ST_ZupToYup function to convert a Z-up coordinate system to Y-up - PolarDB

Converts the coordinate system of an sfmesh object from Z-up to Y-up.

Syntax

sfmesh ST_ZupToYup(sfmesh mesh);

Parameters

Parameter	Description
`mesh`	The `sfmesh` object to convert.

Return value

Returns an sfmesh object with the coordinate system converted from Z-up to Y-up.

Description

In some scenarios in which a Z-up coordinate system is used, the Y-up orientation is required. In these scenarios, you can use the ST_ZupToYup function to convert the coordinate system.

ST_ZupToYup is equivalent to calling ST_Affine with the following matrix transformation:

1.0, 0,   0,    0,
0,   0,   -1.0, 0,
0,   1.0, 0,    0

The transformation swaps the Y and Z axes and negates the new Z axis, which is the standard rotation for converting between these two coordinate conventions.

Example

SELECT ST_AsText(
  ST_ZupToYup(
    ST_MeshFromText(
      '{"version" : 1, "root" : 0, "meshgeoms" : ["MESHGEOM(PATCH(INDEXSURFACE Z (VERTEX(0 0 2,0 10 3,10 10 1,10 0 1),INDEX((0,1,2),(1,2,3)))))"], "primitives" : [{"meshgeom" : 0}], "nodes" : [{"primitive" : 0}]}'
    )
  )
);

Result:

{"version" : 1, "root" : 0, "meshgeoms" : ["MESHGEOM(PATCH(INDEXSURFACE Z (VERTEX(0 0 2,0 10 3,10 10 1,10 0 1),INDEX((0,1,2),(1,2,3)))))"], "primitives" : [{"meshgeom" : 0}], "nodes" : [{"primitive" : 0,"matrix" : [1,0,0,1,0,0,0,0,-1,0,0,0,0,0,0,1]}]}

The "matrix" field added to the node encodes the Z-up to Y-up affine transformation. The mesh geometry itself is unchanged; the transformation is stored as a node-level matrix and applied at render time.

What's next

ST_Affine — apply a custom affine transformation matrix to an sfmesh object