jburkardt

TRIANGULATION_PLOT\ Plot a Triangulation {#triangulation_plot-plot-a-triangulation align=”center”} ====================

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TRIANGULATION_PLOT is a C++ program which plots a triangulation.

TRIANGULATION_PLOT reads one file listing the nodes, and a second file consisting of groups of 3 or 6 nodes that make up triangles, and creates an Encapsulated PostScript image of the triangulation.

Usage: {#usage align=”center”}

triangulation_plot prefix node_vis triangle_vis

where prefix is the common prefix for the node and triangle files, and will also be used to name the output file:

• prefix_nodes.txt, the node coordinates (input);
• prefix_elements.txt, the triangulation (input);
• prefix.eps, the plot file (output);

and node_vis is an integer defining the node visibility:

• 0, do not show the nodes;
• 1, show the nodes;
• 2, show the nodes and label them.

and triangle_vis is an integer defining the triangle visibility:

• 0, do not show the triangles;
• 1, show the triangles;
• 2, show the triangles and label them.

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”}

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

Related Data and Programs: {#related-data-and-programs align=”center”}

TRIANGLE, a C program which computes a triangulation of a geometric region.

TRIANGULATION, a C++ library which is useful for working with triangulations.

TRIANGULATION_DISPLAY, a MATLAB program which displays the nodes and elements of a triangulation on the MATLAB graphics screen;

TRIANGULATION_DISPLAY_OPENGL, a C++ program which reads files defining a triangulation and displays an image using Open GL.

TRIANGULATION_NODE_TO_ELEMENT, a C++ program which reads files describing a set of nodes, their triangulation, and the value of one or more quantities at each node, and outputs a file that averages the quantities for each element. This operation in effect creates an “order1” finite element model of the data.

TRIANGULATION_ORDER3, a directory which contains a description and examples of order 3 triangulations.

TRIANGULATION_ORDER6, a directory which contains a description and examples of order 6 triangulations.

TRIANGULATION_SVG, a C++ program which creates an SVG image of a triangulation, which can be displayed by a web browser.

Reference: {#reference align=”center”}

1. Marc deBerg, Marc Krevald, Mark Overmars, Otfried Schwarzkopf,\ Computational Geometry,\ Springer, 2000,\ ISBN: 3-540-65620-0,\ LC: QA448.D38.C65.
2. Joseph ORourke,\ Computational Geometry,\ Second Edition,\ Cambridge, 1998,\ ISBN: 0521649765,\ LC: QA448.D38.

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

• triangulation_plot.cpp, the source code.

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

ELBOW3 is an elbow-shaped region, triangulated using order 3 triangles.

• elbow3_nodes.txt the point coordinates.
• elbow3_elements.txt the triangulation.
• elbow3_triangulation.png is a PNG image of the triangulation.

ELL3 is an order 3 triangulation of a set of nodes in an L-shaped region.

• ell3_nodes.txt, the nodes.
• ell3_elements.txt, the triangulation.
• ell3_triangulation.png, a PNG image of the triangulation.

ELL6 is an order 6 triangulation of a set of nodes in an L-shaped region.

• ell6_nodes.txt, the nodes.
• ell6_elements.txt, the triangulation.
• ell6_triangulation.png, a PNG image of the triangulation.

HEX_HOLES3 puts a set of nodes into the double hexagonal hole region using CVT techniques, and creates an order 3 triangulation using TABLE_DELAUNAY.

• hex_holes3_nodes.txt, the nodes.
• hex_holes3_elements.txt, the triangulation.
• hex_holes3_triangulation.png, a PNG image of the triangulation.

LAKE3 uses constrained CVT methods to place nodes inside and on the boundary of the problem 14 triangulation region, a lake with an island. An order 3 triangulation is used.

• lake3_nodes.txt, the nodes;
• lake3_elements.txt, the triangles;
• lake3_triangulation.png, a PNG image of the triangulation.

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

• MAIN is the main program for TRIANGULATION_PLOT.
• 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_EXIST reports whether a file exists.
• FILE_ROW_COUNT counts the number of row records in a file.
• I4_MAX returns the maximum of two integers.
• I4_MIN returns the smaller of two integers.
• I4_MODP returns the nonnegative remainder of integer division.
• I4_WRAP forces an integer to lie between given limits by wrapping.
• 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.
• R8_HUGE returns a “huge” R8.
• R8_NINT returns the nearest integer to an R8.
• 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.
• 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.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TRIANGULATION_ORDER3_PLOT plots a 3-node triangulation.
• TRIANGULATION_ORDER4_PLOT plots a 4-node triangulation.
• TRIANGULATION_ORDER6_PLOT plots a 6-node triangulation.

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

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Last revised on 22 August 2009.