functions in hex.i - r

    c= reg_track(x, y, z, rays, s)  


track RAYS through regular mesh defined by the 1D coordinate  
arrays X, Y, and Z.  Return values S and C are as for  
hex5_track, where the mesh is numberof(X) by numberof(Y) by  
numberof(Z).  
Builtin function, documented at i0/hex.i   line 85