Category: Gazebo

Gazebo classic material colors not working in Gazebo Ignition

Hi everyone,

I’m doing a few tutorials to simulate a lidar based navigation system and I’ve hit a few issues when trying to use Gazebo classic features in Gazebo Ignition.

A recent one is that Gazebo Ignition was ignoring the material colours that I’d specified in my urdf. This is an example of what was working in Gazebo classic:

    <gazebo reference="left_wheel">
        <material>Gazebo/Blue</material>
    </gazebo>

This Github issue revealed the following format that can be used instead:

     <gazebo reference="chassis">
        <visual>
            <material>
                <ambient>0 0 1 1</ambient>
                <diffuse>0 0 1 1</diffuse>
                <specular>0 0 1 1</specular>
            </material>
        </visual>
    </gazebo>

Once updated, Gazebo ignition finally started rendering my material colors:

Gazebo Classic to Gazebo Ignition Diff Drive Conversion

Hi everyone,

I’m currently following some ros2 tutorials for simulating a diff drive robot in Gazebo Classic. I’m using Gazebo Ignition and unfortunately the definitions aren’t interchangeable.

Just in case anyone else hits the same issue, this is the definition I ended up using instead:

        <plugin
            filename="libignition-gazebo-diff-drive-system.so"
            name="ignition::gazebo::systems::DiffDrive"
        >
            <!-- Wheel info: https://youtu.be/IjFcr5r0nMs?t=876 -->
            <left_joint>left_wheel_joint</left_joint>
            <right_joint>right_wheel_joint</right_joint>
            <wheel_separation>0.35</wheel_separation>
            <wheel_diameter>0.1</wheel_diameter>

            <!-- Limits -->
            <max_wheel_torque>200</max_wheel_torque>
            <max_wheel_acceleration>10.0</max_wheel_acceleration>

            <!-- Output -->
            <odometry_frame>odom</odometry_frame>
            <robot_base_frame>base_link</robot_base_frame>

            <publish_odom>true</publish_odom>
            <publish_odom_tf>true</publish_odom_tf>
            <publish_wheel_tf>true</publish_wheel_tf>

        </plugin>

The following links were pretty helpful when it came to tracking down the differences:
– https://github.com/chapulina/dolly/issues/28
– https://github.com/gazebosim/gz-sim/blob/main/examples/worlds/visualize_lidar.sd

Spawn entity timeout in Gazebo from Ros2

Hi everyone,

I’m currently following a tutorial to simulate a fairly basic lidar robot with ROS2 and Gazebo: https://www.youtube.com/watch?v=laWn7_cj434. Unfortunately, there have been a few updates since the tutorial was created and a number of the commands don’t map 1:1 (no copy and paste).

While trying to create a launch file I ran into the following error:

[create-3] [ERROR] [1668289712.483268807] [ros_gz_sim]: Request to create entity from service [/world/deafult/create] timed out.

This was the relevant line in the launch file:

# Run the spawner node from the gazebo_ros package. The entity name doesn't really matter if you only have a single robot.
spawn_entity = Node(package='ros_ign_gazebo', executable='create',
arguments=[
'-world', 'deafult',
'-topic', 'robot_description',
'-entity', 'my_bot'],
output='screen')

The issue causing it to hang is that the world doesn’t exist. In my case, it’s because of a typo. However, if you’ve defined a world that you haven’t created yet it will result in the same error.