Class SoMultiDataSeparator

  • All Implemented Interfaces:

    public class SoMultiDataSeparator
    extends SoSeparator
    Separator for combining multiple data sets. The SoMultiDataSeparator node allows you to combine multiple data sets.

    This is the correct method for combining multiple data sets. Combining multiple data sets without inserting them under an SoMultiDataSeparator node may produce incorrect results and should be avoided.

    Each data set is represented by an SoDataSet node (typically an SoVolumeData node). Combining is enabled by an SoDataCompositor node for CPU combining or an SoVolumeShader node for GPU combining. A common use of GPU combining is to implement co-blending of multiple volumes, in other words using a fragment shader to combine the color and/or intensity values of the voxels.

    Some rules must be followed when doing render or data compositing:

    GPU combining must be implemented in a shader program written in the standard GLSL language. The shader program will be specified using an SoVolumeShader node. The shader source code is loaded using (for example) an SoFragmentShader object. Uniform parameters for the shader may be specified using the subclasses of SoShaderParameter. See SoVolumeShader for more information about the shader function library provided by VolumeViz.

    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.
    See SoVolumeShader for more details.

    For each data set there will typically be an SoDataRange node and an SoTransferFunction node to define the mapping from data values to color values. For each SoVolumeData a separate 3D texture will be generated and sent to the GPU. 3D textures can be generated with different precision (8-bit or 12-bit) according to the SoDataSet.texturePrecision field. The texture unit used for each data set is determined by the SoDataSet.dataSetId field. All colormaps are aggregated into a single 2D texture.

    A custom fragment shader can retrieve the voxel's data value from each 3D texture using the GLSL VolumeViz function:

     VVIZ_DATATYPE value = VVizGetData( dataSetId, texCoord );
    A custom fragment shader can lookup the color/intensity for each data value from the appropriate colormap, using the GLSL VolumeViz function:
     vec4 color = VVizTransferFunction( value, colorMapId );
    A custom fragment shader can then compute (using custom blending functions) the actual color for the voxel and output that color using the GLSL VolumeViz function:
     VVizOutputColor( color ):


    The following code shows how to do multidata rendering using an SoVolumeShader node to combine values for an SoVolumeRender node. Given two SoVolumeData nodes ds1 and ds2:

     SoVolumeShader volumeShader = new SoVolumeShader();
     SoVolumeData volumeData1 = new SoVolumeData();
     volumeData1.dataSetId.setValue( 0 );
     SoDataRange dataRange1 = new SoDataRange();
     dataRange1.dataRangeId.setValue( 0 );
     SoTransferFunction colorMap1 = new SoTransferFunction();
     SoVolumeData volumeData2 = new SoVolumeData();
     volumeData2.dataSetId.setValue( 1 );
     SoDataRange dataRange2 = new SoDataRange();
     dataRange2.dataRangeId.setValue( 1 );
     SoTransferFunction colorMap2 = new SoTransferFunction();
     SoVolumeRender volumeRender = new SoVolumeRender();
     SoMultiDataSeparator multiDataSep = new SoMultiDataSeparator();
         multiDataSep.addChild( volumeShader ); // Shader to combine volumes
         multiDataSep.addChild( volumeData1 );
         multiDataSep.addChild( dataRange1 );
         multiDataSep.addChild( colorMap1 );
         multiDataSep.addChild( volumeData2 );
         multiDataSep.addChild( dataRange2 );
         multiDataSep.addChild( colorMap2 );
         multiDataSep.addChild( volumeRender );

    See Also:
    SoDataSet, SoVolumeData, SoDataCompositor, SoVolumeShader
    • Constructor Detail

      • SoMultiDataSeparator

        public SoMultiDataSeparator()