Add a section on simulated robot sensor inputs

Author: PeterJCLaw

simulator/simulated_robot.md

@@ -73,6 +73,8 @@ This is shown as a red coloured block on the robot. You can access the servo usi
 
 ### Distance Sensors
 
+<!-- Changing this? Consider updating the "Simulated robot inputs" section in `simulator/using_the_simulator.md` -->
+
 Analogous to [ultrasound sensors](https://robocraze.com/blogs/post/what-is-ultrasonic-sensor), distance sensors allow you to retrieve the distance between your robot and an object. These are attached to analog pins A0-A5:
 
 | Pin | Location    | Required Mode |
@@ -104,10 +106,12 @@ Using the `digital_write` method, you can set these to `True` (On) or `False` (O
 
 ## Vision
 
+<!-- Changing this? Consider updating the "Simulated robot inputs" section in `simulator/using_the_simulator.md` -->
+
 The simulated robot has a camera which provides position and orientation
 information about other objects within the simulation. This simulates the
 system of fiducial markers which the physical robot's camera can detect.
 
-You can access the camera with `robot.camera`. The simulated vision system matches the physical robot's vision API, so please use the [vision programming docs page]({{ site.baseurl }}/programming/vision/) as a reference. There are a few small differences between the simulator and the physical kit which are noted on that page. 
+You can access the camera with `robot.camera`. The simulated vision system matches the physical robot's vision API, so please use the [vision programming docs page]({{ site.baseurl }}/programming/vision/) as a reference. There are a few small differences between the simulator and the physical kit which are noted on that page.
 
-[arduino-programming]: {{ site.baseurl }}/programming/arduino/sr_firmware
+[arduino-programming]: {{ site.baseurl }}/programming/arduino/sr_firmware

simulator/using_the_simulator.md

@@ -118,3 +118,16 @@ In the simulator, all logs are prefixed with the zone that the robot code is run
 ~~~~~
 
 This makes it possible to distinguish which logs are from which robot when they are viewed in Webots console panel.
+
+## Simulated robot inputs
+
+By default Webots will show an overlay of what the robot's [camera]({{ site.baseurl }}/simulator/simulated_robot#vision) can see in the top right of the simulation window.
+This can be useful to understand how the robot sees its world.
+Double-clicking this overlay will move the overlay to its own window.
+
+Note that the view provided by Webots may include highlights of simulated markers which a real camera would not be able to see.
+These are filtered out for you by the simulated SR API.
+
+The robot also features [distance sensors]({{ site.baseurl }}/simulator/simulated_robot#distance-sensors).
+To better understand how these sensors perceive the world it is possible to turn on a display of their interactions with the simulated world.
+Go to the menu **View** → **Optional Rendering** and select the option **Show DistanceSensor Rays**.