triangulation_mask, a Fortran90 code which reads the nodes and triangles that define a triangulation, calls a user routine which determines whether each triangle is to be preserved or discarded ("masked") from the triangulation, and writes out new node and triangle files that define the masked triangulation.
The input file prefix_nodes.txt contains the node information for the triangulation. Each data line contains the X and Y coordinates of a single node.
The input file prefix_elements.txt contains the triangle information for the triangulation. Each line contains the indices of 3 or 6 nodes that form a triangle.
One motivation for creating this code is as follows. Suppose we have a set of points that lie on the boundary or inside of a non-convex region. If we naively call an unconstrained Delaunay triangulation routine, such as TABLE_DELAUNAY, then because the region is not convex, it is possible to create triangles which lie outside the region.
An easy way to correct this problem is to call a user routine and pass it the indices and coordinates of each triangle. The user can then decide to drop any triangle whose centroid, say, lies outside the region.
Other masking criteria might drop triangles that are too small, or that have too small an angle, or that lie inside some interior hole. These choices are entirely up to the user.
The user masking subroutine has the form:
subroutine triangle_mask ( dim_num, triangle_order, nodes, coord, mask )with arguments:
The user masking routine must be compiled and linked with the software, perhaps with a command like:
F90 triangulation_mask.o triangle_mask.f90We will assume that the executable is renamed to triangulation_mask.
The code is the executed with a command like:
triangulation_mask prefixwhere prefix is the common filename prefix:
The information on this web page is distributed under the MIT license.
triangulation_mask is available in a C++ version and a Fortran90 version and a MATLAB version and an Octave version.
table_delaunay, a Fortran90 code which can compute the Delaunay triangulation of a set of points.
triangle, a C code which computes a triangulation of a geometric region.
triangulation, a Fortran90 code which carries out various operations on order 3 (linear) or order 6 (quadratic) triangulations.
triangulation_boundary_nodes, a Fortran90 code which reads data defining a triangulation, determines which nodes lie on the boundary, and writes their coordinates to a file.
triangulation_corner, a Fortran90 code which patches triangulations so that no triangle has two sides on the boundary.
triangulation_delaunay_discrepancy, a Fortran90 code which measures the amount by which a triangulation fails the local Delaunay test;
triangulation_display_opengl, a C++ code which reads files defining a triangulation and displays an image using Open GL.
triangulation_histogram, a Fortran90 code which computes histograms of data over a triangulation.
triangulation_l2q, a Fortran90 code which reads data defining a 3-node triangulation and generates midside nodes and writes out the corresponding 6-node triangulation.
triangulation_orient, a Fortran90 code which reads data defining a triangulation and reorients those triangles that have negative orientation.
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_plot, a Fortran90 code which reads data defining a triangulation and creates a PostScript image of the nodes and triangles.
triangulation_q2l, a Fortran90 code which reads data defining a 6-node triangulation, and subdivides each triangle into 4 3-node triangles, writing the resulting triangulation to a file.
triangulation_quad, a Fortran90 code which estimates the integral of a function over a triangulated region.
triangulation_quality, a Fortran90 code which reads data defining a triangulation and computes a number of quality measures.
triangulation_rcm, a Fortran90 code which reads data defining a triangulation, determines an ordering of the nodes that will reduce the bandwidth of the adjacency matrix, and writes the new triangulation information to a file.
triangulation_refine, a Fortran90 code which reads data defining a triangulation, replaces each triangle by four congruent smaller ones, and writes the new triangulation information to a file.
triangulation_triangle_neighbors, a Fortran90 code which reads data defining a triangulation, determines the neighboring triangles of each triangle, and writes that information to a file.