add orientations

content/api/vision/_index.md

@@ -20,6 +20,7 @@ The markers in the list have some useful attributes:
 - `pixel_centre` - returns the location in pixels of the centre of the marker in the captured image.
 - `cartesian` - returns details of the position of the marker in the [Cartesian](coordinates/#cartesian-coordinates) coordinate system.
 - `spherical` - returns details of the position of the marker in a [spherical](coordinates/#spherical-coordinates) coordinate system.
+- `orientation` - returns the rotation of the marker around its centre. See [Orientation](coordinates/#orientation) for its coordinate system.
 - `polar` - *Deprecated*. Use the `spherical` attribute instead.
 
 {{% notice tip %}}

content/api/vision/coordinates.md

@@ -47,9 +47,22 @@ robot, exactly 1 metre away.
 
 {{% added_in update="2018-jan" feature="spherical coordinates" %}}
 
-## Diagram
+### Diagram
 
 The following diagram shows the orientation of the Cartesian axes relative to
 the camera as well as the angles which describe the spherical coordinate space.
 
 ![A diagram showing the coordinate spaces](/img/api/coordinate-spaces.svg)
+
+## Orientation Coordinates
+
+Orientation represents the rotation of a marker around the x, y, and z axes.
+Rotations are applied in order of Z, Y, X.
+
+The following table visually explains what positive and negative rotations represent.
+|  |  |
+|:-:|:-:|
+| <img src="/img/api/coordinate-orientations/m45x0y0z.png?width=200px" style="margin:0"/> `rot_x_degrees = 45` | <img src="/img/api/coordinate-orientations/m-45x0y0z.png?width=200px" style="margin:0"/>  `rot_x_degrees = -45` |
+| <img src="/img/api/coordinate-orientations/m0x45y0z.png?width=200px" style="margin:0"/> `rot_y_degrees = 45` |  <img src="/img/api/coordinate-orientations/m0x-45y0z.png?width=200px" style="margin:0"/> `rot_y_degrees = -45` |
+| <img src="/img/api/coordinate-orientations/m0x0y45z.png?width=200px" style="margin:0"/> `rot_z_degrees = 45` |  <img src="/img/api/coordinate-orientations/m0x0y-45z.png?width=200px" style="margin:0"/>  `rot_z_degrees= -45` |
+|  <img src="/img/api/coordinate-orientations/m0x0y0z.png?width=200px" style="margin:0"/> `0` in all axes  |