SYNOPSIS:
    FIND_CLOSEST x y z dx dy dz targetset [sourceset]

DESCRIPTION:
    Fill the connected area starting at x,y,z. If no sourceset is
    given, or it is empty, use the class of the voxel at x/y/z.
    All voxels belonging to sourceset that are connected to x,y,z
    are remarked to targetset.
    The difference to FILLCONNECTED is, that it returns the coordinates
    of the found voxel which is closest to dx,dy,dz;

SEE ALSO:
    MARKCC_CONNECTED, FIND_COG
