Name
ST_GeneratePoints — Generates a multipoint of random points contained in a Polygon or MultiPolygon.
Synopsis
geometry ST_GeneratePoints(geometry g, integer npoints, integer seed = 0);
Description
ST_GeneratePoints generates a multipoint consisting of a given number of pseudo-random points
which lie within the input area.
The optional seed is used to regenerate a deterministic sequence of points,
and must be greater than zero.
Availability: 2.3.0
Enhanced: 3.0.0, added seed parameter
Examples
Generated a multipoint consisting of 12 Points overlaid on top of original polygon using a random seed value 1996
SELECT ST_GeneratePoints(geom, 12, 1996)
FROM (
SELECT ST_Buffer(ST_GeomFromText('LINESTRING(50 50,150 150,150 50)'),
10, 'endcap=round join=round') AS geom
) AS s;
Given a table of polygons s, return 12 individual points per polygon. Results will be different each time you run.
SELECT s.id, dp.path[1] AS pt_id, dp.geom FROM s, ST_DumpPoints(ST_GeneratePoints(s.geom,12)) AS dp;
Generate dot-density points from a polygon table, using the absolute value of an attribute as the number of points and keeping the sign of the attribute for styling.
SELECT z.id,
CASE WHEN z.count_delta < 0 THEN -1 ELSE 1 END AS sign,
dp.path[1] AS pt_id,
dp.geom
FROM zones AS z
CROSS JOIN LATERAL ST_DumpPoints(
ST_GeneratePoints(z.geom, abs(z.count_delta)::integer, z.id + 1)
) AS dp
WHERE z.count_delta <> 0;