Example: Camera World

A minimal custom setup — one SDF world with a ground plane, a red box, and a static camera sensor. The camera’s Gazebo image topic is bridged into ROS 2, and a small Python node subscribes and logs frame size + FPS.

Use it as a template when you want to write your own world and your own node from scratch without pulling in a whole robot stack.

Source: examples/camera_world/. Jazzy only (the bridge type strings differ on Humble — see the bottom of this page).

Layout

examples/camera_world/
├── worlds/camera_world.sdf           # world + camera sensor
├── launch/camera_demo.launch.py      # gz sim + bridge + subscriber
└── src/camera_subscriber/            # ROS 2 python package
    └── camera_subscriber/image_consumer.py

Runs on the base gazebo-ros-setup image — no extra apt packages needed.

1. Drop the package into the workspace

The container mounts ./workspace → /workspace. The examples/ folder is not mounted by default, so copy what you need in:

cp -r examples/camera_world/src/camera_subscriber workspace/src/
cp -r examples/camera_world/launch examples/camera_world/worlds workspace/

2. Build

docker compose up -d
docker compose exec ros-gazebo zsh
# inside:
cd /workspace && colcon build --symlink-install

New shells auto-source install/setup.zsh; for the current shell run it manually.

3. Launch

ros2 launch /workspace/launch/camera_demo.launch.py

What you should see:

A Gazebo window with a red box on a grey plane.

In the terminal:

[image_consumer]: Subscribed to /camera/image
[image_consumer]: First frame: 640x480 encoding=rgb8 step=1920 bytes=921600
[image_consumer]: 58 frames in 2.00s (29.0 fps)

4. Run the pieces manually (debugging)

When the combined launch hides what’s going on:

# shell 1 — simulator
gz sim -r /workspace/worlds/camera_world.sdf

# shell 2 — bridge
ros2 run ros_gz_bridge parameter_bridge \
    /camera/image@sensor_msgs/msg/Image@gz.msgs.Image

# shell 3 — verify
ros2 topic list                  # /camera/image should appear
ros2 topic hz /camera/image      # ~30 Hz
ros2 run rqt_image_view rqt_image_view /camera/image

If /camera/image isn’t on the ROS side, check the gz side first: gz topic -l. The bridge argument is <topic>@<ROS type>@<gz type>.

How the pieces connect

  ┌─────────────┐   gz topic          ┌──────────────┐   ROS 2 topic
  │  gz sim     │  /camera/image  →   │ parameter_   │  /camera/image  →  image_consumer
  │  (SDF world │  gz.msgs.Image      │ bridge       │  sensor_msgs/Image
  │  + sensor)  │                     └──────────────┘
  └─────────────┘

Extending it

Add more models and watch the frame change live.
Swap the static camera for one mounted on a movable base + cmd_vel.
Add <sensor type="depth_camera"> and bridge the depth topic.
Add ros-jazzy-cv-bridge and replace the logging with OpenCV processing.

See Writing Your Own Nodes for the package-creation workflow in general.

Humble note

On Humble, the bridge gz type is ignition.msgs.Image (not gz.msgs.Image), the simulator is Fortress, and the SDF plugin names (ignition-gazebo-*) differ. This example is only tested on Jazzy + gz-harmonic.