Grid Points in a Polygon

**POLYGON_GRID**,
a C library which
generates a grid of points
over the interior of a polygon in 2D.

The program relies on a simple idea in which the "vertex centroid" (average of the vertices) is computed, allowing the polygon to be triangulated. Each triangle can then easily be gridded. The collection of triangular grids joins up to form a grid over the polygon, although the spacing of the the grid points will vary from triangle to triangle.

The program really only works properly for convex polygons. If the polygon is not convex, then the vertex centroid need not lie inside the polygon, consequently the grid points may also seem misaligned.

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

**POLYGON_GRID** is available in
a C version and
a C++ version and
a FORTRAN90 version and
a MATLAB version and
a Python version.

BALL_GRID, a C library which computes a grid of points over the interior of a ball in 3D.

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

CUBE_GRID, a C library which computes a grid of points over the interior of a cube in 3D.

DISK_GRID, a C library which computes a grid of points over the interior of a disk in 2D.

ELLIPSE_GRID, a C library which computes a grid of points over the interior of an ellipse in 2D.

ELLIPSOID_GRID, a C library which computes a grid of points over the interior of an ellipsoid in 3D.

HYPERCUBE_GRID, a C library which computes a grid of points over the interior of a hypercube in M dimensions.

LINE_GRID, a C library which computes a grid of points over the interior of a line segment in 1D.

PYRAMID_GRID, a C library which computes a grid of points over the interior of the unit pyramid in 3D;

SIMPLEX_GRID, a C library which generates a grid of points over the interior of a simplex in M dimensions.

SPHERE_FIBONACCI_GRID, a C library which computes a grid of points using the Fibonacci spiral over the surface of a sphere in 3D.

SPHERE_GRID, a C library which provides a number of ways of generating grids of points, or of points and lines, or of points and lines and faces, on the surface of the unit sphere in 3D.

SPHERE_LLQ_GRID, a C library which uses longitudes and latitudes to create grids of points, lines, and quadrilaterals on the surface of the unit sphere in 3D.

SPHERE_LLT_GRID, a C library which uses longitudes and latitudes to create grids of points, lines, and triangles on the surface of the unit sphere in 3D.

SQUARE_GRID, a C library which computes a grid of points over the interior of a square in 2D.

TETRAHEDRON_GRID, a C library which computes a grid of points over the interior of a tetrahedron in 3D.

TRIANGLE_GRID, a C library which computes a grid of points over the interior of a triangle in 2D.

WEDGE_GRID, a C library which computes a grid of points over the interior of the unit wedge in 3D.

- polygon_grid.c, the source code.
- polygon_grid.sh, compiles the source code.
- polygon_grid.h, the include file.