Physics engines

Gazebo supports choosing what physics engine to use at runtime. This is made possible by Gazebo Physics' abstraction layer.

Gazebo uses the DART physics engine by default.

Downstream developers may also integrate other physics engines by creating new Gazebo Physics engine plugins. See Gazebo Physics's tutorials to learn how to integrate a new engine.

How Gazebo finds engines

Gazebo automatically looks for all physics engine plugins that are installed with Gazebo Physics. At the moment, the primary implementation is DART (gz-physics-dartsim-plugin). There is also preliminary support for Bullet (gz-physics-bullet-plugin) and the Bullet Featherstone implementation (gz-physics-bullet-featherstone-plugin)

If you've created a custom engine plugin, you can tell Gazebo where to find it by setting the GZ_SIM_PHYSICS_ENGINE_PATH environment variable to the directory where the plugin's shared library can be found.

For example, if you've created the following physics engine shared library:

# Linux
/home/physics_engines/libCustomEngine.so
# Windows
C:\Users\Robot\physics_engines\CustomEngine.dll

You should set the variable as follows:

# Linux
export GZ_SIM_PHYSICS_ENGINE_PATH=/home/physics_engines
# Windows
set GZ_SIM_PHYSICS_ENGINE_PATH=C:\Users\Robot\physics_engines

If you have several libraries installed in different paths, you can add more paths, for example:

# Linux, separate with :
export GZ_SIM_PHYSICS_ENGINE_PATH=/home/physics_engines:/home/more_engines
# Windows, separate with ;
set GZ_SIM_PHYSICS_ENGINE_PATH=C:\Users\Robot\physics_engines;C:\MoreEngines

Tell Gazebo what engine to load

There are a few different ways of telling Gazebo which engine to load.

For any method, you should provide the name of your plugin's shared library, but the lib prefix and the file extension are optional. So in this example, the file is libCustomEngine.so but it's enough to set CustomEngine. That is also prefered to support multiple operating systems.

From SDF

You can tell Gazebo what engine to load from the SDF world file by giving the shared library name to the Physics plugin tag.

For the example above, you can load it like this:

<plugin
  filename="gz-sim-physics-system"
  name="gz::sim::systems::Physics">
  <engine>
    <filename>CustomEngine</filename>
  </engine>
</plugin>

From the command line

Alternatively, you can choose a plugin from the command line using the --physics-engine option, for example:

gz sim --physics-engine CustomEngine

To use an existing alternative engine (e.g. Bullet Featherstone)

gz sim --physics-engine gz-physics-bullet-featherstone-plugin

From C++ API

All features available through the command line are also available through gz::sim::ServerConfig. When instantiating a server programmatically, a physics engine can be passed to the constructor, for example:

gz::sim::ServerConfig serverConfig;
serverConfig.SetPhysicsEngine("CustomEngine");
 
gz::sim::Server server(serverConfig);

Engine configuration

Gazebo supports the following physics engine configurations through SDF. These options are available to all physics engines, but not all engines may support them. The default physics engine, DART, supports all these options.

• //physics/dart/collision_detector
  • Options supported by DART: ode (default), bullet, fcl, dart.
• //physics/dart/solver/solver_type
  • Options supported by DART: dantzig (default), pgs

Troubleshooting

‍Failed to find plugin [libCustomEngine.so]. Have you checked the GZ_SIM_PHYSICS_ENGINE_PATH environment variable?

Gazebo can't find out where libCustomEngine.so or CustomEngine.dll is located.

If that's an engine you believe should be installed with Gazebo Physics, check if the relevant plugin is installed.

If that's a 3rd party engine, find where the .so or .dll file is installed and add that path to the environment variable as described above.

‍Unable to load the [/home/physics_engines/libCustomEngine.so] library.

There was some problem loading that file. Check that it exists, that you have permissions to access it, and that it's acually a physics engine plugin.

‍No physics plugins implementing required interface found in library [/home/physics_engines/libCustomEngine.so]

The library was found but none of the plugins in the library implement the required interface to be considered a physics plugin.

‍No plugins with all required features found in library [/home/physics_engines/libCustomEngine.so]

This means that there are plugins on that library, but none of them satisfies the minimum requirement of features needed to run a Gazebo simulation. Be sure to implement all the necessary features.

‍Failed to load a valid physics engine from [/home/physics_engines/libCustomEngine.so]

Some engines were found in that library, but none of them could be loaded. Check that the the engines implement all the necessary features.