Unity3D Gameplay Framework
All objects spawned in a Unity scene are
Behaviours. For local games we work with
MonoBehaviours and for networking games Unity provides us
NetworkBehaviours. Aside from those there aren’t many abstractions where Unity supports us. I came to the conclusion that great gameplay support should be a feature that ships with the engine, finding myself abandoning projects because it doesn’t.
I’ve worked with Unreal’s Gameplay Framework which I really like and therefore want to improve Unity’s gameplay layer by adding some of the things I have learned from UE4 (Unreal Engine 4). However, the existing
Behaviour code base cannot be removed as it lies at the heart of the Unity Engine.
|Player||A player is a real human. Note that AIs (Bots) are not players.|
|Participant||Players and AIs can become participants when they request to join a game. Participants are taking part in the game and can interact with the world. They can have a huge imapact on the outcome of the game. A player spectator that is not able to interact with the world is not a participant for example.|
|Authority||The authority can either be a local client, a remote client (Host) or a server. A networking game has many actions that require to be authorized before they can happen. Win/Loose conditions are usually evaluated by the authority to prevent cheating for example.|
The Gameplay Framework Classes
The Gameplay Framework consist of a few classes that help to structure gameplay logic.
Game class is a Singleton that provides general interaction with the game.
Controllers join the
Game to become participants for example.
GameMode only exists on the authority. The authority’s
Game instance contains the only
GameMode across all participants. The
GameMode constantly evaluates the
GameState for new events that require authorization. It checks win/loose conditions as a common example.
Games across all participants contain a single
GameState that is synchronized over the network. As the name suggests, this class contains the state of the game. However, not all information about the game must be stored in this class. Only data that must be autorized is required to be available in the
GameState contains a collection of
ParticipantStates. They contain the information of a participant that requires to be authorized. All participants have a
Controller represents the will of a player or an AI. It can possess a single pawn at the time and/or become a participant by requesting a join.
PlayerController is a controller that represents the will of a player.
AIController is a controller that represent artificial intelligence.
IPawn is an entity that can become possessed by a single
Controller at a time. When possessed, a pawn follows the instructions of its
IPawns that are used for local play. They inherit from
IPawns that are used for network play. They inherit from
NetworkBehaviour and are currently not implemented due to a focus on local play for a first version of the Gameplay Framework.
PlayerManagers are associated by
PlayerControllers and handle the interaction between the game and the players.
AIControllers do not require
PlayerManagers because an AI doesn’t require visual feedback.
PlayerInputManager reads the input from the input devices of its player and prepares the information for its
PlayerController. It does not interpret the input but is allowed to make device specific corrections such as applying a deadzone to an analogue stick.
PlayerCameraManagers are the cameramen in a game. Their main job is to position and rotate the camera correctly as well as performing any post-processing on the rendered image.
PlayerHUDManager is responsible to display a player’s HUD (Heads Up Display).