Using Gazebo

Added in version Jazzy: This section.

Warning

This topic is under construction and this might not even be its final form. Please feel free to open an issue if you spot any typos or other problems.

Hint

You can start the simulator with the following command.

gz sim

In this section we will see the basic operations related to Gazebo and create our own sdf file.

Basic functionality

These two official tutorials cover the basic functionality of Gazebo. They are very well made with up-to-date images and videos. Please go through them to familiarise yourself with the basic functionality.

• Understanding the GUI.

• Manipulating Models.

Fun with plugins

Check the guides below for basic functionality.

• Apply force torque plugin.

• Mouse drag plugin.

World files .sdf

See also

Official documentation: https://gazebosim.org/docs/harmonic/sdf_worlds/

Let us start with the sample scene shapes.sdf. This example is available in the official repository. It is shown below to save you a click. The format is xml, which should be a familiar file format by now.

Contents of shapes.sdf

<?xml version="1.0" ?>
<sdf version="1.11">
  <!--
    Try moving a model using the command in the following CDATA block::
  -->
  <![CDATA[
    gz service -s /world/shapes/set_pose \
               --reqtype gz.msgs.Pose --reptype gz.msgs.Boolean \
               --timeout 300 --req 'name: "box", position: {z: 5.0}'
  ]]>
  <world name="shapes">
    <scene>
      <ambient>1.0 1.0 1.0</ambient>
      <background>0.8 0.8 0.8</background>
    </scene>

    <light type="directional" name="sun">
      <cast_shadows>true</cast_shadows>
      <pose>0 0 10 0 0 0</pose>
      <diffuse>0.8 0.8 0.8 1</diffuse>
      <specular>0.2 0.2 0.2 1</specular>
      <attenuation>
        <range>1000</range>
        <constant>0.9</constant>
        <linear>0.01</linear>
        <quadratic>0.001</quadratic>
      </attenuation>
      <direction>-0.5 0.1 -0.9</direction>
    </light>

    <model name="ground_plane">
      <static>true</static>
      <link name="link">
        <collision name="collision">
          <geometry>
            <plane>
              <normal>0 0 1</normal>
              <size>100 100</size>
            </plane>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <plane>
              <normal>0 0 1</normal>
              <size>100 100</size>
            </plane>
          </geometry>
          <material>
            <ambient>0.8 0.8 0.8 1</ambient>
            <diffuse>0.8 0.8 0.8 1</diffuse>
            <specular>0.8 0.8 0.8 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="box">
      <pose>0 0 0.5 0 0 0</pose>
      <link name="box_link">
        <inertial>
          <inertia>
            <ixx>0.16666</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.16666</iyy>
            <iyz>0</iyz>
            <izz>0.16666</izz>
          </inertia>
          <mass>1.0</mass>
        </inertial>
        <collision name="box_collision">
          <geometry>
            <box>
              <size>1 1 1</size>
            </box>
          </geometry>
        </collision>

        <visual name="box_visual">
          <geometry>
            <box>
              <size>1 1 1</size>
            </box>
          </geometry>
          <material>
            <ambient>1 0 0 1</ambient>
            <diffuse>1 0 0 1</diffuse>
            <specular>1 0 0 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="cylinder">
      <pose>0 -1.5 0.5 0 0 0</pose>
      <link name="cylinder_link">
        <inertial>
          <inertia>
            <ixx>0.1458</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.1458</iyy>
            <iyz>0</iyz>
            <izz>0.125</izz>
          </inertia>
          <mass>1.0</mass>
        </inertial>
        <collision name="cylinder_collision">
          <geometry>
            <cylinder>
              <radius>0.5</radius>
              <length>1.0</length>
            </cylinder>
          </geometry>
        </collision>

        <visual name="cylinder_visual">
          <geometry>
            <cylinder>
              <radius>0.5</radius>
              <length>1.0</length>
            </cylinder>
          </geometry>
          <material>
            <ambient>0 1 0 1</ambient>
            <diffuse>0 1 0 1</diffuse>
            <specular>0 1 0 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="sphere">
      <pose>0 1.5 0.5 0 0 0</pose>
      <link name="sphere_link">
        <inertial>
          <inertia>
            <ixx>0.1</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.1</iyy>
            <iyz>0</iyz>
            <izz>0.1</izz>
          </inertia>
          <mass>1.0</mass>
        </inertial>
        <collision name="sphere_collision">
          <geometry>
            <sphere>
              <radius>0.5</radius>
            </sphere>
          </geometry>
        </collision>

