ST_TESSELATE
Signature
GEOMETRY ST_TESSELATE(GEOMETRY geom)
Description
Return the tessellation of a geometry with adaptive triangles.
Remark
Input geometry (geom) can only be a POLYGON or a MULTIPOLYGON.
Examples
Case with POLYGON
SELECT ST_TESSELATE('POLYGON ((1 1, 1 5, 3 5, 3 4, 2 4,
2 3, 4 3, 4 2, 1 1))');
-- Answer:
GEOMETRYCOLLECTION (POLYGON ((1 5, 3 5, 3 4, 1 5)),
POLYGON ((2 3, 4 3, 4 2, 2 3)),
POLYGON ((1 5, 3 4, 2 4, 1 5)),
POLYGON ((2 3, 4 2, 1 1, 2 3)),
POLYGON ((1 1, 1 5, 2 4, 1 1)),
POLYGON ((2 4, 2 3, 1 1, 2 4)))
Case with MULTIPOLYGON
SELECT ST_TESSELATE('MULTIPOLYGON (
((1 1, 1 3, 2 4, 3 3, 3 2, 2 2, 1 1)),
((3 5, 4 3, 4 2, 3 1, 5 1, 5 4, 3 5)))');
-- Answer:
GEOMETRYCOLLECTION (POLYGON ((1 1, 1 3, 2 4, 1 1)),
POLYGON ((2 4, 3 3, 3 2, 2 4)),
POLYGON ((2 2, 1 1, 2 4, 2 2)),
POLYGON ((2 4, 3 2, 2 2, 2 4)),
POLYGON ((5 1, 3 1, 4 2, 5 1)),
POLYGON ((4 3, 3 5, 5 4, 4 3)),
POLYGON ((5 4, 5 1, 4 2, 5 4)),
POLYGON ((4 2, 4 3, 5 4, 4 2)))
Application with real data
The tessellation is made on a set of urban plots (in grey) (stored in a layer called “PLOTS”)
SELECT ST_TESSELATE(THE_GEOM) as THE_GEOM FROM PLOTS;
The resulting triangles are displayed in pink.
