Lyra Game Phase Subsystem

The Lyra Game Phase Subsystem manages Lyra’s game phases using Gameplay Tags in a nested manner, which allows parent and child phases to be active at the same time, but not sibling phases.

Example: Game.Playing and Game.Playing.WarmUp can coexist, but Game.Playing and Game.ShowingScore cannot.

When a new phase is started, any active phases that are not ancestors will be ended.

Example: if Game.Playing and Game.Playing.CaptureTheFlag are active when Game.Playing.PostGame is started, Game.Playing will remain active, while Game.Playing.CaptureTheFlag will end.

Above description courtesy of excellent C++ comments.

Debugging Tips

• Enable LogLyraGamePhase logging

Lyra Game Phase Ability

Each Game Phase is represented by a Gameplay Ability. The base C++ class is ULyraGamePhaseAbility.

You must assign a Game Phase Tag, which is a Gameplay Tag that represents this phase, for example Game.Playing. This tag determines which other abilities get cancelled when this phase begins.

When the ability is activated, it executes ULyraGamePhaseSubsystem🡒OnBeginPhase just before it actually activates. This causes previous phases to end as needed just before the new phase activates, based on their Game Phase Tag.

When the ability is ended, it executes ULyraGamePhaseSubsystem🡒OnEndPhase just before ending.

Phase Transitions

To transition to a particular game phase, call ULyraGamePhaseSubsystem🡒StartPhase and pass it the Lyra Game Phase Ability representing the game phase you wish to start.

StartPhase will grant the game phase ability to the Game State’s Ability System Component and activate it.

For example in Lyra’s ShooterCore, the B_ShooterGame_Elimination Experience Definition injects a B_TeamDeathMatchScoring component into the Game State. Amongst other things, that game state component hooks into BeginPlay, then waits for the Experience to load and finally starts the Phase_Warmup game phase.

You can optionally specify a callback to be executed when the phase ends.

When the Phase_Warmup phase is activated, it does the necessary stuff to begin the period of waiting for other players to join, etc. It then transitions to Phase_Playing when needed.

The general idea is that each Game Phase Ability handles transitioning from one phase to the next as appropriate. The Game State itself determines which phase is started when the game starts (as configured by the Lyra Experience via component injection).