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TET_MESH_BOUNDARY\ Triangular Surface Formed by Tet Mesh Boundary {#tet_mesh_boundary-triangular-surface-formed-by-tet-mesh-boundary align=”center”} ==============================================

TET_MESH_BOUNDARY is a C++ program which reads information defining a tetrahedral mesh of points in 3D, and determines the triangular faces that form the boundary of the mesh; it writes out files containing the nodes and elements defining this “TRI_SURFACE”.

The tet mesh is defined by a node file containing the coordinates of nodes, and an element file containing sets of 4 or 10 node indices. (The present version of the program will only handle the 4 node case.)

Each tetrahedron has 4 triangular faces. Most of these faces will be shared by a neighbor tetrahedron, but those faces that are not shared by a neighbor constitute the boundary of the mesh.

The program identifies the triangular faces that form the boundary, and writes two files, a “boundary_node” file that lists the coordinates of the nodes, and a “boundary_element” file that lists the indices of the nodes used to form the faces. This pair of files defines a triangulated 3D surface, or “TRI_SURFACE”.

Usage: {#usage align=”center”}

tet_mesh_boundary prefix

where prefix is the common file prefix:

prefix_nodes.txt, the node coordinates;
prefix_elements.txt, the element definitions;
prefix_boundary_node_mask.txt, is 0 for each interior node, 1 for each boundary node;
prefix_boundary_nodes.txt, the boundary node coordinates;
prefix_boundary_elements.txt, the boundary element definitions;

Licensing: {#licensing align=”center”}

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages: {#languages align=”center”}

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

TET_MESH, a C++ library which is useful for work with tet meshes.

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

TET_MESH_DISPLAY_OPENGL, a C++ program which reads a tet mesh and displays the nodes and edges using OpenGL.

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

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

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

TRI_SURFACE, a data directory which contains examples of TRI_SURFACE files, a 3D surface described by a collection of triangles.

TRI_SURFACE_DISPLAY, a MATLAB program which displays the 3D graphics information in a TRI_SURFACE file;

TRI_SURFACE_DISPLAY_OPENGL, a C++ program which displays the 3D graphics information in a TRI_SURFACE file using OpenGL.

Reference: {#reference align=”center”}

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

Source code {#source-code align=”center”}

tet_mesh_boundary.cpp, the source code.

Examples and Tests {#examples-and-tests align=”center”}

CUBE is a tetrahedral mesh of a cube.

cube_nodes.txt, the node file.
cube_elements.txt, the element file.
cube.png, an image of the tetrahedral mesh.
cube_boundary_node_mask.txt, the boundary node mask file.
cube_boundary_nodes.txt, the boundary node file.
cube_boundary_elements.txt, the boundary element file.
cube_output.txt, the printed output from the program.

P04 is a tetrahedral mesh of a sphere.

p04_nodes.txt, the node file.
p04_elements.txt, the element file.
p04.png, an image of the tetrahedral mesh.
p04_boundary_node_mask.txt, the boundary node mask file.
p04_boundary_nodes.txt, the boundary node file.
p04_boundary_elements.txt, the boundary element file.
p04_output.txt, the printed output from the program.

List of Routines {#list-of-routines align=”center”}

MAIN is the main program for TET_MESH_BOUNDARY.
CH_CAP capitalizes a single character.
CH_EQI is true if two characters are equal, disregarding case.
CH_TO_DIGIT returns the integer value of a base 10 digit.
FILE_COLUMN_COUNT counts the columns in the first line of a file.
FILE_ROW_COUNT counts the number of row records in a file.
I4_MAX returns the maximum of two I4’s.
I4_MIN returns the minimum of two I4’s.
I4COL_COMPARE compares columns I and J of an I4COL.
I4COL_SORT_A ascending sorts the columns of an I4COL.
I4COL_SWAP swaps two columns of an I4COL.
I4I4I4_SORT_A ascending sorts a triple of I4’s.
I4MAT_DATA_READ reads data from an I4MAT file.
I4MAT_HEADER_READ reads the header from an I4MAT file.
I4MAT_TRANSPOSE_PRINT_SOME prints some of an I4MAT, transposed.
I4MAT_WRITE writes an I4MAT file with no header.
I4VEC_CUM computes the cumulutive sum of the entries of an I4VEC.
I4VEC_SUM sums the entries of an I4VEC.
MESH_BASE_ZERO ensures that the element definition is zero-based.
R8MAT_DATA_READ reads the data from an R8MAT file.
R8MAT_HEADER_READ reads the header from an R8MAT file.
R8MAT_TRANSPOSE_PRINT_SOME prints some of an R8MAT, transposed.
R8MAT_WRITE writes an R8MAT file with no header.
S_LEN_TRIM returns the length of a string to the last nonblank.
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_BOUNDARY_COUNT counts boundary faces and nodes in a tet mesh.
TET_MESH_BOUNDARY_SET sets the boundary faces in a tet mesh.
TIMESTAMP prints the current YMDHMS date as a time stamp.

You can go up one level to the C++ source codes.

Last revised on 22 December 2010.