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

Converts a meshgeom geometry object into a triangulated representation optimized for rendering.

Syntax

meshgeom ST_Triangulate(meshgeom geom);

Parameters

Parameter	Description
`geom`	The `meshgeom` object to triangulate.

Description

ST_Triangulate decomposes polygon patches in a meshgeom object into indexed triangle surfaces (INDEXSURFACE), where each face is represented as a set of vertex indices (INDEX). The returned triangulated geometry object is used to render models.

The function accepts both polygon-based patches (PATCH(POLYGON(...))) and pre-indexed surface patches (PATCH(INDEXSURFACE(...))), and produces the same INDEXSURFACE Z output in both cases.

Examples

Triangulate a polygon patch

Input is a PATCH containing a POLYGON. ST_Triangulate splits the polygon into two triangles and returns an indexed surface.

SELECT ST_asText(ST_Triangulate('MESHGEOM(PATCH(POLYGON((0 0 0, 1 0 0, 1 1 0, 0 1 0, 0 0 0))))'));

Output:

MESHGEOM(PATCH(INDEXSURFACE Z (VERTEX(0 0 0,1 0 0,1 1 0,0 1 0),INDEX((2,3,0),(0,1,2)))))

Triangulate an indexed surface patch

Input is already an INDEXSURFACE with a single quad index. ST_Triangulate re-triangulates it, producing the same output as the polygon input above.

SELECT ST_asText(ST_Triangulate('MESHGEOM(PATCH(INDEXSURFACE( VERTEX(0 0 0,1 0 0,1 1 0,0 1 0),INDEX((0,1,2,3)) )))'));

Output:

MESHGEOM(PATCH(INDEXSURFACE Z (VERTEX(0 0 0,1 0 0,1 1 0,0 1 0),INDEX((2,3,0),(0,1,2)))))

What's next

ST_asText — convert a meshgeom object to its well-known text (WKT) representation
Other Ganos geometry functions for building, transforming, and exporting meshgeom objects