Unity and Python communicate by sending protobuf messages to and from each other. You can create custom protobuf messages if you want to exchange structured data beyond what is included by default.
Assume the ml-agents repository is checked out to a folder named $MLAGENTS_ROOT. Whenever you change the fields of a custom message, you must run `$MLAGENTS_ROOT/protobuf-definitions/make.bat` to create C# and Python files corresponding to the new message. Follow the directions in that file for guidance. After running it, reinstall the Python package by running `pip install $MLAGENTS_ROOT/ml-agents` and make sure your Unity project is using the newly-generated version of `$MLAGENTS_ROOT/UnitySDK`.
Assume the ml-agents repository is checked out to a folder named $MLAGENTS_ROOT. Whenever you change the fields of a custom message, you must run `$MLAGENTS_ROOT/protobuf-definitions/make.bat` to create C# and Python files corresponding to the new message. Follow the directions in [this file](../protobuf-definitions/README.md) for guidance. After running it, reinstall the Python package by running `pip install $MLAGENTS_ROOT/ml-agents` and make sure your Unity project is using the newly-generated version of `$MLAGENTS_ROOT/UnitySDK`.
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