ROSBridgeLib

A Unity library for communication with ROS through RosBridge

foo@bar:~$ sudo apt-get install ros-<rosdistro>-rosbridge-suite
foo@bar:~$ source /opt/ros/<rosdistro>/setup.bash
foo@bar:~$ roslaunch rosbridge_server rosbridge_websocket.launch

The first version of this I believe origins from Michael Jenkin, in the repo unityros. He made a sample unity project showing turtlesim, with good instructions on how to use this project. All honor goes to him. I created this project because there was no repository containing the barebone library.

Included messages

This repository does not contain every ROS message. If you need to add one, please make a pull request.

Documentation

Documentation is in the code. I added some more in addition to what Michael Jenkin (original author) did. The main file is ROSBridgeWebSocketConnection.cs, which sets up everything.

Installation

Clone this repository in to the Assets folder of an Unity project:

foo@bar:~$  git clone --recurse-submodules https://github.com/MathiasCiarlo/ROSBridgeLib.git

Example usage

This is an example application where a ball is controlled. Basically, there are three important script types to notice.

Setup the connection

First, create a main script, ROSInitializer.cs responsible for initializing RosBridge. Attach this to a GameObject, say Main Camera:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using ROSBridgeLib;

public class ROSInitializer : MonoBehaviour
{
   public ROSBridgeWebSocketConnection ros = null;
    
  void Start() {
    // Where the rosbridge instance is running, could be localhost, or some external IP
    ros = new ROSBridgeWebSocketConnection ("ws://localhost", 9090);

    // Add subscribers and publishers (if any)
    ros.AddSubscriber (typeof(BallPoseSubscriber));
    ros.AddPublisher (typeof(BallTwistPublisher));

    // Fire up the subscriber(s) and publisher(s)
    ros.Connect ();
  }
  
  // Extremely important to disconnect from ROS. Otherwise packets continue to flow
  void OnApplicationQuit() {
    if(ros!=null) {
      ros.Disconnect ();
    }
  }
  // Update is called once per frame in Unity
  void Update () {
    ros.Render ();
  }
}

Subscriber

Then, create a subscriber script, BallPoseSubscriber.cs, which will receive updates from a chosen ROS topic

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

using ROSBridgeLib;
using SimpleJSON;
using ROSBridgeLib.geometry_msgs;


public class BallPoseSubscriber : ROSBridgeSubscriber
{
  static GameObject ball;
  
  // These two are important
  public new static string GetMessageTopic() {
    //Topic name is up to the user. It should return the full path to the topic. 
    //For eg, "/turtle1/cmd_vel" instead of "/cmd_vel".
    return "/pose_info";
  }

  public new static string GetMessageType() {
    //Same as the definition present in ROS documentation:
    return "geometry_msgs/Pose";
  }

  // Important function (I think.. Converts json to PoseMsg)
  public new static ROSBridgeMsg ParseMessage(JSONNode msg) {
    return new PoseMsg (msg);
  }

  // This function should fire on each received ros message
  public new static void CallBack(PoseMsg msg) {
    
    Debug.Log("Recieved Message : "+msg.ToYAMLString());
    // Update ball position, or whatever
    ball=GameObject.Find("ball");
    Vector3 ballPos=ball.transform.position;
    ballPos.x = msg.GetPosition().GetX();
    ballPos.y = msg.GetPosition().GetY();
    ballPos.z = msg.GetPosition().GetZ();
    //Changing ball's position to the updated position vector
    ball.transform.position=ballPos;
  }
}

Verify the subscriber by running:

foo@bar:~$ rostopic pub -1 /pose_info geometry_msgs/Pose -- '[1.0,1.0,1.0]' '[1.0,1.0,1.0,1.0]' 

Publisher

If you need to publish data to ROS, create a publisher like BallTwistPublisher.cs:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using SimpleJSON;
using ROSBridgeLib.geometry_msgs;

public class BallTwistPublisher : ROSBridgePublisher
{
    // The following three functions are important
  public static string GetMessageTopic() {
    //topic name is up to the user
    return "/twist_info";
  }

  public static string GetMessageType() {
      return "geometry_msgs/Twist";
  }

  public static string ToYAMLString(TwistMsg msg) {
    return msg.ToYAMLString();
  }

  public new static ROSBridgeMsg ParseMessage(JSONNode msg) {
    return new TwistMsg(msg);
  }    
}

Above script defines the publisher. In order to call this publisher attach one script, DataManager.cs, to the gameobject ball.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

using ROSBridgeLib;
using ROSBridgeLib.geometry_msgs;

public class DataManager : MonoBehaviour
{
    Rigidbody rb;
    GameObject rosObj;
    //Required for TwistMsg
    Vector3Msg linearVel;
    Vector3Msg angularVel;
    TwistMsg msg;
    
    // Start is called before the first frame update
    void Start()
    {
      //Since we attached ROSInitiazer to Main Camera:
        rosObj = GameObject.Find ("Main Camera");
        rb=GetComponent<Rigidbody>();
    }

    // Update is called once per frame
    void Update()
    {
      //dependant on the message defintion:
        linearVel=new Vector3Msg(
            rb.velocity.x,
            rb.velocity.y,
            rb.velocity.z
        );
        angularVel=new Vector3Msg(
            rb.angularVelocity.x,
            rb.angularVelocity.y,
            rb.angularVelocity.z
        );
        msg=new TwistMsg(linearVel,angularVel);
        rosobj.GetComponent<ROSInitialize>().ros.Publish(
            BallTwistPublisher.GetMessageTopic(),msg
        );
    }
}

verify the publisher script:

foo@bar:~$ rostopic echo /twist_info

License

Note: SimpleJSON is included here as a convenience. It has its own licensing requirements. See source code and unity store for details.