Add ignition gazebo support for PX4 Software-In-The-Loop simulations

[Jaeyoung-Lim]

Describe problem solved by this pull request
This commit adds SITL support for ignition gazebo. Ignition gazebo is a replacement for the "classic" gazebo for future applications.

Since PX4 uses gazebo for a lot of integration testing and simulated environments, it makes a lot of sense to integrate into the new ignition gazebo.

Describe your solution
This implementation is a first iteration supporting SITL in the ignition environment.

• a mavlink_interface_plugin was implemented as an interface for HIL_* mavlink messages between px4 and ignition gazebo
• Only a quadrotor is supported in the current implementation

A demonstration of the package is shown in the video below:

Test data / coverage
The dependency that is only needed in the regular environment is ignition edifice. This is the latest LTS release of ignition gazebo. Supported environments include Ubuntu Focal / Ubuntu Bionic

sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'
wget http://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
apt update
apt install ignition-edifice

The simulation can be run as the following

make px4_sitl ignition

Additional context

• The submodule that was added can be found in https://github.com/Auterion/px4-simulation-ignition
• Added ignition gazebo to px4 container: Add ignition edifice for Ubuntu focal simulation environment PX4-containers#303

[BazookaJoe1900]

Few questions:

• Do you plan to migrate the gazebo simulation to 'ignition' version?
• Does it conflicts or complimentary?
• what are the benefits? Current and future?

[Jaeyoung-Lim]

@BazookaJoe1900

Do you plan to migrate the gazebo simulation to 'ignition' version?

This is in fact a migration of the current sitl_gazebo into ignition. IMO, the two are different enough that we cannot support both with the same code base

Does it conflicts or complimentary?

It conflicts with the current gazebo implementation. However, since gazebo is one of the most widely used simulation framework, I think it makes sense to support it as long as OSRF supports classical gazebo

what are the benefits? Current and future?

Also, ignition gazebo does not yet include all the subset of features that gazebo used to support, so doing a hard switch now would leave a lot of use cases left alone. You can check out what features ignition gazebo has in https://ignitionrobotics.org/features

Currently there are no direct benefits for our use case, but some differences to note.

• ignition gazebo uses DART as the physics backend verses ODE in classical gazebo
• ignition gazebo supports OGRE2 for rendering

[TSC21]

do we really want to keep this naming?

[julianoes]

No, that's ugly. 😂

[Jaeyoung-Lim]

Done!