TRIANGLE_DISPLAY
Plot a Triangulation from TRIANGLE Files

TRIANGLE_DISPLAY, a MATLAB program which plots a triangulation using files associated with Jonathan Shewchuk's triangle() program.

TRIANGLE_DISPLAY reads the node and element files created by the TRIANGLE program, and displays the information. The user controls how "visible" the nodes and elements are; in particular, nodes can be suppressed, or displayed, or displayed and numbered, and the same is true for elements.

TRIANGLE_DISPLAY is essentially a version of TRIANGULATION_DISPLAY modified to read input files that use the TRIANGLE format.

Jonathan Shewchuk provides a program called showme(), which is able to show the same information, and to perform other interesting operations. However, there are at least three reasons why the TRIANGLE_DISPLAY program is useful:

• the user is free to zoom interactively into any part of the mesh displayed by TRIANGLE_DISPLAY;
• the user can save the image (or the portion that has been zoomed) into a wide variety of graphic formats, include JPEG, PNG and TIFF, while showme() is restriced to PS and EPS formats; moreover if showme() tries to save a snapshot of a large file (such as "greenland"), it can take 20 minutes (after which I gave up) and a huge amount of space. The same image was generated in 20 seconds with this program, and a zoomed image saved to a small 50K file very quickly.
• it is fairly easy to modify the text of TRIANGLE_DISPLAY() to better suit the user's needs; in particular, it is easy to read in node-based data and produce contour plots (although I don't have any data to work with yet.)

Usage:

triangle_display ( 'prefix', node_vis, element_vis )

• 'prefix'.node, the node coordinates.
• 'prefix'.ele, the elements

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

• 0, do not show the elements;
• 1, show the elements;
• 2, show the elements and color them.
• 3, show the elements and color them, and label them.

Licensing:

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

Languages:

TRIANGLE_DISPLAY is available in a MATLAB version.

Related Data and Programs:

FEM_BASIS_T3_DISPLAY, a MATLAB program which displays a basis function associated with a linear triangle ("T3") mesh.

FEM_BASIS_T6_DISPLAY, a MATLAB program which reads a quadratic triangle mesh and displays any associated basis function.

GRIDLINES, a MATLAB library which gives the user more control over drawing gridlines on a graph than the builtin "grid on" command.

MESH_DISPLAY, a MATLAB program which reads data defining a polygonal mesh and displays it, with optional numbering.

MPAS_GRID_DISPLAY, MATLAB programs which can read an MPAS NETCDF grid file and display the primary polygonal mesh or the dual triangular mesh.

PLY_DISPLAY, a MATLAB program which displays an image of a 3D graphics file in PLY format;

SHOWME, a C program which uses the X Window library to display triangulatons, by Jonathan Shewchuk.

TRI_SURFACE_DISPLAY, a MATLAB program which reads data defining a triangular mesh of a 3D surface and displays it.

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

triangle_display_test

TRIANGLE_FILES, a data directory of examples of files used by the triangle and showme programs.

TRIANGLE_IO, a MATLAB library which can read or write some of the files created by Jonathan Shewchuk's triangle() program.

TRIANGULATION_DISPLAY, a MATLAB program which reads files defining a triangulation and displays an image.

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

TRIANGULATION_PLOT, a MATLAB program which plots a triangulation as a PostScript file.

Reference:

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:

• triangle_display.m the source code.
• timestamp.m prints the current YMDHMS date as a time stamp.