PostgreSQL/PostGIS - Create regular (equilateral & equiangular) Polygons (i.e. Hexagons, Pentagons, ...).

ST_MakeAGon.sql

/*
 * @in_params
 * center - center POINT geometry
 * radius - circumradius [in CRS units] (cirlce that inscribes the *gon)
 * sides  - desired side count (e.g. 6 for Hexagon)
 * skew   - rotation offset, clockwise [in degree]; DEFAULT 0.0 (corresponds to planar NORTH)
 *
 * @out_params
 * agon   - resulting *gon POLYGON geometry
 *
 *
 * The function will create a @sides sided regular, equilateral & equiangular Polygon
 * from a given @center and @radius and optional @skew offset from NORTH
 */
 
CREATE OR REPLACE FUNCTION ST_MakeAGon(
  IN  center   GEOMETRY(POINT),
  IN  radius   FLOAT8,
  IN  sides    INT,
  IN  skew     FLOAT8 DEFAULT 0.0,
  OUT agon     GEOMETRY(POLYGON)
) LANGUAGE 'plpgsql' IMMUTABLE STRICT PARALLEL SAFE AS
  $$
  DECLARE
    _x FLOAT8  := ST_X($1);
    _y FLOAT8  := ST_Y($1);
	
    _cr FLOAT8 := 360.0/$3;
		
    __v GEOMETRY(POINT)[];
	
  BEGIN
    FOR i IN 0..$3 LOOP
      __v[i] := ST_MakePoint(_x + $2*SIND(i*_cr + $4), _y + $2*COSD(i*_cr + $4));
    END LOOP;
		
    agon := ST_MakePolygon(ST_MakeLine(__v));
  END;
  $$
;