        <visual name="sphere_visual">
          <geometry>
            <sphere>
              <radius>0.5</radius>
            </sphere>
          </geometry>
          <material>
            <ambient>0 0 1 1</ambient>
            <diffuse>0 0 1 1</diffuse>
            <specular>0 0 1 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="capsule">
      <pose>0 -3.0 0.5 0 0 0</pose>
      <link name="capsule_link">
        <inertial>
          <inertia>
            <ixx>0.074154</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.074154</iyy>
            <iyz>0</iyz>
            <izz>0.018769</izz>
          </inertia>
          <mass>1.0</mass>
        </inertial>
        <collision name="capsule_collision">
          <geometry>
            <capsule>
              <radius>0.2</radius>
              <length>0.6</length>
            </capsule>
          </geometry>
        </collision>
        <visual name="capsule_visual">
          <geometry>
            <capsule>
              <radius>0.2</radius>
              <length>0.6</length>
            </capsule>
          </geometry>
          <material>
            <ambient>1 1 0 1</ambient>
            <diffuse>1 1 0 1</diffuse>
            <specular>1 1 0 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="ellipsoid">
      <pose>0 3.0 0.5 0 0 0</pose>
      <link name="ellipsoid_link">
        <inertial>
          <inertia>
            <ixx>0.068</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.058</iyy>
            <iyz>0</iyz>
            <izz>0.026</izz>
          </inertia>
          <mass>1.0</mass>
        </inertial>
        <collision name="ellipsoid_collision">
          <geometry>
            <ellipsoid>
              <radii>0.2 0.3 0.5</radii>
            </ellipsoid>
          </geometry>
        </collision>
        <visual name="ellipsoid_visual">
          <geometry>
            <ellipsoid>
              <radii>0.2 0.3 0.5</radii>
            </ellipsoid>
          </geometry>
          <material>
            <ambient>1 0 1 1</ambient>
            <diffuse>1 0 1 1</diffuse>
            <specular>1 0 1 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="cone">
      <pose>0 4.5 0.5 0 0 0</pose>
      <link name="cone_link">
        <inertial auto="true">
          <density>1</density>
        </inertial>
        <collision name="cone_collision">
          <geometry>
            <cone>
              <radius>0.5</radius>
              <length>1.0</length>
            </cone>
          </geometry>
        </collision>

        <visual name="cone_visual">
          <geometry>
            <cone>
              <radius>0.5</radius>
              <length>1.0</length>
            </cone>
          </geometry>
          <material>
            <ambient>1 0.47 0 1</ambient>
            <diffuse>1 0.47 0 1</diffuse>
            <specular>1 0.47 0 1</specular>
          </material>
        </visual>
      </link>
    </model>
  </world>
</sdf>

As you could have noticed, even simple world files can have a relatively complex format. The example shapes.sdf, that has only a few simple objects, is difficult to parse visually. For most things, it is easier to use Gazebo itself and limit and direct changes in .sdf files.

Adding or removing things directly on Gazebo is sometimes not repeatable with possible GUI changes across versions. In addition, it is not as natural for a text-based tutorial such as this one. In those scenarios, I will show how to edit the file directly.

This tutorial will limit itself on using default .sdf files and making small modifications. Our interest is to be able obtain and send useful information from Gazebo to ROS.

You will notice in this file some of the most common elements of .sdf. These are not the only elements and this list is not meant to be comprehensive.

• <sdf> is the highest-level element, defining the entire .sdf.

• <world name="world_name"> encloses the elements in this world and gives it a name. This name, rather than the name of the file, will be used when exposing topics and services.

• <scene> has broad elements of the scene, such as background color.

• Entities can include:

  • <light> a source of light

  • <model> a model in the simulation, such as simple shapes or a robot, that can include other information such as <link>, <visual>, and <collision>.

Note

If your application demands it, you will need specialised programs to create 3D models, such as Blender. It won’t be usually manageable to create complicated models directly on Gazebo.

In this example, because we’re using simple shapes supported by Gazebo, they are defined with <geometry> elements.

Gazebo topics and services

Caution

Internal Gazebo topics and services are not the same as ROS2 topics and services.

A Gazebo scene will have a number of internal topics and services. We can interact with them using gz commands. The messages that flow through Gazebo are based on protobuf, not ROS2 IDL.

Let us use an example with sensors. This example is available in the official repository.

Contents of sensors_demo.sdf

<?xml version="1.0" ?>
<!--
  Load several rendering sensors.
-->
<sdf version="1.6">
  <world name="lidar_sensor">
    <physics name="1ms" type="ignored">
      <max_step_size>0.001</max_step_size>
      <real_time_factor>1.0</real_time_factor>
    </physics>
    <plugin
      filename="gz-sim-physics-system"
      name="gz::sim::systems::Physics">
    </plugin>
    <plugin
      filename="gz-sim-sensors-system"
      name="gz::sim::systems::Sensors">
      <render_engine>ogre2</render_engine>
    </plugin>
    <plugin
      filename="gz-sim-user-commands-system"
      name="gz::sim::systems::UserCommands">
    </plugin>
    <plugin
      filename="gz-sim-scene-broadcaster-system"
      name="gz::sim::systems::SceneBroadcaster">
    </plugin>


    <gui fullscreen="0">

      <!-- 3D scene -->
      <plugin filename="MinimalScene" name="3D View">
        <gz-gui>
          <title>3D View</title>
          <property type="bool" key="showTitleBar">false</property>
          <property type="string" key="state">docked</property>
        </gz-gui>

        <engine>ogre2</engine>
        <scene>scene</scene>
        <ambient_light>0.4 0.4 0.4</ambient_light>
        <background_color>0.8 0.8 0.8</background_color>
        <camera_pose>-6 0 6 0 0.5 0</camera_pose>
      </plugin>

