# ROS–Unity Integration: Publisher Create a simple Unity scene which publishes a GameObject's position and rotation to a [ROS topic](http://wiki.ros.org/ROS/Tutorials/UnderstandingTopics#ROS_Topics). ## Setting Up ROS - 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](setup.md) guide. - Open a new terminal window and run the following commands: ```bash 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`. - Open another new terminal window, navigate to your ROS workspace, and run the following commands: ```bash source devel/setup.bash rostopic echo pos_rot ``` ## Setting Up Unity Scene - In the menu bar, find and select `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" to generate new C# scripts from the ROS .msg files. ![](images/generate_messages_1.png) - The generated files will be saved in the default directory `Assets/RosMessages/RoboticsDemo/msg`. - Create a new directory in `Assets` and name it `Scripts` - Create a new script in the `Scripts` directory and name it `RosPublisherExample.cs` - Open `RosPublisherExample.cs` and paste the following code: - **Note** Script can be found at `tutorials/ros_unity_integration/unity_scripts` ```csharp using RosMessageTypes.RoboticsDemo; using UnityEngine; using Random = UnityEngine.Random; /// /// /// public class RosPublisherExample : MonoBehaviour { ROSConnection ros; public string topicName = "pos_rot"; // The GameObject public GameObject cube; // Publish the cube's position and rotation every N seconds public float publishMessageFrequency = 0.5f; // Used to determine how much time has elapsed since the last message was published private float timeElapsed; void Start() { // start the ROS connection ros = ROSConnection.instance; } private void Update() { timeElapsed += Time.deltaTime; if (timeElapsed > publishMessageFrequency) { cube.transform.rotation = Random.rotation; PosRot cubePos = new PosRot( cube.transform.position.x, cube.transform.position.y, cube.transform.position.z, cube.transform.rotation.x, cube.transform.rotation.y, cube.transform.rotation.z, cube.transform.rotation.w ); // Finally send the message to server_endpoint.py running in ROS ros.Send(topicName, cubePos); timeElapsed = 0; } } } ``` - Add a plane and a cube to the empty Unity scene - Move the cube a little ways up so it is hovering above the plane - In the main menu bar, open `Robotics/ROS Settings`. - Set the ROS IP address and port to match the ROS IP and port variables defined when you set up ROS. - Create another empty GameObject, name it `RosPublisher` and attach the `RosPublisherExample` script. - Drag the cube GameObject onto the `Cube` parameter. - Pressing play in the Editor should publish a message to the terminal running the `rostopic echo pos_rot` command every 0.5 seconds ![](images/tcp_1.gif) Continue to the [ROS Subscriber](subscriber.md) tutorial.