ylPropagateAlongField
    ---------------------

Propagate regions down a vector field

From all voxels of the seed volume that have the target label, the field
is followed in fixed-size steps until a seed is reached, or the maximum
number of iterations is exceeded.

Options :

--seeds <string>
    volume of labels (either S16 or S32):
    - positive labels are seeds,
    - zero is the region of propagation,
    - negative labels are forbidden regions.

[ --grad-field <file name (read only): VolumeRef of FLOAT> ]
    scalar field whose gradient is to be advected along

[ --fieldx <file name (read only): VolumeRef of FLOAT> ]
    x component of vector field to advect along

[ --fieldy <file name (read only): VolumeRef of FLOAT> ]
    y component of vector field to advect along

[ --fieldz <file name (read only): VolumeRef of FLOAT> ]
    z component of vector field to advect along

[ --target-label <S32> ]
    voxels having this label are used as starting points [default: 0]

[ --step <FLOAT> ]
    size of the advection step (millimetres) [default: 0.03]

[ --max-iter <U32> ]
    abort after so many iterations [default: 1000]

--output <string>
    output the propagated regions

[ --dest-points <filename: VolumeRef of FLOAT> ]
    output the destination points for each propagated voxel

[ --output_4d_volumes <S32> ]
    Write 4D images as several 3D files (0 = series of 3D volumes, 1 = one 4D
    volume, no value = use .aimsrc configuration files)

[ --debugLevel <S32> ]
    Set debug information level (default = 0)

[ --verbose [ <S32> ] ]
    Set verbosity level (default = 0, without value = 1)

[ -h | --help <boolean> ]
    show help message

[ --version <boolean> ]
    show Cartograph version

[ --info <boolean> ]
    show libraries information (install, plugins, paths, etc.)

[ --optionsfile <string> ]
    Read additional commandline options from the specified file (one switch or
    value per line)