      <!-- Plugins that add functionality to the scene -->
      <plugin filename="EntityContextMenuPlugin" name="Entity context menu">
        <gz-gui>
          <property key="state" type="string">floating</property>
          <property key="width" type="double">5</property>
          <property key="height" type="double">5</property>
          <property key="showTitleBar" type="bool">false</property>
        </gz-gui>
      </plugin>
      <plugin filename="GzSceneManager" name="Scene Manager">
        <gz-gui>
          <property key="resizable" type="bool">false</property>
          <property key="width" type="double">5</property>
          <property key="height" type="double">5</property>
          <property key="state" type="string">floating</property>
          <property key="showTitleBar" type="bool">false</property>
        </gz-gui>
      </plugin>
      <plugin filename="InteractiveViewControl" name="Interactive view control">
        <gz-gui>
          <property key="resizable" type="bool">false</property>
          <property key="width" type="double">5</property>
          <property key="height" type="double">5</property>
          <property key="state" type="string">floating</property>
          <property key="showTitleBar" type="bool">false</property>
        </gz-gui>
      </plugin>
      <plugin filename="CameraTracking" name="Camera Tracking">
        <gz-gui>
          <property key="resizable" type="bool">false</property>
          <property key="width" type="double">5</property>
          <property key="height" type="double">5</property>
          <property key="state" type="string">floating</property>
          <property key="showTitleBar" type="bool">false</property>
        </gz-gui>
      </plugin>
      <!-- World control -->
      <plugin filename="WorldControl" name="World control">
        <gz-gui>
          <title>World control</title>
          <property type="bool" key="showTitleBar">false</property>
          <property type="bool" key="resizable">false</property>
          <property type="double" key="height">72</property>
          <property type="double" key="z">1</property>

          <property type="string" key="state">floating</property>
          <anchors target="3D View">
            <line own="left" target="left"/>
            <line own="bottom" target="bottom"/>
          </anchors>
        </gz-gui>

        <play_pause>true</play_pause>
        <step>true</step>
        <start_paused>true</start_paused>
        <use_event>true</use_event>

      </plugin>

      <!-- World statistics -->
      <plugin filename="WorldStats" name="World stats">
        <gz-gui>
          <title>World stats</title>
          <property type="bool" key="showTitleBar">false</property>
          <property type="bool" key="resizable">false</property>
          <property type="double" key="height">110</property>
          <property type="double" key="width">290</property>
          <property type="double" key="z">1</property>

          <property type="string" key="state">floating</property>
          <anchors target="3D View">
            <line own="right" target="right"/>
            <line own="bottom" target="bottom"/>
          </anchors>
        </gz-gui>

        <sim_time>true</sim_time>
        <real_time>true</real_time>
        <real_time_factor>true</real_time_factor>
        <iterations>true</iterations>
      </plugin>

      <!-- Inspector -->
      <plugin filename="ComponentInspector" name="Component inspector">
        <gz-gui>
          <property type="string" key="state">docked</property>
        </gz-gui>
      </plugin>

      <!-- Entity tree -->
      <plugin filename="EntityTree" name="Entity tree">
        <gz-gui>
          <property type="string" key="state">docked</property>
        </gz-gui>
      </plugin>

      <plugin filename="ImageDisplay" name="Image Display">
        <gz-gui>
          <title>RGB camera</title>
          <property key="state" type="string">floating</property>
          <property type="double" key="width">350</property>
          <property type="double" key="height">315</property>
        </gz-gui>
        <topic>camera</topic>
        <topic_picker>false</topic_picker>
      </plugin>
      <plugin filename="ImageDisplay" name="Image Display 2">
        <gz-gui>
          <title>Depth camera</title>
          <property key="state" type="string">floating</property>
          <property type="double" key="width">350</property>
          <property type="double" key="height">315</property>
          <property type="double" key="x">500</property>
        </gz-gui>
        <topic>depth_camera</topic>
        <topic_picker>false</topic_picker>
      </plugin>
      <plugin filename="ImageDisplay" name="Image Display 3">
        <gz-gui>
          <title>RGBD: image</title>
          <property key="state" type="string">floating</property>
          <property type="double" key="width">350</property>
          <property type="double" key="height">315</property>
          <property type="double" key="y">320</property>
        </gz-gui>
        <topic>rgbd_camera/image</topic>
        <topic_picker>false</topic_picker>
      </plugin>
      <plugin filename="ImageDisplay" name="Image Display 3">
        <gz-gui>
          <title>RGBD: depth</title>
          <property key="state" type="string">floating</property>
          <property type="double" key="width">350</property>
          <property type="double" key="height">315</property>
          <property type="double" key="x">500</property>
          <property type="double" key="y">320</property>
        </gz-gui>
        <topic>rgbd_camera/depth_image</topic>
        <topic_picker>false</topic_picker>
      </plugin>
      <plugin filename="ImageDisplay" name="Image Display 5">
        <gz-gui>
          <title>Thermal camera</title>
          <property key="state" type="string">floating</property>
          <property type="double" key="width">350</property>
          <property type="double" key="height">315</property>
          <property type="double" key="x">500</property>
          <property type="double" key="y">640</property>
        </gz-gui>
        <topic>thermal_camera</topic>
        <topic_picker>false</topic_picker>
      </plugin>
    </gui>

