section h of routines in hex.i

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# functions in hex.i - h

 hex24b_track ``` hex24b_track builtin function, documented at i0/hex.i line 38 ``` SEE hex5_track

 hex24f_track ``` hex24f_track builtin function, documented at i0/hex.i line 38 ``` SEE hex5_track

 hex5_track ``` c= hex5_track(mesh, rays, s) c= hex24f_track(mesh, rays, s) c= hex24b_track(mesh, rays, s) track 3 x Nrays x 2 RAYS through the 3D MESH. RAYS(,,1) are points on the rays, while RAYS(,,2) are normalized ray directions. The c return value and the S parameter are a long and double array respectively, with number of elements equal to the total number of intersections of all the RAYS with faces of the MESH, plus one for any RAY which misses MESH entirely. The values of c are: [#hits,cell1,cell2,cell3,..., #hits,cell1,cell2,cell3,..., ...] where each #hits is followed by the list of cell indices (assuming i=1, j=1, and k=1 are present but meaningless in cell arrays -- that is, assuming zone centered arrays have the same dimensions as XYZ rather than one less in each direction). Rays which miss the mesh entirely have #hits=1, all others have #hits>=2 since they must exit. #hits<0 means a ray reentered the mesh for abs(#hits) more face crossings, but this currently cannot happen. The values of S correspond to c: [s0,s1,s2,s3,..., s0,s1,s2,s3,..., ...] which are the distances along the ray measured from RAYS(,,1) in the direction of RAYS(,,2) where the ray pierces a cell face. For rays which miss the mesh, the value of s0 is a diagnostic telling why they missed (see compiled code). Function hex5_track uses the 5-tet decomposition for hexes, which is not unique when the quad faces are non-planar. You may be able to get an idea of this effect by setting hex_triang the opposite way and redoing the trace. Functions hex24f_track and hex24b_track use the face and body centered 24-tet decompositions for hexes. These are unique; however, hex_triang may in rare cases change the trace slightly, since the entry search algorithm still involves triangulating the surface quads. builtin function, documented at i0/hex.i line 38 ``` SEE ALSO: hydra_mesh,   hex_triang,   reg_track,   track_reduce,   c_adjust,   pic3_rays,   conv3_rays

 hex_mesh ``` mesh= hex_mesh(xyz, bound, nbnds, &mbnds, nblk, &blks, start) create a 3D mesh object from the multiblock mesh parameters XYZ is NBLK 3 x Ni x Nj x Nk coordinate arrays packed together BOUND is NBLK 3 x Ni x Nj x Nk face boundary markers packed NBNDS is length of MBNDS MBNDS is HX_blkbnd describing each internal block boundary face NBLK is number of blocks BLKS is NBLK HX_block objects describing the block structure START is 0-origin 6*cell+face index of first boundary face/cell or -1-cell to trace from centroid of that cell to point p on ray to begin tracking builtin function, documented at i0/hex.i line 10 ``` SEE ALSO: hex5_track,   hydra_mesh,   hex_startflag

 hex_mesh2 ``` mesh= hex_mesh2(xyz, bounds) old interface for hex_mesh create a 3D mesh object from the 3 x Ni x Nj x Nk coordinate array XYZ and the list of 6 BOUNDS: BOUNDS(1), BOUNDS(2) for the i=1,Ni boundaries BOUNDS(3), BOUNDS(4) for the j=1,Nj boundaries BOUNDS(5), BOUNDS(6) for the k=1,Nk boundaries The BOUNDS values are: 1 if this is a problem boundary 2 if this is a reflecting boundary 3 if this is a periodic boundary interpreted function, defined at i0/hex.i line 596 ``` SEE ALSO: hydra_mesh

 hex_query ``` start= hex_query(mesh, xyz, bound, mbnds, blks) query a mesh created by hex_mesh, returning the arrays passed to that function (these are not copies -- be careful not to clobber them) function return value is the start index builtin function, documented at i0/hex.i line 27 ``` SEE ALSO: hex5_track,   hydra_mesh

 hex_startflag ``` old_flag= hex_startflag(new_flag) possibly set flag to NEW_FLAG, always return OLD_FLAG, where flag value is 0 (default) to begin search for new entry point at previous entry point, 1 to begin search for new entry point from mesh start face for every ray. Any other value of NEW_FLAG returns OLD_FLAG without changing it. builtin function, documented at i0/hex.i line 489 ``` SEE ALSO: hex_mesh

 hex_triang ``` old_flag= hex_triang(new_flag) possibly set flag to NEW_FLAG, always return OLD_FLAG, where flag value is 0 for default mesh triangulation, 1 for opposite triangulation, and 2 on input to signal not to change the current value. The triangulation value can affect the result of hex5_track if the quad faces of the mesh are not planar. builtin function, documented at i0/hex.i line 474 ``` SEE ALSO: hex5_track

 hydra_adj ``` hydra_adj builtin function, documented at i0/hex.i line 534 ```

 hydra_blks ``` hydra_blks builtin function, documented at i0/hex.i line 515 ```

 hydra_bnd ``` hydra_bnd builtin function, documented at i0/hex.i line 520 ```

 hydra_mesh ``` mesh= hydra_mesh(f) or mesh= hydra_mesh(f, ublk, i0, j0, k0, face) or mesh= hydra_mesh(f, ublk, i0, j0, k0) read a 3D mesh object from the hydra PDB/Silo file F. Note that the boundary arrays are adjusted to the hex convention that cells with i=1, j=1, k=1 are missing, rather than the hydra convention that i=imax, j=jmax, k=kmax are missing. In the first form, the ray entry search will start on the first open boundary face in the mesh. If the actual problem boundary is not convex, you need to identify a surface of constant i, j, or k in the problem which is convex, and which all the rays you intend to trace intersect. UBLK is the user block number (starting from 0), I0, J0, K0 are the (1-origin) logical coordinates of a hydra *cell*. Note that unlike hex cells, the hydra cell bounded by nodes (1,1,1) and (2,2,2) is numbered (1,1,1). (Hex numbers it (2,2,2).) FACE is the face number on cell (I0,J0,K0) which you want a ray to enter. 0 means the -I face, 1 the +I face, 2 the -J face, 3 the +J face, 4 the -K face, and 5 the +K face. As you step from this cell to its neighbors, then to their neighbors, and so on, this face must trace out a convex surface for the ray entry search. Rays not intersecting this surface will not enter the problem; the ray trace will begin at this surface, not at -infinity. If FACE==-1 or is omitted (as in the third form), then the given points on the rays are assumed to lie inside the mesh, and a pseudo ray from the centroid of cell (I0, J0, K0) will be tracked to the given point on each ray; the ray will be launched into the cell containing that point. interpreted function, defined at i0/hex.i line 542 ``` SEE ALSO: hex_query,   hex5_track,   hydra_data,   openh

 hydra_mrk ``` hydra_mrk builtin function, documented at i0/hex.i line 528 ```

 hydra_start ``` hydra_start, mesh, start change the starting cell of the hydra MESH (returned by hydra_mesh) to START. If called as a function, returns old start value. interpreted function, defined at i0/hex.i line 688 ``` SEE ALSO: hydra_mesh,   hydra_data