- All Implemented Interfaces:
public class SoDataRange extends SoNodeRange of data values to be mapped to the color map. This node allows you to specify the range of scalar data values in a data set (
SoVolumeData) that will be mapped into the color map (
SoTransferFunction). When the volume data type is larger than the data type on the GPU, for example float data scaled to byte data, it also specifies the range of scalar data values that will be scaled to fit in the GPU data type.
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
SoDataRangenode to specify the actual (or desired) range of data values to be mapped. For example, a typical initial data range for DICOM data calibrated in Hounsfield units might be -1000 to 3000.
- The voxel value data type can be queried using the
- The number of bytes in a voxel value can be queried using the
- The actual min and max values for the data set can be queried using the
Note that this method might force VolumeViz to load the entire data set if the volume reader for that format does not implement the getMinMax query. Normally for an LDM format data set, the min and max values are stored in the LDM header. For a non-LDM data set, if a filename and/or reader have been specified and the data set has not yet been loaded, VolumeViz will load the entire data set to compute the min and max values. For a large data set this may take a long time.
- DICOM: The Window Center (0028,1050) and Window Width (0028,1051) values (if present in the data set) can be queried by using an
SoVRDicomDataobject obtained from the
SoVRDicomFileReaderor by using the MedicalHelper class. You can also use the MedicalHelper method dicomAdjustDataRange.
When using multiple volumes (see
SoMultiDataSeparator), a single
SoDataRangenode can be used to specify the data range for all volumes or each volume can have its own independent data range. In the second case, create one
SoDataRangenode for each volume and set the
dataRangeIdequal to the
SoDataSet.dataSetIdof the corresponding volume.
Note that the meaning of the min and max fields in
SoDataRangeis quite different than the meaning of the minValue and maxValue fields in
SoTransferFunction. The fields in
SoDataRangespecify the range of voxel values that will be mapped into the full color map. The fields in
SoTransferFunctionspecify the range of indices in the color map that will actually be used to store the color map. The visual effect changing these fields can be quite similar, but there are trade-offs to be aware of. Changing the
SoTransferFunctionfields is generally much faster and can be a useful approximation of changing the data range, but the resolution of the color map (the ratio of data values to color map entries) is reduced.
NOTE: Setting the min value greater than or equal to the max value will cause this node to be ignored.
Brightness and contrast:
Often the distribution of voxel values within the actual data range is not uniform and more details can be seen by adjusting thePerformance:
SoDataRangevalues to increase brightness and/or contrast. This is particularly true when using a gray scale color map (for example the predefined INTENSITY map in
SoTransferFunction). In medical imaging this range setting is often specified by the window center and window width.
The window center is the image intensity that will be displayed as a medium-gray and the window width is the range of data values between full black and full white. For example, if the data volume contains byte data with a native range of 0 to 255, the default data range (0 to 255) is effectively specifying a window center of 128 and width of 256. To increase contrast in the resulting image we might set a data range of 20 to 110, which makes the window center and width 65 and 90 respectively.
For larger data types, changing the data range may require VolumeViz to recreate the data textures on the GPU. This is necessary to maximize use of the available bits of precision on the GPU. Since Open Inventor 9.6, recreating data textures should not be required for 8 bit data or for 16 bit data when the
SoDataSet.texturePrecisionfield is set to 16.
Recreating data textures may be slow for larger volumes, even in the 512^3 range. There are several parameters that significantly affect this:
- 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
SoVolumeRenderbut 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
SoConverterand the "-t" option). For other data data formats the tile size should be specified after the
SoVolumeDatanode is created, using the ldmResourceParameters field, but before setting the filename field.
This environment variable (see
SoPreferences) affects much more than its name implies. 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 (all built-in formats except LDM) and compressed LDM format files. If this variable is true ( the default value), then VolumeViz only keeps a small cache of tiles in memory. See the
SoBufferObjectmethod getBufferObjectCache() for the current default and note that this setting is separate from the max main memory parameter. 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 data textures on the GPU, for example, changing the data range (
SoDataRange). We recommend setting this variable to false unless the memory conserving feature for compressed tiles is critical.
When the data set's texturePrecision is at least equal to the numSignificantBits and you are not combining multiple data sets, i.e. your volume data is not under an
SoMultiDataSeparator, then the data range scaling can be applied on the fly during rendering (i.e. on the GPU). This implies that data textures don't need to be regenerated when the data range changes and interactivity is much better.
This parameter doesn't actually resend data to the GPU but it does require updating the sub-tile min/max values, which can be quite costly. Setting subDivideTiles to false may increase DataRange performance (the default is false).
dataRangeId 1 min 0 max 0 mapOnFullColorRange true
Fields Modifier and Type Field Description
dataRangeIdThis field allows the use of multiple data ranges for the same shape.
mapOnFullColorRangeSpecifies how to map data values that are outside of the data range.
maxMaximum data value of the data range.
minMinimum data value of the data range.
Constructors Constructor Description
Methods inherited from class com.openinventor.inventor.nodes.SoNode
affectsState, callback, copy, copy, distribute, doAction, getAlternateRep, getBoundingBox, getByName, getMatrix, getPrimitiveCount, getRenderEngineMode, getRenderUnitID, GLRender, GLRenderBelowPath, GLRenderInPath, GLRenderOffPath, grabEventsCleanup, grabEventsSetup, handleEvent, isBoundingBoxIgnoring, isOverride, pick, rayPick, search, setOverride, touch, write
Methods inherited from class com.openinventor.inventor.fields.SoFieldContainer
copyFieldValues, copyFieldValues, enableNotify, fieldsAreEqual, get, getAllFields, getEventIn, getEventOut, getField, getFieldName, hasDefaultValues, isNotifyEnabled, set, setToDefaults
Methods inherited from class com.openinventor.inventor.misc.SoBase
dispose, getName, isDisposable, isSynchronizable, setName, setSynchronizable
public final SoSFInt32 dataRangeIdThis field allows the use of multiple data ranges for the same shape. By default all data range nodes are initialized to a data range id of 1. If you want to use multiple data ranges, different data range ids must be assigned. The data range id is only used in a render compositing scheme (see
- Open Inventor 6.1.2
public final SoSFDouble min
public final SoSFDouble maxMaximum data value of the data range.
public final SoSFBool mapOnFullColorRangeSpecifies how to map data values that are outside of the data range. If mapOnFullColorRange is true (default), then any data values less than or equal to the
mindata value are mapped to the first color entry and any data values greater than or equal to the
maxdata value are mapped to the last color entry.
If mapOnFullColorRange is false, then any data value less than
mindata value is mapped to the first color entry and the
mindata value is mapped to the second color entry; any data value greater than the
maxdata value is mapped to the last color entry and the
maxdata value is mapped to the next to the last color entry.