    <light type="directional" name="sun">
      <cast_shadows>true</cast_shadows>
      <pose>0 0 10 0 0 0</pose>
      <diffuse>0.8 0.8 0.8 1</diffuse>
      <specular>0.2 0.2 0.2 1</specular>
      <attenuation>
        <range>1000</range>
        <constant>0.9</constant>
        <linear>0.01</linear>
        <quadratic>0.001</quadratic>
      </attenuation>
      <direction>-0.5 0.1 -0.9</direction>
    </light>

    <model name="ground_plane">
      <static>true</static>
      <link name="link">
        <collision name="collision">
          <geometry>
            <!--plane>
              <normal>0 0 1</normal>
              <size>100 100</size>
            </plane-->
            <box>
              <size>20 20 0.1</size>
            </box>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <!--plane>
              <normal>0 0 1</normal>
              <size>100 100</size>
            </plane-->
            <box>
              <size>20 20 0.1</size>
            </box>
          </geometry>
          <material>
            <ambient>0.8 0.8 0.8 1</ambient>
            <diffuse>0.8 0.8 0.8 1</diffuse>
            <specular>0.8 0.8 0.8 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="box">
      <pose>0 -1 0.5 0 0 0</pose>
      <link name="box_link">
        <inertial>
          <inertia>
            <ixx>1</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>1</iyy>
            <iyz>0</iyz>
            <izz>1</izz>
          </inertia>
          <mass>1.0</mass>
        </inertial>
        <collision name="box_collision">
          <geometry>
            <box>
              <size>1 1 1</size>
            </box>
          </geometry>
        </collision>

        <visual name="box_visual">
          <geometry>
            <box>
              <size>1 1 1</size>
            </box>
          </geometry>
          <material>
            <ambient>1 0 0 1</ambient>
            <diffuse>1 0 0 1</diffuse>
            <specular>1 0 0 1</specular>
          </material>
        </visual>
      </link>
    </model>

    <model name="cameras_alone">
      <pose>2.5 0 1.5 0 0.0 3.14</pose>
      <link name="link">
        <pose>0.05 0.05 0.05 0 0 0</pose>
        <inertial>
          <mass>0.1</mass>
          <inertia>
            <ixx>0.000166667</ixx>
            <iyy>0.000166667</iyy>
            <izz>0.000166667</izz>
          </inertia>
        </inertial>
        <collision name="collision">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </visual>
        <sensor name="cameras_alone" type="camera">
          <camera>
            <horizontal_fov>1.047</horizontal_fov>
            <image>
              <width>320</width>
              <height>240</height>
            </image>
            <clip>
              <near>0.1</near>
              <far>100</far>
            </clip>
          </camera>
          <always_on>1</always_on>
          <update_rate>30</update_rate>
          <visualize>true</visualize>
          <topic>camera_alone</topic>
          <enable_metrics>true</enable_metrics>
        </sensor>
        <sensor name="depth_camera1" type="depth_camera">
          <update_rate>10</update_rate>
          <topic>depth_camera</topic>
          <enable_metrics>true</enable_metrics>
          <camera>
            <horizontal_fov>1.05</horizontal_fov>
            <image>
              <width>320</width>
              <height>240</height>
              <format>R_FLOAT32</format>
            </image>
            <clip>
              <near>0.1</near>
              <far>10.0</far>
            </clip>
          </camera>
          </sensor>
      </link>
      <static>true</static>
    </model>

    <model name="camera_with_lidar">
      <pose>4 0 0.5 0 0.0 3.14</pose>
      <link name="link">
        <pose>0.05 0.05 0.05 0 0 0</pose>
        <inertial>
          <mass>0.1</mass>
          <inertia>
            <ixx>0.000166667</ixx>
            <iyy>0.000166667</iyy>
            <izz>0.000166667</izz>
          </inertia>
        </inertial>
        <collision name="collision">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </visual>
        <sensor name="camera" type="camera">
          <camera>
            <horizontal_fov>1.047</horizontal_fov>
            <image>
              <width>320</width>
              <height>240</height>
            </image>
            <clip>
              <near>0.1</near>
              <far>100</far>
            </clip>
          </camera>
          <always_on>1</always_on>
          <update_rate>30</update_rate>
          <visualize>true</visualize>
          <topic>camera</topic>
        </sensor>

        <sensor name='gpu_lidar' type='gpu_lidar'>"
          <topic>lidar</topic>
          <update_rate>10</update_rate>
          <enable_metrics>true</enable_metrics>
          <ray>
            <scan>
              <horizontal>
                <samples>640</samples>
                <resolution>1</resolution>
                <min_angle>-1.396263</min_angle>
                <max_angle>1.396263</max_angle>
              </horizontal>
              <vertical>
                <samples>1</samples>
                <resolution>0.01</resolution>
                <min_angle>0</min_angle>
                <max_angle>0</max_angle>
              </vertical>
            </scan>
            <range>
              <min>0.08</min>
              <max>10.0</max>
              <resolution>0.01</resolution>
            </range>
          </ray>
          <visualize>true</visualize>
        </sensor>
      </link>

