baking-type-cleanup-component

BakingType Cleanup Component — Entity Lifecycle Tracking

Intent

Track entity lifecycle (creation, re-parenting, destruction) within the incremental baking pipeline using ICleanupComponentData that survives entity destruction but is still stripped from the runtime world.

Use When

A baking system must detect which entities were destroyed or re-parented between baking passes, and recompute dependent data (e.g., compound bounding boxes when a child is removed).

Avoid When

Simple single-pass baking without lifecycle tracking — unnecessary complexity. Avoid in the runtime world — ICleanupComponentData without [BakingType] persists into the runtime world and requires explicit removal.

Senior Pattern

• Struct implementing both ICleanupComponentData and tagged with [BakingType].
• Baking system adds cleanup component to newly baked entities: query WithNone WithAll.
• Destroyed entities: cleanup survives, [BakingType] primary component is removed. Query WithNone WithAll catches them.
• Re-parented entities: compare stored Parent in cleanup to current Parent component.
• After processing, RemoveComponent the cleanup from destroyed entities to avoid stale accumulation.

Code Template

[BakingType]
public struct BoundingBoxCleanup : ICleanupComponentData
{
    public Entity PreviousParent;
}

[WorldSystemFilter(WorldSystemFilterFlags.BakingSystem)]
public partial struct BoundingBoxLifecycleSystem : ISystem
{
    public void OnUpdate(ref SystemState state)
    {
        // Add cleanup to new entities
        var newQuery = SystemAPI.QueryBuilder()
            .WithAll<BoundingBox>()
            .WithNone<BoundingBoxCleanup>()
            .Build();
        state.EntityManager.AddComponent<BoundingBoxCleanup>(newQuery);

        // Detect destroyed entities (cleanup survives, BoundingBox gone)
        var destroyedEntities = SystemAPI.QueryBuilder()
            .WithAll<BoundingBoxCleanup>()
            .WithNone<BoundingBox>()
            .Build()
            .ToEntityArray(Allocator.Temp);

        foreach (var entity in destroyedEntities)
        {
            var cleanup = state.EntityManager.GetComponentData<BoundingBoxCleanup>(entity);
            // Trigger recompute on previous parent
            TriggerParentRecompute(ref state, cleanup.PreviousParent);
            state.EntityManager.RemoveComponent<BoundingBoxCleanup>(entity);
        }
        destroyedEntities.Dispose();
    }
}