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 Unity.Robotics.ROSTCPConnector;
using RosColor = RosMessageTypes.RoboticsDemo.MUnityColor;

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.

• 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

Please reference networking troubleshooting doc if any errors are thrown.

Continue to the ROS–Unity Integration Service.