Unity-Robotics-Hub/tutorials/ros_unity_integration/subscriber.md

ROS–Unity Integration: Subscriber

Create a simple Unity scene which subscribes to a ROS topic to change the colour of a GameObject.

Setting Up ROS

(Skip to Setting Up Unity Scene if you already did the Publisher tutorial.)

• Copy the tutorials/ros_packages/robotics_demo folder of this repo into the src folder in your Catkin workspace.

• Follow the ROS–Unity Initial Setup guide.

• Open a new terminal window, navigate to your Catkin workspace, and run the following commands:

   source devel/setup.bash
   rosrun robotics_demo server_endpoint.py
  

Once the server_endpoint has started, it will print something similar to [INFO] [1603488341.950794]: Starting server on 192.168.50.149:10000.

• In Unity, we need to generate the C# code for the UnityColor message. Open Robotics -> Generate ROS Messages....
  • Set the ROS message path to PATH/TO/Unity-Robotics-Hub/tutorials/ros_packages/robotics_demo/, expand the robotics_demo subfolder and click Build 2 msgs.

• The generated files will be saved in the default directory Assets/RosMessages/RoboticsDemo/msg.

Setting Up Unity Scene

• Create a script and name it RosSubscriberExample.cs
• Paste the following code into RosSubscriberExample.cs
  • Note Script can be found at tutorials/ros_unity_integration/unity_scripts

using UnityEngine;
using RosColor = RosMessageTypes.RoboticsDemo.UnityColor;

public class RosSubscriberExample : MonoBehaviour
{
    public GameObject cube;

    void Start()
    {
        ROSConnection.instance.Subscribe<RosColor>("color", ColorChange);
    }

    void ColorChange(RosColor colorMessage)
    {
        cube.GetComponent<Renderer>().material.color = new Color32((byte)colorMessage.r, (byte)colorMessage.g, (byte)colorMessage.b, (byte)colorMessage.a);
    }
}

• Create an empty GameObject and name it RosSubscriber

• Attach the RosSubscriberExample script to the RosSubscriber GameObject and drag the cube GameObject onto the cube parameter in the Inspector window.

• From the Unity menu bar, open Robotics/ROS Settings, and set the ROS IP Address variable to your ROS IP.

  • Unlike the previous tutorial, using a subscriber requires an incoming connection from ROS to Unity. You may need to adjust your firewall settings for this to work.
  • The IP for Unity to listen on should be determined automatically, but if you're having trouble, you can set it manually in the Override Unity IP field. Finding the IP address of your local machine (the one running Unity) depends on your operating system.
    • On a Mac, open System Preferences > Network. Your IP address should be listed on the active connection.
    • On Windows, click the Wi-Fi icon on the taskbar, and open Properties. Your IP address should be listed near the bottom, next to "IPv4 address."

• Press play in the editor

In ROS Terminal Window

• After the scene has entered Play mode, run the following command: rosrun robotics_demo color_publisher.py to change the color of the cube GameObject in Unity to a random color

Continue to the ROS–Unity Integration Service.