How to Create Entity from Prefab in Job?

On the main thread, I currently create prefabs by using a helper method like the following.

Spoiler: GetGhostPrefab helper

Code (CSharp):

1.     protected Entity GetGhostPrefab<T>() where T : struct, ISnapshotData<T>
2.     {
3.         var ghostCollection = GetSingleton<GhostPrefabCollectionComponent>();
4.         var ghostId = NetCubeGhostSerializerCollection.FindGhostType<T>();
5.         return EntityManager.GetBuffer<GhostPrefabBuffer>(ghostCollection.serverPrefabs)[ghostId].Value;
6.     }
7.  
8.     protected void SpawnBox() {
9.         Entity box = EntityManager.Instantiate(GetGhostPrefab<BoxSnapshotData>());
10.     }

Is it possible to similarly create entities from prefabs, from within a job? Here is my progress on this particular problem:

- I know I'll need to create an entity using `EntityCommandBuffer` first.
- However, `EntityCommandBuffer` requires an archetype as input.
- Thus... is it possible to extract an archetype from a prefab? Or from a ghost? (Or, is this direction not even advisable?)

Interested in answers but mostly looking for "what is best practice". Worst comes to worst, I could just `EntityManager.CreateArchetype` but it seems nice and clean to have prefabs.

 

I think we're still figuring out best practice.

So here's my … practice Also using NetCode.

I have a number of helpers as well, in

NetworkPrefabs

:

Spoiler: getProjectileEntity helper

Code (CSharp):

1.     public static Entity getProjectileEntity(ComponentSystemBase system)
2.     {
3.         var ghostCollection = system.GetSingleton<GhostPrefabCollectionComponent>();
4.         var ghostId         = NetworkGhostSerializerCollection.FindGhostType<ProjectileSnapshotData>();
5.         return system.EntityManager.GetBuffer<GhostPrefabBuffer>(ghostCollection.serverPrefabs)[ghostId].Value;
6.     }

With this, I get the prefab outside of a job and instantiate it inside a job:

Spoiler: Job example

Code (CSharp):

1. var commandBuffer    = endFrameBarrier.CreateCommandBuffer().ToConcurrent();
2. var prefabProjectile = NetworkPrefabs.getProjectileEntity(this);
3.  
4. Entities.
5.     WithNone<Reload>(). // Reloading weapons do not fire.
6.     WithReadOnly(weaponsMap).
7.     WithAll<Firing>().
8.     ForEach(
9.             // Inside the job, I then instantiate entities from the prefab entity ...
10.             // ... gathering the necessary data for the projectile (not shown).
11.             // then instantiating it:
12.             NetworkPrefabs.instantiateProjectileEntity(
13.                                                        prefabProjectile,
14.                                                        commandBuffer,
15.                                                        entityInQueryIndex,
16.                                                        ref projectile,
17.                                                        ref translation,
18.                                                        ref rotation,
19.                                                        ref velocity,
20.                                                        data.soundsId
21.                                                       );
22.     }).
23.     WithName("FiringJobSystem").
24.     Schedule();
25.  

The instantiation helper is a simple wrapper around

SetComponent

etc in

NetworkPrefabs

:

Spoiler: instantiateProjectileEntity helper

Code (CSharp):

1.     public static Entity instantiateProjectileEntity(
2.         Entity         prefabProjectile, EntityCommandBuffer.Concurrent commandBuffer, int entityInQueryIndex,
3.         ref Projectile projectile,       ref Translation translation, ref Rotation rotation, ref Velocity velocity,
4.         Sounds.Id      sound)
5.     {
6.         var projectileEntity = commandBuffer.Instantiate(entityInQueryIndex, prefabProjectile);
7.         commandBuffer.SetComponent(
8.                                    entityInQueryIndex,
9.                                    projectileEntity,
10.                                    projectile
11.                                   );
12.         commandBuffer.SetComponent(
13.                                    entityInQueryIndex,
14.                                    projectileEntity,
15.                                    translation
16.                                   );
17.         commandBuffer.SetComponent(
18.                                    entityInQueryIndex,
19.                                    projectileEntity,
20.                                    rotation
21.                                   );
22.         commandBuffer.SetComponent(
23.                                    entityInQueryIndex,
24.                                    projectileEntity,
25.                                    velocity
26.                                   );
27.         commandBuffer.SetComponent(entityInQueryIndex, projectileEntity, new NetworkedOneShot { Value = sound });
28.  
29.         return projectileEntity;
30.     }

Curious what other people do.

 

@florianhanke Sick, thanks! Seeing your paradigm is really helpful. I can usually hack something together but I highly doubt my hacks are even close to "best practice".... so this is a step forward.

For posterity: Ignore my archetype "progress" in the original post. For whatever reason, didn't occur to me the command buffer would ofc have an analog for EntityManager.Instantiate. Oops. Florian's code clears that up.

 

Hey cool, glad to hear it helps!