Game.Simulation.BirthSystem

Assembly: Assembly-CSharp
Namespace: Game.Simulation

Type: class

Base: GameSystemBase

Summary:
BirthSystem is a simulation system responsible for evaluating and spawning citizen births each simulation update. It schedules a parallel IJobChunk (CheckBirthJob) that iterates adult citizens, checks household composition and housing, computes birth probability using CitizenParametersData (including student adjustments and adult-female bonus), and spawns baby citizen entities using available citizen prefabs/archetypes. It uses an EndFrameBarrier's EntityCommandBuffer to create entities safely, reports birth statistics to CityStatisticsSystem, and keeps lightweight debug counters (NativeCounter / NativeValue) for births. A small SumBirthJob copies the native counter into a debug-accessible value. The class wires required queries for citizen prefabs and citizen parameter singletons and requires those queries for updating.

Fields

public static readonly int kUpdatesPerDay
This constant (value 16) defines how many update ticks are considered a "day" for birth probability normalization.
private EndFrameBarrier m_EndFrameBarrier
Reference to EndFrameBarrier system used to create an EntityCommandBuffer for safe entity creation at end of frame.
private SimulationSystem m_SimulationSystem
Reference to the SimulationSystem; used to compute update frame index via SimulationUtils.
private CityStatisticsSystem m_CityStatisticsSystem
Reference to CityStatisticsSystem used to enqueue birth statistics events.
private TriggerSystem m_TriggerSystem
Reference to TriggerSystem; the system adds an action buffer writer dependency for jobs.
[DebugWatchValue] private NativeValue<int> m_DebugBirth
NativeValue exposing the counted number of births (copied by SumBirthJob) for debugging/watch purposes.
private NativeCounter m_DebugBirthCounter
NativeCounter used by CheckBirthJob to increment when a spawn occurs; aggregated by SumBirthJob.
private EntityQuery m_CitizenQuery
EntityQuery selecting citizens to evaluate for potential births (reads Citizen, HouseholdMember, UpdateFrame, CurrentBuilding; excludes Deleted/Temp).
private EntityQuery m_CitizenPrefabQuery
Query used to collect citizen prefabs and archetype data (prefabs to instantiate when spawning babies).
private EntityQuery m_CitizenParametersQuery
Query used to read the singleton CitizenParametersData that contains base birth rate, student adjustment, adult female bonus, etc.
public int m_BirthChance
Public integer field present in the class (default 20). Note: the shown implementation does not reference this field for the birth calculations — births are driven by CitizenParametersData and random rolls in CheckBirthJob.
private TypeHandle __TypeHandle
Internal structure caching various type/lookup handles used by jobs and scheduling.
(Nested types) CheckBirthJob, SumBirthJob, TypeHandle
Internal job structs. CheckBirthJob is a Burst-compiled IJobChunk that contains the main logic for evaluating and spawning births. SumBirthJob aggregates debug counter into m_DebugBirth.

Properties

None (no public properties are exposed by this system).

Constructors

public BirthSystem()
Default constructor. Initialization of managed references and native containers happens in OnCreate; the constructor is preserved for the runtime.

Methods

public override int GetUpdateInterval(SystemUpdatePhase phase)
Returns the update interval used by the system scheduler. The implementation computes an interval based on kUpdatesPerDay and a factor (262144 / (kUpdatesPerDay * 16)) to throttle how frequently the system runs relative to simulation phases.
[Preserve] protected override void OnCreate()
Initializes native counters (m_DebugBirthCounter, m_DebugBirth), acquires references to dependent systems (EndFrameBarrier, SimulationSystem, CityStatisticsSystem, TriggerSystem), builds EntityQueries (citizens, citizen prefabs, citizen parameters), and marks queries required for update to ensure they exist before scheduling jobs.
[Preserve] protected override void OnDestroy()
Disposes native containers (m_DebugBirthCounter, m_DebugBirth).
[Preserve] protected override void OnUpdate()
Main scheduling method. Computes the current update frame index for birth checks, constructs and schedules CheckBirthJob (collecting prefab/archetype lists asynchronously), wires dependencies with CityStatisticsSystem and TriggerSystem, adds the job handle to EndFrameBarrier as a producer, and schedules SumBirthJob to copy the birth count to the debug NativeValue.

CheckBirthJob details: - Filters chunks by UpdateFrame shared component so each citizen is only processed in its assigned update frame. - Skips non-adults, tourists, commuters, and males (depending on citizen flags). - Ensures the household has a property (renter/property owner) as birthplace. - Examines household members to add adult-female bonus to birth rate if an adult male is present. - Applies student adjustment if the prospective mother is a student. - Uses RandomSeed to determine whether to spawn a baby using base birth rate normalized by kUpdatesPerDay. - Spawns a baby by creating an entity with a random citizen prefab/archetype, setting PrefabRef, HouseholdMember, Citizen, and CurrentBuilding components. - Increments m_DebugBirthCounter and enqueues a StatisticsEvent for births.

SumBirthJob details: - Copies the count from m_DebugBirthCounter to m_DebugBirth.value for debug inspection.

[MethodImpl(MethodImplOptions.AggressiveInlining)] private void __AssignQueries(ref SystemState state)
Compiler-generated helper used during OnCreateForCompiler to ensure queries are assigned; no runtime logic beyond setup.
protected override void OnCreateForCompiler()
Compiler helper that calls __AssignQueries and assigns type handles via __TypeHandle.__AssignHandles. Used to support generated code for ECS type handles.

Usage Example

// Example: Adjust the birth chance (field present on the system). Note: the system's
// current code does not read m_BirthChance for calculations; use this pattern
// to access the system and change public fields or to extend behavior in your mod.
[Preserve]
protected override void OnCreate()
{
    base.OnCreate();
    var birthSystem = base.World.GetOrCreateSystemManaged<Game.Simulation.BirthSystem>();
    if (birthSystem != null)
    {
        // This field exists on the system, but the built-in CheckBirthJob uses
        // CitizenParametersData for probabilities. Changing this value alone
        // will not affect births unless you modify the system's job logic.
        birthSystem.m_BirthChance = 50;
    }
}

Notes and modding tips: - To change actual birth probabilities at runtime, modify the CitizenParametersData singleton (read/written via the appropriate queries) or replace/patch the CheckBirthJob logic. The system reads CitizenParametersData.m_BaseBirthRate, m_AdultFemaleBirthRateBonus, and m_StudentBirthRateAdjust. - New entities are created via EndFrameBarrier.CreateCommandBuffer().AsParallelWriter(); if you alter spawn behavior ensure you use an ECB (EntityCommandBuffer) and preserve job dependencies by adding produced job handles to the barrier. - The system relies on citizen prefab lists (m_CitizenPrefabs and m_CitizenPrefabArchetypes) gathered from m_CitizenPrefabQuery; ensure your custom citizen prefabs are available if you intend to spawn custom citizens.