git_ws/MPC/launch/gazebo_launch/elevator_world.launch

<?xml version="1.0"?>
<launch>

  <!-- these are the arguments you can pass this launch file, for example paused:=true -->
  <arg name="paused" default="false"/>
  <arg name="use_sim_time" default="true"/>
  <arg name="extra_gazebo_args" default=""/>
  <arg name="gui" default="true"/>
  <arg name="recording" default="false"/>
  <!-- Note that 'headless' is currently non-functional.  See gazebo_ros_pkgs issue #491 (-r arg does not disable
       rendering, but instead enables recording). The arg definition has been left here to prevent breaking downstream
       launch files, but it does nothing. -->
  <arg name="headless" default="false"/>
  <arg name="debug" default="false"/>
  <arg name="physics" default="ode"/>
  <arg name="verbose" default="true"/>
  <arg name="output" default="screen"/>
  <arg name="world_name" default="worlds/elevator_ros.world"/> <!-- Note: the world_name is with respect to GAZEBO_RESOURCE_PATH environmental variable -->

  <!-- set use_sim_time flag -->
  <group if="$(arg use_sim_time)">
    <param name="/use_sim_time" value="true" />
  </group>

  <!-- set command arguments -->
  <arg unless="$(arg paused)" name="command_arg1" value=""/>
  <arg     if="$(arg paused)" name="command_arg1" value="-u"/>
  <arg unless="$(arg recording)" name="command_arg2" value=""/>
  <arg     if="$(arg recording)" name="command_arg2" value="-r"/>
  <arg unless="$(arg verbose)" name="command_arg3" value=""/>
  <arg     if="$(arg verbose)" name="command_arg3" value="--verbose"/>
  <arg unless="$(arg debug)" name="script_type" value="gzserver"/>
  <arg     if="$(arg debug)" name="script_type" value="debug"/>

  <!-- start gazebo server-->
  <node name="gazebo" pkg="gazebo_ros" type="$(arg script_type)" respawn="false" output="$(arg output)"
  args="$(arg command_arg1) $(arg command_arg2) $(arg command_arg3) -e $(arg physics) $(arg extra_gazebo_args) $(arg world_name)" />

  <!-- start gazebo client -->
  <group if="$(arg gui)">
    <node name="gazebo_gui" pkg="gazebo_ros" type="gzclient" respawn="false" output="$(arg output)"/>
  </group>

</launch>