      <static>true</static>
    </model>

    <model name="rgbd_camera">
      <pose>5 0 0.5 0 0.0 3.14</pose>
      <link name="link">
        <pose>0.05 0.05 0.05 0 0 0</pose>
        <inertial>
          <mass>0.1</mass>
          <inertia>
            <ixx>0.000166667</ixx>
            <iyy>0.000166667</iyy>
            <izz>0.000166667</izz>
          </inertia>
        </inertial>
        <collision name="collision">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </visual>
        <sensor name="rgbd_camera" type="rgbd_camera">
          <camera>
            <horizontal_fov>1.047</horizontal_fov>
            <image>
              <width>320</width>
              <height>240</height>
            </image>
            <clip>
              <near>0.1</near>
              <far>100</far>
            </clip>
          </camera>
          <always_on>1</always_on>
          <update_rate>30</update_rate>
          <visualize>true</visualize>
          <topic>rgbd_camera</topic>
          <enable_metrics>true</enable_metrics>
        </sensor>
      </link>
    </model>

    <model name="thermal_camera">
      <pose>3 0 0.5 0 0.0 3.14</pose>
      <link name="link">
        <pose>0.05 0.05 0.05 0 0 0</pose>
        <inertial>
          <mass>0.1</mass>
          <inertia>
            <ixx>0.000166667</ixx>
            <iyy>0.000166667</iyy>
            <izz>0.000166667</izz>
          </inertia>
        </inertial>
        <collision name="collision">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </visual>
        <sensor name="thermal_camera" type="thermal_camera">
          <camera>
            <horizontal_fov>1.047</horizontal_fov>
            <image>
              <width>320</width>
              <height>240</height>
            </image>
            <clip>
              <near>0.1</near>
              <far>100</far>
            </clip>
          </camera>
          <always_on>1</always_on>
          <update_rate>30</update_rate>
          <visualize>true</visualize>
          <topic>thermal_camera</topic>
        </sensor>
      </link>
    </model>

    <include>
      <pose>0 1 3 0.0 0.0 1.57</pose>
      <uri>
      https://fuel.gazebosim.org/1.0/OpenRobotics/models/Construction Cone
      </uri>
    </include>

  </world>
</sdf>

To enable physical simulation, including sensor, we can see that a new tag, <plugins> is added. These are paramount to guarantee that sensors will work. Further, they create important topics and services in Gazebo. Here are the plugins active on this file.

    <physics name="1ms" type="ignored">
      <max_step_size>0.001</max_step_size>
      <real_time_factor>1.0</real_time_factor>
    </physics>
    <plugin
      filename="gz-sim-physics-system"
      name="gz::sim::systems::Physics">
    </plugin>
    <plugin
      filename="gz-sim-sensors-system"
      name="gz::sim::systems::Sensors">
      <render_engine>ogre2</render_engine>
    </plugin>
    <plugin
      filename="gz-sim-user-commands-system"
      name="gz::sim::systems::UserCommands">
    </plugin>
    <plugin
      filename="gz-sim-scene-broadcaster-system"
      name="gz::sim::systems::SceneBroadcaster">
    </plugin>

We will now start to interact with Gazebo. For this section, suppose that we have the scene always open with the following command.

Tip

You will see online, very frequently, the command using -v4. For instance, as follows. This allows Gazebo to output many messages to the terminal in which it was opened to help you understand what is happening.

gz sim -v4 sensors_demo.sdf

gz sim sensors_demo.sdf

A frequently used tool to allow us to inspect internal Gazebo topics will be, in another terminal, to run the following command. The -l flag allows us to list Gazebo topics.

gz topic -l

If the correct scene is running on Gazebo, the output should be similar to the following output.

/camera
/camera_alone
/camera_info
/clock
/depth_camera
/depth_camera/performance_metrics
/depth_camera/points
/gazebo/resource_paths
/gui/camera/pose
/gui/currently_tracked
/gui/track
/lidar
/lidar/points
/rgbd_camera/camera_info
/rgbd_camera/depth_image
/rgbd_camera/image
/rgbd_camera/performance_metrics
/rgbd_camera/points
/sensors/marker
/stats
/thermal_camera
/world/lidar_sensor/clock
/world/lidar_sensor/dynamic_pose/info
/world/lidar_sensor/pose/info
/world/lidar_sensor/scene/deletion
/world/lidar_sensor/scene/info
/world/lidar_sensor/state
/world/lidar_sensor/stats
/world/lidar_sensor/light_config
/world/lidar_sensor/material_color

Further information can be obtained about topics, for instance, the type of message that flows through them. We can check what is the message type used in one of the sensors as follows.

gz topic -i --topic /rgbd_camera/image

The output of that command should be similar to the following.

