unity-dots-ecs

Unity DOTS / ECS

Overview

Unity's Entities package stores data in tightly packed chunks and runs Burst-compiled jobs over it in parallel. It scales to tens of thousands of entities where GameObjects choke — and it makes simple gameplay code more verbose. Use it where the scale needs it, follow the project's existing split between GameObjects and entities, and never introduce DOTS into a GameObject project on your own initiative.

Core principle: Components are plain data, systems are Burst-compiled ISystems scheduling jobs, and structural changes go through an entity command buffer.

When it is worth it

The pieces

// Data: unmanaged structs
public struct Speed : IComponentData { public float Value; }
public struct Target : IComponentData { public float3 Position; }

// Authoring + baking: designers edit a MonoBehaviour in a subscene; the baker turns it into components
public sealed class SpeedAuthoring : MonoBehaviour {
    public float value = 5f;
    sealed class Baker : Baker<SpeedAuthoring> {
        public override void Bake(SpeedAuthoring a) {
            var e = GetEntity(TransformUsageFlags.Dynamic);
            AddComponent(e, new Speed { Value = a.value });
        }
    }
}

// Behaviour: a Burst-compiled ISystem scheduling a parallel IJobEntity
[BurstCompile]
public partial struct SeekSystem : ISystem {
    [BurstCompile] public void OnCreate(ref SystemState state) => state.RequireForUpdate<Speed>();

    [BurstCompile] public void OnUpdate(ref SystemState state) {
        new SeekJob { Dt = SystemAPI.Time.DeltaTime }.ScheduleParallel();
    }
}

[BurstCompile]
partial struct SeekJob : IJobEntity {
    public float Dt;
    void Execute(ref LocalTransform transform, in Speed speed, in Target target) {
        var to = target.Position - transform.Position;
        var dist = math.length(to);
        if (dist > 0.01f) transform.Position += to / dist * math.min(speed.Value * Dt, dist);
    }
}