functions in hex.i - b

    nlist = bi_dir(tracker, mesh, rays, slimits, c, s)  


Perform hexX_track and track_reduce on a ray that enters  
the problem at the given point on the ray.  This requires  
tracking the ray in both directions from the given point,  
hence this function name indicating bi-directional tracking.  
This is unnecessary when the entry point search was over  
the problem boundary, or when the SLIMITS for the rays  
always lie in one direction relative to the starting point.  
TRACKER is the function used to track the rays, normally  
  one of hex5_track, hex_24f_track, or hex24b_track.  
MESH is the problem mesh returned by hex_mesh or hydra_mesh;  
  it should be generated using the entry option that finds  
  the cell containing the given point on the ray.  
RAYS is the 3-by-nrays-by-2 array of rays, as for hex5_track  
SLIMITS is nil or the ray tracking limits as for track_reduce  
C, S, together with NLIST are the output arrays, as for  
  track_reduce  
Interpreted function, defined at i0/hex.i   line 226