Publishers [Address, Message Type]:
  tcp://172.16.191.128:40679, gz.msgs.Image
Subscribers [Address, Message Type]:
  tcp://172.16.191.128:40229, gz.msgs.Image

Information about services, similarly, can be obtained with the following command.

gz service -l

Resulting in the following output.

Services in sensors_demo.sdf

/camera/set_rate
/camera_alone/set_rate
/depth_camera/set_rate
/gazebo/resource_paths/add
/gazebo/resource_paths/get
/gazebo/resource_paths/resolve
/gazebo/worlds
/gui/camera/view_control
/gui/camera/view_control/reference_visual
/gui/camera/view_control/sensitivity
/gui/follow
/gui/follow/offset
/gui/move_to
/gui/move_to/pose
/lidar/set_rate
/rgbd_camera/set_rate
/sensors/marker
/sensors/marker/list
/sensors/marker_array
/server_control
/thermal_camera/set_rate
/world/lidar_sensor/control
/world/lidar_sensor/control/state
/world/lidar_sensor/create
/world/lidar_sensor/create/blocking
/world/lidar_sensor/create_multiple
/world/lidar_sensor/create_multiple/blocking
/world/lidar_sensor/declare_parameter
/world/lidar_sensor/disable_collision
/world/lidar_sensor/disable_collision/blocking
/world/lidar_sensor/enable_collision
/world/lidar_sensor/enable_collision/blocking
/world/lidar_sensor/entity/system/add
/world/lidar_sensor/generate_world_sdf
/world/lidar_sensor/get_parameter
/world/lidar_sensor/gui/info
/world/lidar_sensor/level/set_performer
/world/lidar_sensor/light_config
/world/lidar_sensor/light_config/blocking
/world/lidar_sensor/list_parameters
/world/lidar_sensor/playback/control
/world/lidar_sensor/remove
/world/lidar_sensor/remove/blocking
/world/lidar_sensor/scene/graph
/world/lidar_sensor/scene/info
/world/lidar_sensor/set_parameter
/world/lidar_sensor/set_physics
/world/lidar_sensor/set_physics/blocking
/world/lidar_sensor/set_pose
/world/lidar_sensor/set_pose/blocking
/world/lidar_sensor/set_pose_vector
/world/lidar_sensor/set_pose_vector/blocking
/world/lidar_sensor/set_spherical_coordinates
/world/lidar_sensor/set_spherical_coordinates/blocking
/world/lidar_sensor/state
/world/lidar_sensor/state_async
/world/lidar_sensor/system/info
/world/lidar_sensor/visual_config
/world/lidar_sensor/visual_config/blocking
/world/lidar_sensor/wheel_slip
/world/lidar_sensor/wheel_slip/blocking

We can also obtain information about each service. For instance, with the command.

gz service -i --service /rgbd_camera/set_rate

Resulting in the following output.

Service providers [Address, Request Message Type, Response Message Type]:
  tcp://172.16.191.128:36013, gz.msgs.Double, gz.msgs.Empty

There are multiple ways to interact with the Gazebo internal topics. This can be, for instance, done through the commandline using similar commands to the ones we have shown so far. Nonetheless, if you have spent so much time learning ROS2, it would be more convenient to find a way to bridge the topics and services from Gazebo and ROS2.

Nonetheless, when some piece of information is not flowing as expected, remember these commands to help troubleshoot.

The package ros_gz_sim

See also

The official repository: gazebosim/ros_gz

The package ros_gz_sim has a few tools allowing us to control Gazebo over ROS2. Namely, the ability to start Gazebo and spawn (add) objects. These might depend on Gazebo topics and services, therefore make sure that the necessary plugins are enabled.

Launching Gazebo

For example, we can launch Gazebo directly from a launch file.

ros2 launch ros_gz_sim gz_sim.launch.py gz_args:=shapes.sdf

In this command, gz_args we add a representation file known to Gazebo. In this case, shapes.sdf. You can specify other scenes.

Spawn models

You can use the following command to spawn models in Gazebo.

Terminal 1: Run Gazebo

ros2 launch ros_gz_sim gz_sim.launch.py gz_args:=shapes.sdf

Terminal 2: Spawn model

ros2 launch ros_gz_sim gz_spawn_model.launch.py world:=shapes file:=$(ros2 pkg prefix --share ros_gz_sim_demos)/models/vehicle/model.sdf entity_name:=my_vehicle x:=5.0 y:=5.0 z:=0.5

As arguments we have the

• model filename

• name for the entity inside Gazebo

• position coordinates of the model

Note

The scene specified in the argument world must be active in Gazebo for the command above to work.

This will add the model, in this case, model.sdf to the scene shapes.sdf. The output on the terminal will be as follows.

[INFO] [launch]: All log files can be found below /home/murilo/.ros/log/2025-11-06-11-19-14-321361-murilo-VMware20-1-14158
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [create-1]: process started with pid [14161]
[create-1] [WARN] [1762427959.367373569] [ros_gz_sim]: Waiting for service [/world/shapes/create] to become available ...
[create-1] [INFO] [1762427959.598035759] [ros_gz_sim]: Entity creation successful.
[INFO] [create-1]: process has finished cleanly [pid 14161]

The package ros_gz_sim_demos

See also

The official repository: gazebosim/ros_gz

This official package has many examples integrating Gazebo and ROS2. It showcases many functionalities that are useful for robotics applications.

