Name
ST_Affine — Apply a 3D affine transformation to a geometry.
Synopsis
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);
Description
Applies a 3D affine transformation to the geometry to do things like translate, rotate, scale in one step.
Version 1: The call
ST_Affine(geom, a, b, c, d, e, f, g, h, i, xoff, yoff, zoff)
represents the transformation matrix
/ a b c xoff \ | d e f yoff | | g h i zoff | \ 0 0 0 1 /
and the vertices are transformed as follows:
x' = a*x + b*y + c*z + xoff y' = d*x + e*y + f*z + yoff z' = g*x + h*y + i*z + zoff
All of the translate / scale functions below are expressed via such an affine transformation.
Version 2: Applies a 2d affine transformation to the geometry. The call
ST_Affine(geom, a, b, d, e, xoff, yoff)
represents the 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 /
and the vertices are transformed as follows:
x' = a*x + b*y + xoff y' = d*x + e*y + yoff z' = z
This method is a subcase of the 3D method above.
Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
Availability: 1.1.2. Name changed from Affine to ST_Affine in 1.2.2
![[Note]](../images/note.png)
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Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+ |
This function supports Polyhedral surfaces.
This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).
This function supports 3d and will not drop the z-index.
This method supports Circular Strings and Curves.
Examples
Rotate a 3D line 180 degrees about the z axis. Note this is long-hand for doing ST_Rotate();
SELECT ST_Affine(geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0, 1, 0, 0, 0) As using_affine,
ST_Rotate(geom, pi()) As using_rotate
FROM (SELECT 'LINESTRING(1 2 3,1 4 3)'::geometry As geom) As foo;
using_affine | using_rotate -----------------------------+----------------------------- LINESTRING(-1 -2 3,-1 -4 3) | LINESTRING(-1 -2 3,-1 -4 3) (1 row)
Rotate a 3D line 180 degrees in both the x and z axis.
SELECT ST_Affine(geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0)
FROM (SELECT 'LINESTRING(1 2 3,1 4 3)'::geometry As geom) As foo;
LINESTRING(-1 -2 -3,-1 -4 -3)