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Understanding Topics in ROS 2
Discover how ROS 2 topics enable real-time data sharing between nodes using pub/sub messaging.
In ROS 2, a topic is a one-way data stream — it lets one node publish data, and others subscribe to it in real time. This pub/sub pattern is perfect for high-frequency data like joint states, velocity commands, or LiDAR scans.Isaac Sim takes full advantage of topics to mirror real-world robotics behavior inside a fully controlled simulation. Whether you're publishing synthetic sensor data or subscribing to simulated robot states, topics are the backbone of real-time interaction.
🔍 Why It Matters in Isaac
Isaac Sim is all about reproducing physical systems in simulation, and topics make that possible. Here's how:
- Sensor Simulation: A simulated RGB camera inside Isaac can publish images to
/camera/image_raw. Your computer vision algorithm (in another node) can subscribe to that topic and process images as if they were coming from a real robot. - Motion Commands: You can publish velocity commands to
/cmd_vel, and your Isaac-simulated robot will move accordingly — just like in the real world. - Testing at Scale: Want to see how your algorithm performs with imperfect data? Inject simulated noise into a topic (e.g., add Gaussian blur to camera feed) and evaluate how your system holds up — no hardware risk involved.
🧠 Developer Tip
In Isaac Sim, topics can also be visualized and debugged using ROS 2 bridge tools or custom dashboards. Always check ros2 topic list, ros2 topic echo, and ros2 topic hz to inspect what’s flowing through the system.
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