You can verify all files usable for Gazebo demos in the following folder.

cd $(ros2 pkg prefix --share ros_gz_sim_demos)
nautilus .

The current file structure is shown in the dropdown below. There are many launch files, rviz configuration files, and a few .sdf models.

The structure of ros_gz_sim_demos.

/opt/ros/jazzy/share/ros_gz_sim_demos
├── cmake
│   ├── ros_gz_sim_demosConfig.cmake
│   └── ros_gz_sim_demosConfig-version.cmake
├── environment
│   ├── ament_prefix_path.dsv
│   ├── ament_prefix_path.sh
│   ├── path.dsv
│   ├── path.sh
│   └── ros_gz_sim_demos.dsv
├── launch
│   ├── air_pressure.launch.py
│   ├── battery.launch.py
│   ├── camera.launch.py
│   ├── depth_camera.launch.py
│   ├── diff_drive.launch.py
│   ├── gpu_lidar_bridge.launch.py
│   ├── gpu_lidar.launch.py
│   ├── image_bridge.launch.py
│   ├── imu.launch.py
│   ├── joint_states.launch.py
│   ├── magnetometer.launch.py
│   ├── navsat_gpsfix.launch.py
│   ├── navsat.launch.py
│   ├── rgbd_camera_bridge.launch.py
│   ├── rgbd_camera.launch.py
│   ├── robot_description_publisher.launch.py
│   ├── sdf_parser.launch.py
│   ├── tf_bridge.launch.py
│   └── triggered_camera.launch.py
├── local_setup.bash
├── local_setup.dsv
├── local_setup.sh
├── local_setup.zsh
├── models
│   ├── cardboard_box
│   │   ├── materials
│   │   │   └── textures
│   │   │       └── cardboard_box.png
│   │   ├── meshes
│   │   │   └── cardboard_box.dae
│   │   ├── model.config
│   │   ├── model.sdf
│   │   └── thumbnails
│   │       ├── 1.png
│   │       ├── 2.png
│   │       ├── 3.png
│   │       ├── 4.png
│   │       └── 5.png
│   ├── double_pendulum_model.sdf
│   ├── rrbot.xacro
│   └── vehicle
│       ├── model.config
│       └── model.sdf
├── package.dsv
├── package.xml
├── rviz
│   ├── camera.rviz
│   ├── depth_camera.rviz
│   ├── diff_drive.rviz
│   ├── gpu_lidar_bridge.rviz
│   ├── gpu_lidar.rviz
│   ├── imu.rviz
│   ├── joint_states.rviz
│   ├── rgbd_camera_bridge.rviz
│   ├── rgbd_camera.rviz
│   ├── robot_description_publisher.rviz
│   ├── tf_bridge.rviz
│   └── vehicle.rviz
└── worlds
    ├── default.sdf
    └── vehicle.sdf

Note

The contents above are not retrieved automatically so they might not represent the latest version of the repository. See gazebosim/ros_gz .

The camera.launch.py demo

We can run this example with the following command.

ros2 launch ros_gz_sim_demos camera.launch.py

This will show Gazebo, with a couple of objects and a camera. The camera view is being rendered by Gazebo. The simulation is started. At the same time, rviz2 is executed. This demo is important because cameras are difficult to simulate otherwise and being able to access them via ROS2 allows you to create powerful image-based robot controllers and planners.

We can take a look at the topics created, while those programs are running, with the following command.

ros2 topic list

This will output the following.

/camera
/camera_info
/clicked_point
/initialpose
/move_base_simple/goal
/parameter_events
/rosout
/tf
/tf_static

The launch file, camera.launch.py, is currently performing the following steps.

• Starting Gazebo with the built-in scene camera_sensor.sdf.

• Running rviz2 with the configuration file camera.rviz.

• Running ros_gz_bridge with the correct parameters to expose the camera sensor from Gazebo to ROS2.

This demo shows the camera simulation results on rviz2 because it’s possibly the most convenient way of showing that the information is correctly flowing through ROS2.

Note

Some unused topics such as /tf are defined in camera.rviz, but don’t worry about those.

Below are the contents of the launch file.

The contents of launch/camera.launch.py

# Copyright 2019 Open Source Robotics Foundation, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import os

from ament_index_python.packages import get_package_share_directory

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.actions import IncludeLaunchDescription
from launch.conditions import IfCondition
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import LaunchConfiguration

from launch_ros.actions import Node


def generate_launch_description():

    pkg_ros_gz_sim_demos = get_package_share_directory('ros_gz_sim_demos')
    pkg_ros_gz_sim = get_package_share_directory('ros_gz_sim')

    gz_sim = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            os.path.join(pkg_ros_gz_sim, 'launch', 'gz_sim.launch.py')),
        launch_arguments={'gz_args': '-r camera_sensor.sdf'}.items(),
    )

    # RViz
    rviz = Node(
        package='rviz2',
        executable='rviz2',
        arguments=['-d', os.path.join(pkg_ros_gz_sim_demos, 'rviz', 'camera.rviz')],
        condition=IfCondition(LaunchConfiguration('rviz'))
    )

    # Bridge
    bridge = Node(
        package='ros_gz_bridge',
        executable='parameter_bridge',
        arguments=['/camera@sensor_msgs/msg/Image@gz.msgs.Image',
                   '/camera_info@sensor_msgs/msg/CameraInfo@gz.msgs.CameraInfo'],
        output='screen'
    )

    return LaunchDescription([
        DeclareLaunchArgument('rviz', default_value='true',
                              description='Open RViz.'),
        gz_sim,
        bridge,
        rviz
    ])

Below are the contents of the rviz file.

