TRIANGLE_GRID
Triangular Grid of Points

TRIANGLE_GRID is a FORTRAN77 library which generates a triangular grid of points.

Starting with any 3 points A, B, and C that define a triangle, we can divide each side of the triangle into N subintervals, and create a triangular grid. This defines ((N+1)*(N+2))/2 points that lie on the intersections of grid lines. The arrangement is suggested by this diagram:

              X
             9 X
            8 9 X
           7 8 9 X
          6 7 8 9 X
         5 6 7 8 9 X
        4 5 6 7 8 9 X
       3 4 5 6 7 8 9 X
      2 3 4 5 6 7 8 9 X
     1 2 3 4 5 6 7 8 9 X
    0 1 2 3 4 5 6 7 8 9 X
      

The library includes a routine which allows the user to pick an arbitrary triangle and an arbitrary number of subdivisions. It then returns the triangular gridpoints defined by that choice.

Licensing:

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

Languages:

TRIANGLE_GRID is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

BALL_GRID, a FORTRAN77 library which computes grid points that lie inside a 3D ball.

CIRCLE_ARC_GRID, a FORTRAN77 program which computes points equally spaced along a circular arc;

CIRCLE_GRID, a FORTRAN77 library which computes a grid of points inside a circle.

ELLIPSE_GRID, a FORTRAN77 library which computes grid points that lie inside an ellipse.

ELLIPSOID_GRID, a FORTRAN77 library which computes grid points that lie inside a 3D ellipsoid.

TETRAHEDRON_GRID, a FORTRAN77 library which computes a tetrahedral grid of points.

Source Code:

• triangle_grid.f, the source code.
• triangle_grid.sh, BASH commands to compile the source code.

Examples and Tests:

• triangle_grid_prb.f, a sample calling program.
• triangle_grid_prb.sh, BASH commands to compile and run the sample program.
• triangle_grid_prb_output.txt, the output file.
• triangle_grid_test01.xy, a grid of 66 points, generated by subdividing by 10 each side of the (0,0), (1,0), (1/2,sqrt(3)/2) triangle.
• triangle_grid_test01.png, an image of the points.

List of Routines:

• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TRIANGLE_GRID computes points on a triangular grid.

You can go up one level to the FORTRAN77 source codes.