Name
ST_TriangulatePolygon — Computes the constrained Delaunay triangulation of polygons
Synopsis
geometry ST_TriangulatePolygon(geometry geom);
Description
Computes the constrained Delaunay triangulation of polygons. Holes and Multipolygons are supported.
The "constrained Delaunay triangulation" of a polygon is a set of triangles formed from the vertices of the polygon, and covering it exactly, with the maximum total interior angle over all possible triangulations. It provides the "best quality" triangulation of the polygon.
Availability: 3.3.0.
Requires GEOS >= 3.11.0.
Example
Triangulation of a square.
SELECT ST_AsText(
ST_TriangulatePolygon('POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))'));
st_astext
---------------------------------------------------------------------------
GEOMETRYCOLLECTION(POLYGON((0 0,0 1,1 1,0 0)),POLYGON((1 1,1 0,0 0,1 1)))
Example
Triangulation of the letter P.
SELECT ST_AsText(ST_TriangulatePolygon(
'POLYGON ((26 17, 31 19, 34 21, 37 24, 38 29, 39 43, 39 161, 38 172, 36 176, 34 179, 30 181, 25 183, 10 185, 10 190, 100 190, 121 189, 139 187, 154 182, 167 177, 177 169, 184 161, 189 152, 190 141, 188 128, 186 123, 184 117, 180 113, 176 108, 170 104, 164 101, 151 96, 136 92, 119 89, 100 89, 86 89, 73 89, 73 39, 74 32, 75 27, 77 23, 79 20, 83 18, 89 17, 106 15, 106 10, 10 10, 10 15, 26 17), (152 147, 151 152, 149 157, 146 162, 142 166, 137 169, 132 172, 126 175, 118 177, 109 179, 99 180, 89 180, 80 179, 76 178, 74 176, 73 171, 73 100, 85 99, 91 99, 102 99, 112 100, 121 102, 128 104, 134 107, 139 110, 143 114, 147 118, 149 123, 151 128, 153 141, 152 147))'
));
Polygon Triangulation
Same example as ST_Tesselate
SELECT ST_TriangulatePolygon(
'POLYGON (( 10 190, 10 70, 80 70, 80 130, 50 160, 120 160, 120 190, 10 190 ))'::geometry
);
ST_AsText output
GEOMETRYCOLLECTION(POLYGON((50 160,120 190,120 160,50 160))
,POLYGON((10 70,80 130,80 70,10 70))
,POLYGON((50 160,10 70,10 190,50 160))
,POLYGON((120 190,50 160,10 190,120 190))
,POLYGON((80 130,10 70,50 160,80 130)))
 Original polygon |
 Triangulated Polygon |