ml-agents/docs/Getting-Started-with-Balance-Ball.md

Getting Started with the Balance Ball Example

This tutorial will walk through the end-to-end process of installing Unity Agents, building an example environment, training an agent in it, and finally embedding the trained model into the Unity environment.

Unity ML Agents contains a number of example environments which can be used as templates for new environments, or as ways to test a new ML algorithm to ensure it is functioning correctly.

In this walkthrough we will be using the 3D Balance Ball environment. The environment contains a number of platforms and balls. Platforms can act to keep the ball up by rotating either horizontally or vertically. Each platform is an agent which is rewarded the longer it can keep a ball balanced on it, and provided a negative reward for dropping the ball. The goal of the training process is to have the platforms learn to never drop the ball.

Let's get started!

Installation

In order to install and set-up the Python and Unity environments, see the instructions here.

Building Unity Environment

Launch the Unity Editor, and log in, if necessary.

1. Open the unity-environment folder using the Unity editor. (If this is not first time running Unity, you'll be able to skip most of these immediate steps, choose directly from the list of recently opened projects)
   • On the initial dialog, choose Open on the top options
   • On the file dialog, choose unity-environment and click Open (It is safe to ignore any warning message about non-matching editor installation)
   • Once the project is open, on the Project panel (bottom of the tool), navigate to the folder Assets/ML-Agents/Examples/3DBall/
   • Double-click the Scene icon (Unity logo) to load all environment assets
2. Go to Edit -> Project Settings -> Player
   • Ensure that Resolution and Presentation -> Run in Background is Checked.
   • Ensure that Resolution and Presentation -> Display Resolution Dialog is set to Disabled.
3. Expand the Ball3DAcademy GameObject and locate its child object Ball3DBrain within the Scene hierarchy in the editor. Ensure Type of Brain for this object is set to External.
4. File -> Build Settings
5. Choose your target platform:
   • (optional) Select “Developer Build” to log debug messages.
6. Click Build:
   • Save environment binary to the python sub-directory of the cloned repository (you may need to click on the down arrow on the file chooser to be able to select that folder)

Training the Brain with Reinforcement Learning

Testing Python API

To launch jupyter, run in the command line:

jupyter notebook

Then navigate to localhost:8888 to access the notebooks. If you're new to jupyter, check out the quick start guide before you continue.

To ensure that your environment and the Python API work as expected, you can use the python/Basics Jupyter notebook. This notebook contains a simple walkthrough of the functionality of the API. Within Basics, be sure to set env_name to the name of the environment file you built earlier.

Training with PPO

In order to train an agent to correctly balance the ball, we will use a Reinforcement Learning algorithm called Proximal Policy Optimization (PPO). This is a method that has been shown to be safe, efficient, and more general purpose than many other RL algorithms, as such we have chosen it as the example algorithm for use with ML Agents. For more information on PPO, OpenAI has a recent blog post explaining it.

In order to train the agents within the Ball Balance environment:

1. Open python/PPO.ipynb notebook from Jupyter.
2. Set env_name to whatever you named your environment file.
3. (optional) Set run_path directory to your choice.
4. Run all cells of notebook except for final.

Observing Training Progress

In order to observe the training process in more detail, you can use Tensorboard. In your command line, run :

tensorboard --logdir=summaries

Then navigate to localhost:6006.

From Tensorboard, you will see the summary statistics of six variables:

• Cumulative Reward - The mean cumulative episode reward over all agents. Should increase during a successful training session.
• Value Loss - The mean loss of the value function update. Correlates to how well the model is able to predict the value of each state. This should decrease during a succesful training session.
• Policy Loss - The mean loss of the policy function update. Correlates to how much the policy (process for deciding actions) is changing. The magnitude of this should decrease during a succesful training session.
• Episode Length - The mean length of each episode in the environment for all agents.
• Value Estimates - The mean value estimate for all states visited by the agent. Should increase during a successful training session.
• Policy Entropy - How random the decisions of the model are. Should slowly decrease during a successful training process. If it decreases too quickly, the beta hyperparameter should be increased.

Embedding Trained Brain into Unity Environment [Experimental]

Once the training process displays an average reward of ~75 or greater, and there has been a recently saved model (denoted by the Saved Model message) you can choose to stop the training process by stopping the cell execution. Once this is done, you now have a trained TensorFlow model. You must now convert the saved model to a Unity-ready format which can be embedded directly into the Unity project by following the steps below.

Setting up TensorFlowSharp Support

Because TensorFlowSharp support is still experimental, it is disabled by default. In order to enable it, you must follow these steps. Please note that the Internal Brain mode will only be available once completing these steps.

1. Make sure you are using Unity 2017.1 or newer.
2. Make sure the TensorFlowSharp plugin is in your Asset folder. A Plugins folder which includes TF# can be downloaded here.
3. Go to Edit -> Project Settings -> Player
4. For each of the platforms you target (PC, Mac and Linux Standalone, iOS or Android):
   1. Go into Other Settings.
   2. Select Scripting Runtime Version to Experimental (.NET 4.6 Equivalent)
   3. In Scripting Defined Symbols, add the flag ENABLE_TENSORFLOW
5. Restart the Unity Editor.

Embedding the trained model into Unity

1. Run the final cell of the notebook under "Export the trained TensorFlow graph" to produce an <env_name >.bytes file.
2. Move <env_name>.bytes from python/models/... into unity-environment/Assets/ML-Agents/Examples/3DBall/TFModels/.
3. Open the Unity Editor, and select the 3DBall scene as described above.
4. Select the 3DBallBrain object from the Scene hierarchy.
5. Change the Type of Brain to Internal.
6. Drag the <env_name>.bytes file from the Project window of the Editor to the Graph Model placeholder in the 3DBallBrain inspector window.
7. Set the Graph Placeholder size to 1 (Note that step 7 8 are done because 3DBall is a continuous control environment, and the TensorFlow model requires a noise parameter to decide actions. In cases with discrete control, epsilon is not needed).
8. Add a placeholder called epsilon with a type of floating point and a range of values from 0 to 0.
9. Press the Play button at the top of the editor.

If you followed these steps correctly, you should now see the trained model being used to control the behavior of the balance ball within the Editor itself. From here you can re-build the Unity binary, and run it standalone with your agent's new learned behavior built right in.