C++ refactoring roadmap

[diegoferigo]

In issue #95 I proposed a new way to communicate with Ignition Gazebo. The current architecture of the bindings (mainly GazeboWrapper and IgnitionRobot classes) have been developed over time after many attempts to find a working solution. Though, they are not optimal and now that we have a deeper knowledge of the Ignition Gazebo architecture maybe we can do better.

In the past few days I prototyped new classes inspired by upstream resources such as ignition::gazebo::Model. I like the initial result, and I would like to move this idea forward.

This task is not trivial. However, is mainly a copy-and-paste of existing code, in other words, a refactoring. Here below a recap of the planned activities:

• Use the gympp namespace only for the C++ implementation of OpenAI Gym. This was the earliest attempt of our activities, and then we shifted the focus more towards Python. Though, I don't feel like to delete those files yet. All those resources should go in a separated folder. Split all gympp resources to a separated folder #157
• Design and implement the new bindings (with the long term plan to convert them to interfaces). ScenarI/O: SCENe interfAces for Robot Input / Output - New Ignition Gazebo ECM APIs #158
• Move the current plugins to the cpp folder and update them to work with the new Scenario APIs. Move and update Ignition plugins to work with ScenarI/O #161
• Refactor GazeboWrapper. Refactor GazeboSimulator class #163
• Split gympp and scenario bindings. Improve CMake project and SWIG bindings #165
• Rethink how to insert C++ controller in a simulation. Likely Python agents run slower than the simulator, and the only way to decouple the controller (PID, computed torque, etc) is to make them standalone Systems. Custom controllers: base interfaces, plugins, and fixed-base Computed Torque example #167
• Add new fixed-base computed torque controller. Custom controllers: base interfaces, plugins, and fixed-base Computed Torque example #167
• Remove the C++ gympp::Robot interface and IgnitionRobot class and update GazeboRuntime to use the new bindings. Update Python package with new ScenarI/O APIs #176
• Reach feature parity

cc @traversaro @paolo-viceconte @raffaello-camoriano

[diegoferigo]

Closed via #185