ST_VoronoiPolygons-ApsaraDB RDS(RDS)-阿里云帮助中心

ST_VoronoiPolygons computes a two-dimensional Voronoi diagram from the vertices of a geometry object and returns the result as a GeometryCollection of polygons.

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 compute the Voronoi diagram.
`tolerance`	float	`0.0`	The snap distance. Vertices within this distance of each other are treated as coincident. A non-zero value improves the robustness of the algorithm.
`extend_to`	geometry	`NULL`	The envelope to which the Voronoi diagram is extended. If `NULL`, the diagram extends to a bounding box expanded by approximately 50% in each direction around the input geometry. If specified, the diagram extends to cover this envelope, unless the envelope is smaller than the default.

Return value behavior

Returns a GeometryCollection of polygons. The output envelope is larger than the extent of the input vertices.
Returns NULL if g1 is NULL.
Returns an empty GeometryCollection if g1 contains only one vertex.
Returns an empty GeometryCollection if the area of the extend_to envelope is zero.

Examples

The following example shows the differences between the return results that are obtained when the extend_to parameter 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;

Result with default envelope:

Result with custom envelope: