PolarDB:ST_Affine

Syntax

geometry  ST_Affine(geometry  geomA , float  a , float  b , float  c , float  d , float  e , float  f , float  g , float  h , float  i , float  xoff , float  yoff , float  zoff);
geometry  ST_Affine(geometry  geomA , float  a , float  b , float  d , float  e , float  xoff , float  yoff);

Parameters

Description

• Method 1: If the expression of the ST_Affine function is ST_Affine(geom, a, b, c, d, e, f, g, h, i, xoff, yoff, zoff), the function represents the following transformation matrix:

  / a  b  c  xoff \
  | d  e  f  yoff |
  | g  h  i  zoff |
  \ 0  0  0     1 /

• The following expressions show how vertices of the geometry object are transformed. All translation and scaling functions are represented by an affine transformation.

  x' = a*x + b*y + c*z + xoff
  y' = d*x + e*y + f*z + yoff
  z' = g*x + h*y + i*z + zoff

• Method 2: If the expression of the ST_Affine function is ST_Affine(geom, a, b, d, e, xoff, yoff), the function represents the following transformation matrix:

  /  a  b  0  xoff  \       /  a  b  xoff  \
  |  d  e  0  yoff  | rsp.  |  d  e  yoff  |
  |  0  0  1     0  |       \  0  0     1  /
  \  0  0  0     1  /

• The following expressions show how the vertices of the geometry object are transformed:

  x' = a*x + b*y + xoff
  y' = d*x + e*y + yoff
  z' = z

  This method is a subcase of the preceding 3D methods.

• This function supports circular strings, curves, polyhedral surfaces, triangles, triangulated irregular network (TIN) surfaces, and 3D objects.

Examples

SELECT ST_AsEWKT(ST_Affine(ST_GeomFromEWKT('POINT(1 2 3)'),
                           cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0));
    st_asewkt
-----------------
 POINT(-1 -2 -3)
(1 row)