The contents of rviz/camera.rviz

Panels:
  - Class: rviz_common/Displays
    Help Height: 0
    Name: Displays
    Property Tree Widget:
      Expanded:
        - /Global Options1
        - /Camera1
        - /Camera1/Status1
        - /Image1
      Splitter Ratio: 0.5
    Tree Height: 557
  - Class: rviz_common/Selection
    Name: Selection
  - Class: rviz_common/Tool Properties
    Expanded:
      - /2D Nav Goal1
      - /Publish Point1
    Name: Tool Properties
    Splitter Ratio: 0.5886790156364441
  - Class: rviz_common/Views
    Expanded:
      - /Current View1
    Name: Views
    Splitter Ratio: 0.5
Visualization Manager:
  Class: ""
  Displays:
    - Alpha: 0.5
      Cell Size: 1
      Class: rviz_default_plugins/Grid
      Color: 160; 160; 164
      Enabled: true
      Line Style:
        Line Width: 0.029999999329447746
        Value: Lines
      Name: Grid
      Normal Cell Count: 0
      Offset:
        X: 0
        Y: 0
        Z: 0
      Plane: XY
      Plane Cell Count: 10
      Reference Frame: <Fixed Frame>
      Value: true
    - Class: rviz_default_plugins/Camera
      Enabled: true
      Image Rendering: background and overlay
      Name: Camera
      Overlay Alpha: 0.5
      Queue Size: 10
      Topic: /camera
      Unreliable: false
      Value: true
      Visibility:
        Grid: true
        Image: true
        Value: true
      Zoom Factor: 1
    - Class: rviz_default_plugins/Image
      Enabled: true
      Max Value: 1
      Median window: 5
      Min Value: 0
      Name: Image
      Normalize Range: true
      Queue Size: 10
      Topic: /camera
      Unreliable: false
      Value: true
  Enabled: true
  Global Options:
    Background Color: 48; 48; 48
    Fixed Frame: camera/link/camera
    Frame Rate: 30
  Name: root
  Tools:
    - Class: rviz_default_plugins/MoveCamera
    - Class: rviz_default_plugins/Select
    - Class: rviz_default_plugins/FocusCamera
    - Class: rviz_default_plugins/Measure
      Line color: 128; 128; 0
    - Class: rviz_default_plugins/SetInitialPose
      Topic: /initialpose
    - Class: rviz_default_plugins/SetGoal
      Topic: /move_base_simple/goal
    - Class: rviz_default_plugins/PublishPoint
      Single click: true
      Topic: /clicked_point
  Transformation:
    Current:
      Class: rviz_default_plugins/TF
  Value: true
  Views:
    Current:
      Class: rviz_default_plugins/Orbit
      Distance: 19.73822784423828
      Enable Stereo Rendering:
        Stereo Eye Separation: 0.05999999865889549
        Stereo Focal Distance: 1
        Swap Stereo Eyes: false
        Value: false
      Focal Point:
        X: 0
        Y: 0
        Z: 0
      Focal Shape Fixed Size: true
      Focal Shape Size: 0.05000000074505806
      Invert Z Axis: false
      Name: Current View
      Near Clip Distance: 0.009999999776482582
      Pitch: 0.7903980016708374
      Target Frame: <Fixed Frame>
      Value: Orbit (rviz)
      Yaw: 0.785398006439209
    Saved: ~
Window Geometry:
  Camera:
    collapsed: false
  Displays:
    collapsed: false
  Height: 702
  Hide Left Dock: false
  Hide Right Dock: false
  Image:
    collapsed: false
  QMainWindow State: 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
  Selection:
    collapsed: false
  Tool Properties:
    collapsed: false
  Views:
    collapsed: false
  Width: 859
  X: 517
  Y: 361

The launch file uses the package ros_gz_bridge, which is used to create the interfaces, for instance topics, between Gazebo and ROS2.

We will see this package in more detail in the following section.

References

The official documentation for Gazebo is overall good. Here are some main topics where this tutorial borrowed from.

• https://gazebosim.org/docs/harmonic/sensors/

• https://gazebosim.org/docs/harmonic/ros2_launch_gazebo/

• https://gazebosim.org/docs/harmonic/ros2_integration/

• https://gazebosim.org/docs/harmonic/ros2_spawn_model/

• https://gazebosim.org/docs/harmonic/ros2_interop/

• https://gazebosim.org/docs/harmonic/ros_gz_project_template_guide/

• gazebosim/ros_gz