ST_VoronoiPolygons-PolarDB(PolarDB)-阿里云帮助中心

Returns the cells of the Voronoi diagram constructed from the vertices of a geometry.

Syntax

geometry ST_VoronoiPolygons(geometry g1, float tolerance = 0.0, geometry extend_to = NULL);

Parameters

Parameter	Type	Default	Description
`g1`	geometry	—	The input geometry whose vertices are used to build the Voronoi diagram.
`tolerance`	float	0.0	The distance within which two vertices are treated as coincident. Set a non-zero value to improve the robustness of the algorithm.
`extend_to`	geometry	NULL	The envelope that the Voronoi diagram is extended to cover. If NULL, the diagram extends to a bounding box expanded by approximately 50% in each direction from the input geometry. If specified, the diagram covers this envelope unless it is smaller than the default envelope.

Return value

Returns a GeometryCollection of Polygon geometries. The envelope of the collection is larger than the extent of the vertices of the input geometry.

Usage notes

If g1 is NULL, the function returns NULL.
If g1 contains only one vertex, the function returns an empty GeometryCollection.
If the area of the envelope specified by extend_to is zero, the function returns an empty GeometryCollection.

Example

The following example shows how the output differs when extend_to is set to different values.

SELECT ST_VoronoiPolygons(g,0,e),g,e
             from (select ST_Buffer('LINESTRING(0 0,3 0,3 3)'::geometry,1,'join=mitre endcap=square') as g,
                    ST_Buffer('POINT(-1 -1)'::geometry,10) as e) as t;