# OctoMap 3D Models with ROS/Gazebo Classic

The [OctoMap library](https://octomap.github.io/) is an open source library for generating volumetric 3D environment models from sensor data.
This model data can then be used by a drone for navigation and obstacle avoidance.

This guide covers how to use _OctoMap_ with the [Gazebo Classic](../sim_gazebo_classic/index.md) [Rotors Simulator](https://github.com/ethz-asl/rotors_simulator/wiki/RotorS-Simulator) and ROS.

## 安装

The installation requires ROS, [Gazebo Classic](../sim_gazebo_classic/index.md) and the Rotors Simulator plugin.
Follow the [Rotors Simulator instructions](https://github.com/ethz-asl/rotors_simulator) to install.

Next, install the _OctoMap_ library:

```sh
sudo apt-get install ros-indigo-octomap ros-indigo-octomap-mapping
rosdep install octomap_mapping
rosmake octomap_mapping
```

Now, open `~/catkin_ws/src/rotors_simulator/rotors_gazebo/CMakeLists.txt` and add the following lines to the bottom of the file:

```sh
find_package(octomap REQUIRED)
include_directories(${OCTOMAP_INCLUDE_DIRS})
link_libraries(${OCTOMAP_LIBRARIES})
```

Open `~/catkin_ws/src/rotors_simulator/rotors_gazebo/package.xml` and add the following lines:

```xml
<build_depend>octomap</build_depend>
<run_depend>octomap</run_depend>
```

Run the following two lines:

:::info
The first line changes your default shell editor to _gedit_. This is recommended for users who have little experience with _vim_ (the default editor), but can otherwise be omitted.
:::

```sh
export EDITOR='gedit'
rosed octomap_server octomap_tracking_server.launch
```

and change the two following lines:

```xml
<param name="frame_id" type="string" value="map" />
...
<!--remap from="cloud_in" to="/rgbdslam/batch_clouds" /-->
```

to:

```xml
<param name="frame_id" type="string" value="world" />
...
<remap from="cloud_in" to="/firefly/vi_sensor/camera_depth/depth/points" />
```

## Running the Simulation

Run the following three lines in _separate_ terminal windows.
This opens up [Gazebo Classic](../sim_gazebo_classic/index.md), _Rviz_ and an octomap server.

```sh
roslaunch rotors_gazebo mav_hovering_example_with_vi_sensor.launch  mav_name:=firefly
rviz
roslaunch octomap_server octomap_tracking_server.launch
```

In _Rviz_, change the field 'Fixed Frame' from 'map' to 'world' in the top left of the window.
Now click the add button in the bottom left and select MarkerArray. Then double click the MarkerArray and change 'Marker Topic' from `/free_cells_vis_array` to `/occupied_cells_vis_array`.

Now you should see a part of the floor.

In the _Gazebo Classic_ window, insert a cube in front of the red rotors and you should see it in _Rviz_.

![OctoMap Example in Gazebo](../../assets/simulation/gazebo_classic/octomap.png)