TRIANGULATION_DISPLAY
Plot a Triangulation

TRIANGULATION_DISPLAY is a MATLAB program which plots a triangulation.

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

If a third file is available, listing the element neighbors of each element, then the program will read that file, and can display that information as well.

Usage:

triangulation_display ( 'prefix', node_vis, element_vis, (neighbor_vis) )

• 'prefix'_nodes.txt, the node coordinate file;
• 'prefix'_elements.txt, the element node file;
• 'prefix'_element_neighbors.txt, the optional element neighbor file;

• 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.

• 0, do not show the element neighbor labels;
• 1, show the element neighbor labels;

Licensing:

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

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;

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

TRIANGLE_DISPLAY, a MATLAB program which displays the nodes and elements of a triangulation on the MATLAB graphics screen, assuming the data has been stored in NODE and ELE files by the TRIANGLE program.

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:

• triangulation_display.m the source code.

Examples and Tests:

BOX4 is an order 4 triangulation.

• box4_nodes.txt, the nodes.
• box4_nodes.png, an image of the nodes.
• box4_elements.txt, the elements.
• box4_elements.png, an image of the elements.
• box4_element_neighbors.txt, the element neighbors.
• box4_element_neighbors.png, an image of the element neighbors.

CIRCLE is a circular region, triangulated using order 3 elements.

• circle_nodes.txt the point coordinates.
• circle_nodes.png an image of the elements.
• circle_elements.txt the elements
• circle_elements.png an image of the elements.

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

• elbow3_nodes.txt the point coordinates.
• elbow3_nodes.png an image of the nodes.
• elbow3_elements.txt the elements.
• elbow3_elements.png an image of the elements.

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

• ell3_nodes.txt, the nodes.
• ell3_nodes.png, an image of the nodes.
• ell3_elements.txt, the elements.
• ell3_elements.png, an image of the elements.
• ell3_element_neighbors.txt, the element neighbor array.
• ell3_element_neighbors.png, an image of the element neighbor labels.

GREENLAND is a triangulation of Greenland, using 33,343 nodes and 64,125 elements of order 3 elements. The image is too dense to display in full, so MATLAB's "zoom" facility was used to display a small portion of the mesh.

• greenland_nodes.txt, the nodes.
• greenland_elements.txt, the elements.
• greenland_elements.png, an image of the elements, after "zooming in" twice.

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 elements.
• hex_holes3_elements.png, an image of the elements.

IRREG6 is an order 6 triangulation.

• irreg6_nodes.txt, the nodes.
• irreg6_elements.txt, the elements.
• irreg6_elements.png, an image of the elements.

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 elements;
• lake3_elements.png, an image of the elements.

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