Description

Returns the 1-based Nth face of a PolyhedralSurface or TIN. Returns NULL for other geometries or an out-of-range index. Use this function to access faces, because ST_GeometryN treats PolyhedralSurface and TIN as unitary geometries.

	Index is 1-based.

	If you want to extract all elements of a geometry ST_Dump is more efficient.

Availability: 2.0.0

This method implements the SQL/MM specification. SQL-MM ISO/IEC 13249-3: 8.5

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

Extract the 2nd face of the polyhedral surface.

SELECT ST_PatchN(geom, 2) As geomewkt
FROM (
VALUES ('POLYHEDRALSURFACE( ((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
    ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
    ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
    ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)) )'::geometry) ) As foo(geom);

POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))

010300008001000000050000000000000000000000000000000000000000000000000000000000000000000000000000000000F03F0000000000000000000000000000F03F000000000000F03F0000000000000000000000000000F03F00000000000000000000000000000000000000000000000000000000000000000000000000000000

Figure

See Also

ST_AsEWKT, ST_GeomFromEWKT, ST_Dump, ST_GeometryN, ST_NumGeometries, ST_NumPatches