

Use enum LowResMode. Default is DECREASE_NONE.

  • DECREASE_NONE: Default. Do not use low resolution mode when moving (i.e., when the viewer is moving the camera).
  • DECREASE_SLICES: Decrease the number of samples according to SoComplexity::value when moving. It has no effect if numSlicesControl is set to AUTOMATIC because in this case, VolumeViz always uses the SoComplexity node to compute the number of samples.

If lowResMode is DECREASE_SCREEN_RESOLUTION, render the volume at a lower screen resolution.

when moving. The resolution used is the current screen resolution divided by lowScreenResolutionScale. Default is 1. A value of 2 or 4 is recommended if using this option.

NOTE: field available since Open Inventor 7.0

Specifies the number of samples along each ray.


The default is -1, which means to use the volume dimensions (number of voxels on each axis) when the numSlicesControl field is set to AUTOMATIC.

NOTE: This value is not used if the numSlicesControl field is set to ALL (the default for that field).

Controls how the number of samples along each ray is determined.


Use enum NumSlicesControl. Default is AUTOMATIC. Generally increasing the number of samples will increase the image quality, but decrease the performance (frames per second).

Since Open Inventor 9.2, we recommend to set the numSlicesControl field to AUTOMATIC and the numSlices field to 0. The number of samples will be computed based on the dimensions of the volume (number of voxels on each axis), the SoComplexity::value setting and the viewing direction. If the viewing direction changes, the number of samples will be automatically adjusted.

Controls whether opacity correction is done.


If TRUE, opacity is automatically adjusted to give similar appearance no matter how many samples are used. If FALSE, opacity is not corrected and increasing the number of samples will increase the opacity. Default is TRUE.

Generally this field should always be set to true. NOTE: field available since Open Inventor 8.1

Specifies a threshold opacity (alpha) value that defines voxels considered to be "solid" (non-transparent).

Many volume data sets are composed of objects of interest floating in an approximately transparent "fog", depending on opacity values in the transfer function. Several effects like BOUNDARY_ALIGNED sampling, ambientOcclusion and deferredLighting need to locate the boundary between solid objects and ambient fog. This field defines a threshold in the range [0, 1]. Voxels are considered solid if their alpha value is greater than opacityThreshold.

A value of 0.0 generally works well with a transfer function containing "binary" opacity (a transfer function with only fully transparent or fully opaque colors). If this is not the case, you should set this value according to your visualization parameters. Generally between 0.1 and 0.5.

Default is 0.1, Ignore low visibility voxels.

NOTE: field available since Open Inventor 9.3

When doing volume projection (see SoProjection), only the geometry (corner vertices) of the LDM tiles are projected, not the individual voxels.

This can produce an imprecise projected volume when using large LDM tiles or low resolution levels (where the LDM tiles are larger).

This field controls how many times the tile geometry will be subdivided (producing more vertices) before being projected. Subdivision gives a smoother, more accurage shape, but requires much more computational power and may reduce rendering performance. Default is 1 (subdivide once).

NOTE: This field is ignored in raycasting mode (the default).



NOTE: field available since Open Inventor 7.1

Specifies the composition mode.

Composition controls how the voxels along each sampling ray are combined to form the final image. Use enum RenderMode. Default is VOLUME_RENDERING (alpha blending).

VOLUME_RENDERING blends the R, G, and B components for each data value along the sampling ray based on the alpha value (alpha blending).

MIN_INTENSITY_PROJECTION draws only the color associated with the minimum data intensity along the sampling ray.

MAX_INTENSITY_PROJECTION draws only the color associated with the maximum data intensity along the sampling ray.

SUM_INTENSITY_PROJECTION draws only the color associated with the sum of all data values along the sampling ray. The values seen in shader functions, e.g. VVizComputeFragmentColor are still in the range 0..1, but the range of values that represents is quite different from the voxel data range.

AVERAGE_INTENSITY_PROJECTION draws only the color associated with the average of all data values along the sampling ray. If there are many low, e.g. 0, valued voxels, the average may be very small. You may be able to use SoROI (Region of Interest) to remove some of these voxels.

Note: When using a renderMode other than VOLUME_RENDERING (alpha blending):

NOTE: field available since Open Inventor 9.1

Specifies which technique to use to align rayCast samples.

Use enum SamplingAlignment. Default is BOUNDARY_ALIGNED.

VIEW_ALIGNED: Samples are located on planes perpendicular to the view direction.

samplingAlignment_VIEW_ALIGNED.png

DATA_ALIGNED: Samples are located on planes perpendicular to one axis of the volume.

samplingAlignment_DATA_ALIGNED.png

BOUNDARY_ALIGNED: Samples are located on shells aligned with the volume's internal "boundary". Each ray begins sampling at the first intersected voxel that has an alpha value > opacityThreshold. This technique greatly decreases "slicing" artifacts even with a relatively small number of slices. It is strongly recommended to enable this mode when using SoVolumeRenderingQuality::ambientOcclusion.

samplingAlignment_BOUNDARY_ALIGNED.png

SMOOTH_BOUNDARY_ALIGNED: Similar to BOUNDARY_ALIGNED but uses a cubic interpolation to compute the boundary, giving smoother results when using SoVolumeRenderingQuality::deferredLighting.

NOTE: If an SoVolumeGroup or SoProjection node applies to this node, the field is ignored and VIEW_ALIGNED is used.

NOTE: field available since Open Inventor 9.1

If true, LDM tiles will be subdivided for rendering.

Fully transparent sub-tiles won't be rendered, thus (potentially) increasing the speed of the rendering if an expensive shader is being used and significant regions of the volume are fully transparent. However using false is faster if the user will frequently change the data range (e.g. window center/width in medical applications). SubTileDimension can be changed using SoVolumeData node's ldmResourceParameters field. Default is FALSE.

See the 'subtileDimension' field in SoLDMResourceParameters. If the tileDimension is larger than the default value, then the subtileDimension should also be larger to avoid performance issues.



NOTE: field available since Open Inventor 7.0

Indicates if samples should be computed in a view-aligned manner.

Default is TRUE.

NOTE: If an SoVolumeIsosurface, SoVolumeRenderingQuality or SoProjection node applies to this node, this field is ignored and view-aligned samples are used.

Deprecated:

Deprecated since Open Inventor 9100
Use samplingAlignment field instead.

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

Open Inventor Toolkit reference manual, generated on 12 Sep 2019
Copyright © Thermo Fisher Scientific All rights reserved.
http://www.openinventor.com/