PostGIS
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 + zoffAll 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' = zThis 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
|
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_AsEWKT(ST_Affine(geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0, 1, 0, 0, 0)) As using_affine,
ST_AsEWKT(ST_Rotate(geom, pi())) As using_rotate
FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') 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_AsEWKT(ST_Affine(geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0))
FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') As geom) As foo;
st_asewkt
-------------------------------
LINESTRING(-1 -2 -3,-1 -4 -3)
(1 row)