include model in world 2023

edit

Figured it out. Here's the process:

$ ign gazebo --version
Ignition Gazebo, version 6.14.0
Copyright (C) 2018 Open Source Robotics Foundation.
Released under the Apache 2.0 License.

ROS2 - Humble. Using fire_station download from https://github.com/osrf/gazebo_models... which has a directory structure like this:

fire_station
--materials
--meshes
--model.config
--model.sdf

Add to .bashrc:

export IGN_GAZEBO_RESOURCE_PATH=<full path to your models directory>

in the launch.py file:

 robot_state_publisher = Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        name='robot_state_publisher',
        output='both',
        parameters=[{
                'robot_description':Command(['xacro',' ', robot_description_file]),
                'use_sim_time': True
            }],
    )

    spawn = Node(
            package='ros_gz_sim', 
            executable='create',
            arguments=[
            '-name', 'mybot',
            '-topic', '/robot_description'],
            output='screen'
        )

        gazebo = ExecuteProcess(
            cmd=['ign', 'gazebo', world_sdf_file],
            output='screen'
        )
    ...

         return LaunchDescription([
             gazebo,
             spawn,
             ... others like starting rviz, joint_state_publisher_gui, ros_gz_bridge etc.
          ])

and in world_sdf_file:

<?xml version='1.0' encoding='ASCII'?>
<sdf version='1.6'>
  <world name='world_demo'>
...
<include>
      <uri>
        model://fire_station
      </uri>
    </include>
...
 </world>
</sdf>