This is the abstract base class for classes that convert existing data sets into the LDM (Large Data Management) format.

SoConverter provides powerful features including:

• Command line parsing for easy creation of stand-alone converter programs.

• Checkpoint and restart for interrupted conversions.

• Multiple subsampling algorithms for creating low resolution tiles.

• Automatic loading of any supported data format (see SoVolumeData).

• Conversion of any data format by providing a custom reader (see SoVolumeReader).

• Special handling to minimize disk space for "thin volumes" where one dimension is smaller than the tile size. (Currently only implemented for Z dimension.)

• Optional data compression to reduce disk space.

• Optional data type conversion, e.g. float to byte.

Information common to all converter classes is included here including command line, incomplete conversion, compression and subsampling. Normally you will use, for example, the derived class SoVolumeConverter to convert volume data. You can also subclass from SoVolumeConverter to use a custom volume reader, provide a custom subsampling method, etc.

Command Line

When used as a command line application the string should have the following form:

inputFilename [-t tiledim] [-o filename] [-O [filename]] [-m memsize] [-h] [-w B|L] [-f u8|u16|u32|s8|s16|s32|f [-r min max]] [-q] [-D] [-P portnum] [-c type] [-l level] [-C] [-s [0..N]] [-u value] [-verticalFlip]

where:

-t tiledim	Dimension of tiles. Must be a power of two. Default is 64, meaning 64x64x64.
-b bordersize	DEPRECATED Since OIV9.0, this parameter will be ignored.
-o filename	Name of created XML header ldm file. Default is inputFilename with extension .ldm.
-O filename	Name of the file containing the data. If filename is omitted, the default filename is the same as the output filename specified by the -o option, with extension .dat instead.
-m memsize	Maximum size of memory to use in MB. Default is 512 MB.
-h	Output the header only.
-w wordfmt	Indicates the target machine word format is Big Endian (B) or Little Endian (L). Default is the current machine word format.
-f datafmt	Indicates the output data format with * = 8,16,32. u*:unsigned integer, s*:signed integer, f:float. If the output data format is float, the values are mapped to the range [0-1]. Default is the input data format.
-r min max	Indicates the input data range to map to the new data format specified by the -f option. If not specified, and input type is float and ouput type is integer, the values are simply cast into the output data type.
-q	Quiet mode.
-c type	Type of compression used. See also "-l level". By default the following compression types are available:	gzip: This is a lossless compression and can be used on any type of data. See SoGzipDataCompressor.	jpeg: This is a lossy compression. See SoJpegDataCompressor. Limitation: Can only be used on 8-bit scalar data sets.	jp3d: This is a wavelet compression that can be lossless or lossy. See SoJp3dDataCompressor. Limitation: 32 bit data values (float or integer) are always converted to 16 bit values.
-l level	Level of compression used. See also "-c type". The meaning of this parameter depends on the type of compression used: - gzip: <BR> Lossless compression. Level must be between 0 and 9: 0 gives no compression, 9 gives best compression but slower speed. Default is 3. - jpeg: <BR> Lossy compression. Level must be between 0 and 100: 0 gives best compression but most loss of data, 100 gives minimum compression and minimum data alteration. Default is 85. - jp3d: <BR> Wavelet compression that can be lossless or lossy. A level of 0 specifies the lossless mode, and any other value sets the target PSNR (Peak Signal to Noise Ratio). Typical values for PSNR are: 70dB for near lossless mode, and 40dB for visually lossless mode.
-C	Data integrity check. When compression is enabled using -c, adds a data integrity check value to all compressed tiles. If the environment variable LDM_COMPRESS_CHECK_CRC32 is set, data values will be checked each time they are read from disk.
-s 0..n	Specifies the algorithm used to build low resolution tiles. Available options are :	0 to use decimation algorithm (one voxel out of two).	n to use weighted average algorithm : voxels of tile of resolution N+1 are built from the average of the 6 neighbors from resolution N and the current voxel value weighted by n. If not specified, by default the decimation algorithm is used (n=0).
-u value	Undefined value. The given value will marked as undefined in the LDM file. This is currently used by SoHeightFieldRender (vertices with undefined values are not rendered).
-rgba	Specifies that output will be unsigned int32 RGBA values.
-noHistogram	Disable histogram computation (conversion will be faster).
-B value	Define threshold value to generate a bitset dataset. Any value in the dataset less than or equal to the threshold will generate a zero bit. Values greater than threshold will generate a one bit.
-verticalFlip	Flip the output on Y axis.

The return value may be one of the following:

<TABLE border=1 cellspacing=0 cellpadding=5>
  <TR><TD valign=_top> CVT_NO_ERROR                  <TD valign=_top> No problem, task complete
  <TR><TD valign=_top> CVT_INPUT_PARAMS_PROBLEM      <TD valign=_top> Input parameters problem: input filename missing, bad parameter

CVT_FILE_EXT_UNKNOWN

Unknown file type (file extension)

CVT_CANT_OPEN_INPUT_FILE

Could not open input file (does not exist)

CVT_CANT_CREATE_DATA_FILE

Could not create data file

CVT_CANT_CREATE_HEADER_FILE

Could not create header file

CVT_NOT_ENOUGH_DISK_SPACE

Could not allocate disk space for the data file

CVT_ABORTED

Conversion has been aborted by the application, task not complete

CVT_NO_NODE

Distributed converter cannot be used as the license does not allow any client node

CVT_NO_LDM_LICENSE

No LDM license

Incomplete Conversion

The converter saves the progress of the conversion in case the user wishes to abort or start visualizing the converted data or if the program crashes for any reason. In this case, the LDM files (header and data) are coupled with a completion file (name of the header file with an extension of .fcp). When restarting the converter, if the header file points to a .fcp file (XML tag <completionFilename>), the conversion will restart where it previously ended. When visualizing an incompletely converted file, it is possible to know where data actually exists by turning on the topology outlines (see SoVolumeRendering). Red outlines indicate actual data.

In order to restart an incomplete conversion, the header file must be in synch with the completion file. For this reason when writing the pair of header/completion files, the converter first backs up the pair of files before overwriting them (.ldm and .fcp with .bck extension). If the header file is lost or its size is less than the size of the backed up header file, then you can rename the backed up completion and header files to restart the conversion.

EXAMPLE

A basic command line converter program would look like this:

public class CommandLine
{
 public static void Main(string[] args)
 {
   // Create parameter object from command line args
   SoConverterParameters parameters = 
       SoConverterParameters.Create(args.Length, args);

   // Start converter 
   SoVolumeConverter converter = new SoVolumeConverter();
   int result = converter.Convert( parameters );
 }
}

EXAMPLE

You can also invoke the converter from an application by creating an instance of SoConverterParameters and setting the desired parameters. For example to convert an input file (in a format supported by VolumeViz) to LDM format with compression enabled:

SoConverterParameters parameters = new SoConverterParameters();
parameters.SetInputFileName( "filename.sgy" );
parameters.SetTileDim( 128 );

SoVolumeConverter converter = new SoVolumeConverter();
int result = converter.Convert( parameters );

Reference