TET_MESH_TET_NEIGHBORS
Interactive Program for
Tet Mesh Neighbors

TET_MESH_TET_NEIGHBORS is a FORTRAN90 program which reads information defining a tet mesh of points in 3D, and determines, for each face of each tetrahedron, the index of the neighboring tetrahedron that shares that face.

The tet mesh is defined by a node file containing the coordinates of nodes, and a tetra file containing sets of 4 or 10 node indices. For this calculation, though, only the tetra file is needed.

If a tetrahedron is on the boundary, then one or more of its faces will not be shared by any tetrahedron. Such cases will be indicated by specifying the corresponding neighbor value as -1.

Usage:

tet_mesh_tet_neighbors tetra_file.txt

reads the tetrahedral part of a tet mesh definition, computes the neighbors, and writes them out as tetra_file.neighbors.txt.

Related Programs:

GEOMPACK is a FORTRAN90 library which contains a routine DTRIS3 that can compute the tet mesh for a set of 3D points, as well as the adjacency information.

MATLAB has a command delaunay3 that can compute the tet mesh for a set of 3D points.

NEIGHBORS_TO_METIS_GRAPH is an executable FORTRAN90 program which reads a tet mesh neighbor file created by TET_MESH_TET_NEIGHBORS and writes a modified version of the same data suitable for input to the mesh partitioning program METIS.

TABLE_TET_MESH is an executable FORTRAN90 program which can compute the tet mesh for a given set of points.

TEST_TET_MESH is a FORTRAN90 library defining a few test regions for the generation of a tet mesh.

TET_MESH is a FORTRAN90 library of routines useful for work with tet meshes.

TET_MESH_DISPLAY is a MATLAB program which can read in the node and tetra files defining a tet mesh and display a wireframe image.

TET_MESH_DISPLAY_OPEN_GL is a C++ executable program which reads a tet mesh and displays the nodes and edges using OpenGL.

TET_MESH_L2Q is an executable FORTRAN90 program which can convert a linear (4-node) tet mesh to a quadratic (10-node) tet mesh.

TET_MESH_ORDER4 is a directory which contains a description and examples of a tet mesh using order 4 elements.

TET_MESH_ORDER10 is a directory which contains a description and examples of a tet mesh using order 10 elements.

TET_MESH_Q2L is an executable FORTRAN90 program which can convert a quadratic (10-node) tet mesh to a linear (4-node) tet mesh.

TET_MESH_QUALITY is an executable FORTRAN90 program which can compute the quality of a tet mesh.

TET_MESH_RCM is an executable FORTRAN90 program which takes a tet mesh and relabels the nodes to reduce the bandwidth of the corresponding adjacency matrix.

TET_MESH_REFINE is an executable FORTRAN90 program which can refine a tet mesh.

TET_MESH_TET_NEIGHBORS is available in a C++ version and a FORTRAN90 version and a MATLAB version.

TET_MESH_TET_NEIGHBORS is a data directory containing a description and examples of the format for storing information about neighboring tetrahedrons in a tetrahedral mesh.

Reference:

1. Herbert Edelsbrunner,
   Geometry and Topology for Mesh Generation,
   Cambridge, 2001,
   ISBN: 0-521-79309-2,
   LC: QA377.E36.
2. Barry Joe,
   GEOMPACK - a software package for the generation of meshes using geometric algorithms,
   Advances in Engineering Software,
   Volume 13, 1991, pages 325-331.
3. Per-Olof Persson, Gilbert Strang,
   A Simple Mesh Generator in MATLAB,
   SIAM Review,
   Volume 46, Number 2, June 2004, pages 329-345.

Source code

• tet_mesh_tet_neighbors.f90, the source code.
• tet_mesh_tet_neighbors.csh, commands to compile, link and load the source code.

Examples and Tests

CUBE is a simple example of 8 nodes in a cube. Test files you may copy include:

• cube_nodes.txt, the node file.
• cube_tetras.txt, the tetrahedron file.
• cube_tetras.neighbors.txt, the neighbor information computed by the program.
• cube_output.txt, the printed output from the program.

List of Routines

• MAIN is the main program for TET_MESH_TET_NEIGHBORS.
• CH_CAP capitalizes a single character.
• CH_EQI is a case insensitive comparison of two characters for equality.
• CH_TO_DIGIT returns the integer value of a base 10 digit.
• DTABLE_DATA_READ reads data from a double precision table file.
• DTABLE_HEADER_READ reads the header from a double precision table file.
• FILE_COLUMN_COUNT counts the number of columns in the first line of a file.
• FILE_NAME_EXT_GET determines the "extension" of a file name.
• FILE_NAME_EXT_SWAP replaces the current "extension" of a file name.
• FILE_ROW_COUNT counts the number of row records in a file.
• GET_UNIT returns a free FORTRAN unit number.
• I4COL_COMPARE compares columns I and J of an I4COL.
• I4COL_SORT_A ascending sorts an I4COL of columns.
• I4COL_SWAP swaps columns J1 and J2 of a integer array of column data.
• I4I4I4_SORT_A ascending sorts a triple of I4's.
• I4MAT_TRANSPOSE_PRINT prints an I4MAT, transposed.
• I4MAT_TRANSPOSE_PRINT_SOME prints some of the transpose of an I4MAT.
• ITABLE_DATA_READ reads data from an integer table file.
• ITABLE_DATA_WRITE writes data to an integer table file.
• ITABLE_HEADER_READ reads the header from an integer table file.
• ITABLE_HEADER_WRITE writes the header to an integer table file.
• ITABLE_WRITE writes an ITABLE file.
• R8MAT_TRANSPOSE_PRINT prints an R8MAT, transposed.
• R8MAT_TRANSPOSE_PRINT_SOME prints some of an R8MAT, transposed.
• S_BLANK_DELETE removes blanks from a string, left justifying the remainder.
• S_INDEX_LAST_C finds the LAST occurrence of a given character.
• S_TO_I4 reads an I4 from a string.
• S_TO_I4VEC reads an I4VEC from a string.
• S_TO_R8 reads an R8 from a string.
• S_TO_R8VEC reads an R8VEC from a string.
• S_WORD_COUNT counts the number of "words" in a string.
• SORT_HEAP_EXTERNAL externally sorts a list of items into ascending order.
• TET_MESH_NEIGHBOR_TETS determines tetrahedron neighbors.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TIMESTRING writes the current YMDHMS date into a string.

You can go up one level to the FORTRAN90 source codes.