baking-system

Baking System

Intent

Perform post-Baker ECS processing in the baking world — cross-entity aggregation, complex structural changes, blob asset construction, and render mesh setup — that cannot be expressed within a single Baker.

Use When

The baking work requires querying multiple entities produced by different Bakers, performing structural changes that would invalidate Baker iteration, or accessing ECS APIs not available to Bakers (e.g., full EntityManager, ComponentLookup across entities).

Avoid When

The work can be done entirely within one Baker — prefer Baker-local logic to avoid the split-responsibility complexity of Baker + baking system.

Senior Pattern

• [WorldSystemFilter(WorldSystemFilterFlags.BakingSystem)] on a partial struct : ISystem.
• Baking systems run after all Bakers complete, with full ECS API access.
• Use SetChangedVersionFilter and RequireForUpdate to skip unnecessary work on incremental rebakes.
• For structural changes while iterating: call query.ToEntityArray(Allocator.Temp) first, then process via EntityManager random access — never mutate archetypes inside a SystemAPI.Query foreach.
• Baking systems cannot register DependsOn — Baker must stage all dependency data as [BakingType] components.

Code Template

[WorldSystemFilter(WorldSystemFilterFlags.BakingSystem)]
[UpdateAfter(typeof(TransformBakingSystem))]
public partial struct BoundingBoxAggregateSystem : ISystem
{
    private EntityQuery m_ChangedQuery;

    public void OnCreate(ref SystemState state)
    {
        m_ChangedQuery = SystemAPI.QueryBuilder()
            .WithAll<BoundingBox, BoundingBoxCleanup>()
            .Build();
        m_ChangedQuery.SetChangedVersionFilter(ComponentType.ReadOnly<BoundingBox>());
        state.RequireForUpdate(m_ChangedQuery);
    }

    public void OnUpdate(ref SystemState state)
    {
        // ToEntityArray first — then structural changes are safe
        var entities = m_ChangedQuery.ToEntityArray(Allocator.Temp);
        foreach (var entity in entities)
        {
            var box = state.EntityManager.GetComponentData<BoundingBox>(entity);
            // aggregate, then write runtime component
            state.EntityManager.SetComponentData(box.Parent, ComputeAggregateBounds(entity));
        }
        entities.Dispose();
    }
}