Pinball

Pinball is an environment written on Godot for testing artificial agents.

Entities

RandomForce:
      angles: [phi1, phi2, ...]
      strength: m
      reward: r
      terminal: is_terminal

When ball enters ring area, RandomFroce uniformly choses a direction from angles and applies impluse of magnitude m.

Attractor:
      strength: m
      frequency: f
      reward: r
      terminal: is_terminal

When ball enters ring area, Attractor slowes down the ball and attracts to its center with frequency f.

Both entities have fields:

• reward - r is amount of reward that agent gets by entering the area
• terminal - if is_terminal==true, ball resets the environment by entering the area

Control

• Ctrl+S - open or save confgiuration
• Ctrl+R - reset ball to initial position
• Left/Right arrow - change direction of initial impulse
• Up/Down arrow - change magnitude of initial impulse
• Space - apply initial impulse to ball

Saving new configuration

1. Add new RandomForce and Attractor objects, position and edit them as needed in Godot editor.
2. Run game in debug mode, open settings (Ctrl+S) and enter new config path, click "OK" button.

Python environment

To use the environment in Python programms you can install Python module python_env/pinball.py using python_env/setup.py.

Control of the environment is through Pinball class:

• obs() - returns a tuple: (image observation array, reward, terminal state flag)
• act([phi float, m float]) - apply impulse with direction phi in radians and magnitude m
• step() - do one simulation step if run with --sync=true flag
• reset(position=None) - return ball to initial position and zero velocity, if position is not specified, it uses initial position from config file

For more detailed API see the source code.

To run the environment through Python you need to compile an executable file of the environment through Godot editor. The executable has several useful flags:

• --config=config_path specify wich configuration you would like to run with
• --host=ip_addr and --port=port specify ip address and port of the environment that will be used for TCP connection between Python and Godot parts.
• --disable-render-loop and --no-window are useful for a headless run.
• --fixed-fps breaks real-time synchronization of physics and render, useful for headless rendering.
• --sync=true/false if true, simulation is paused until the next frame is requested by Python environment.
• --seed=seed setup seed to reproduce simulations.

Related work

Code realisation of interaction between Godot and Python parts of the environment is mostly inspired by this repository.