Add Gazebo environment variables to allow access to Gazebo models

gazebo_models.txt

0. First check what is the output of "echo $GAZEBO_MODEL_PATH"

What is the output of "echo $GAZEBO_MODEL_PATH"?

1. Run from command line to grant access to models once:
(Tip: cd to the ros package with roscd, then use pwd command to get the full path)

export GAZEBO_MODEL_PATH=~/simulation_ws/src/logistic_demo_sim/models:$GAZEBO_MODEL_PATH

2. To permanently enable Gazebo to locate gazebo model files (SDF's):
$ echo 'export GAZEBO_MODEL_PATH=$GAZEBO_MODEL_PATH:~/catkin_ws/src/gazebo_package/models' >> ~/.bashrc
$ source ~/.bashrc

2.1. Or open up .bashrc:
sudo gedit ~/.bashrc

2.2. and copy & paste following at the end of .bashrc file:

source /usr/share/gazebo/setup.sh

export GAZEBO_MODEL_PATH=~/gazebo_package/models:${GAZEBO_MODEL_PATH}
export GAZEBO_MODEL_PATH=~/gazebo_package/models_gazebo:${GAZEBO_MODEL_PATH}
export GAZEBO_RESOURCE_PATH=~/gazebo_package/worlds:${GAZEBO_RESOURCE_PATH}


3. Add to package.xml file:

<export>
    <!-- gazebo_ros_paths_plugin automatically adds these to
        GAZEBO_MODEL_PATH when you do this export inside
        the package.xml file. -->
    <!-- gazebo_media_path, gazebo_model_path, gazebo_plugin_path -->    
        
        <!-- The world file can use models like this:
        <uri>model://my_package/models/model_name</uri>
        for sdf models located inside the model directory -->
        <!-- <gazebo_ros gazebo_model_path="${prefix}/.." /> -->
       
        <!-- The world file can use models like this:
        <uri>model://wohnung_no_color</uri>
        requires that all sdf models are located inside the models directory -->
        <gazebo_ros gazebo_model_path="${prefix}/models"/>
       
        <!-- <gazebo_ros gazebo_model_path="${prefix}/worlds"/> -->
  </export>


4. Add Gazebo environment variables to launch file:
GAZEBO_PLUGIN_PATH: plugin search path
GAZEBO_MODEL_PATH: models search path

<launch>
    <env name="GAZEBO_PLUGIN_PATH" value="$(optenv GAZEBO_PLUGIN_PATH):/home/user/simulation_ws/devel/lib"/>
    <env name="GAZEBO_MODEL_PATH" value="$(optenv GAZEBO_MODEL_PATH):/home/user/simulation_ws/src/gazebo_world_plugin/models"/>
    <include file="$(find gazebo_ros)/launch/empty_world.launch">
        <arg name="world_name" value="$(find gazebo_world_plugin)/worlds/test.world"/>
        <arg name="verbose" value="true" />
    </include>
</launch>


5. Add to a bash script file that starts the project:

#!/bin/sh

echo " "
echo "configuring gazebo7 plugin paths"
echo "previous GAZEBO_PLUGIN_PATH=$GAZEBO_PLUGIN_PATH"
SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
echo "script directory $SCRIPT_DIR"

MY_PLUGIN_PATH=$SCRIPT_DIR/../lib
echo "plugin path $MY_PLUGIN_PATH"

export GAZEBO_PLUGIN_PATH=$MY_PLUGIN_PATH:$GAZEBO_PLUGIN_PATH
echo "new GAZEBO_PLUGIN_PATH=$GAZEBO_PLUGIN_PATH"

6. Add two bash script files:
---
start.sh
---
#!/usr/bin/env bash

# Make sure we have correct variables.
source scripts/init.sh

---
init.sh
---

# Sets up ENV variables for Gazebo. This file should be 'source'd, not
# executed (otherwise the ENV variables will not be set in our shell.
PROJECT_HOME=$(echo "$(cd "$(dirname "$1")"; pwd)")

# Variables needed for scripts.
export GAZEBO_MODEL_PATH=$PROJECT_HOME/gazebo/models
export GAZEBO_WORLD_PATH=$PROJECT_HOME/gazebo/worlds
export GAZEBO_PLUGIN_PATH=$PROJECT_HOME/gazebo/build

6. Last ressource

Copy the model folders into the ~/.gazebo/models folder in your local computer.


########
Explanation:

<?xml version="1.0"?>
<launch>
  <env name="GAZEBO_MODEL_PATH" value="$(find my_gazebo_worlds)" />
  <env name="GAZEBO_RESOURCE_PATH" value="$(find my_gazebo_worlds)" />
  <!-- Bring up the gazebo gui and an empty world -->
  <include file="$(find gazebo_ros)/launch/empty_world.launch" >
    <arg name="world_name" value="$(find my_gazebo_worlds)/worlds/myworld.world"/>
  </include>  
</launch>

This will setup the GAZEBO_MODEL_PATH variable and the GAZEBO_RESOURCE_PATH variable.
This means that worlds and models can be shared in a ros package.
It also means that also materials (resource path) can be shared.

#######
Spawn objects from launch file

<launch>
<!--x,y,z = 1.028, -0.11, 0.8  rpy = 0,0,0.43-->
<node name="spawn_toy_block" pkg="gazebo_ros" type="spawn_model" args="-file $(find exmpl_models)/toy_block/toy_block.sdf -sdf -model toy_block -x 0.5 -y -0.35 -z 0.8  -Y 0.43" />
</launch>

######
Final note: clear env variable:
unset GAZEBO_MODEL_PATH