Convert And Inject Game Object in Prefabs

Is there a standard way of instantiating an Entity that has a child with ConvertToEntity-(Convert And Inject Game Object) somewhere in it's hierarchy?

Example:
I have a PlayerShip prefab and one of it's children is an Engine GameObject with with Visual Effect component so that I may use VFX Graph to draw engine exhaust.
Currently I set ConvertToEntity-(Convert And Destroy) component on a PlayerShip and ConvertToEntity-(ConvertInject Game Object) and CopyTransformToGameObject components on Engine.

Situation 1 - Instantiating by putting a prefab in a scene
This works just fine. Whole hierarchy is converted to entities destroyed but Engine which is just converted and has it's transform copied every turn form accompanying entity.


Situation 2 - Instantiating by calling EntityCommandBuffer.Instantiate()
Sometimes I don't need my PlayerShip prefab spawned right away but rather as a result of some event. So I made PlayerSpawner IComponentData and accompanying PlayerSpawnerAuthoring MB with IDeclareReferencedPrefabs. Unfortunately when I spawn my PlayerShip prefab with EntityCommandBuffer.Instantiate() entities are spawned correctly but Engine GameObject that my VFX Graph is attached to doesn't.

Is there a way to instantiate GameObjects in Situation 2?
Is there an easy way to use VFX graph with Unity ECS atm or do we have to wait longer for it?

 

The standard way is by calling AddHybridComponent while in conversion, and that will create a "companion game object" hosting those selected components to go together with your convertible parts. You can use the convert and destroy mode at the top of ship with nothing special or any Stops on any of the child.

As a part of conversion, get a conversion mapper system (in your GameObjectConversionSystem or in your IConvertGameObjectToEntity) and call .AddHybridComponent to add your VFX component from down the tree. The result is that the primary entity that would be generated from game object of that component would have an additional CompanionLink component that link to a hidden new game object with VFX component migrated to it. That is the companion game object created as a part of conversion. The hidden companion game object then has a system similar to copy transform to game object to sync its classic Transform position to that primary entity.

If used on a prefab, then the result will contains Prefab + LinkedEntityGroup + CompanionLink. The CompanionLink make it EntityManager.Instantiate compatible, it will also duplicate the hidden companion game object making it seamless that also the not convertible part could get instantiated together with pure ECS part.

 

@5argon You, sir, are a hero Works like a charm and in general AddHybridComponent solves most of the problems I ever had with interop between ECS and MonoBehaviors

 

Just to add that I may have found a bug about AddHybridComponent when having multiple things to save to companion object. (not sure but already submitted : https://fogbugz.unity3d.com/default.asp?1217971_hehg8e7i5msfhrjc) For example this cube where I would like to keep 2 nested TextMeshPro after conversion. I have written like following in order to save everything required of both :

Code (CSharp):

1. using TMPro;
2. using Unity.Entities;
3. using Unity.Transforms;
4. using UnityEngine;
5.  
6. internal class GridBarAuthoring : MonoBehaviour, IConvertGameObjectToEntity
7. {
8. #pragma warning disable 0649
9.     [SerializeField] private TextMeshPro leftText;
10.     [SerializeField] private TextMeshPro rightText;
11. #pragma warning restore 0649
12.  
13.     public void Convert(Entity entity, EntityManager dstManager, GameObjectConversionSystem conversionSystem)
14.     {
15.         if (leftText != null)
16.         {
17.             var go1 = leftText.gameObject;
18.             conversionSystem.AddHybridComponent(leftText);
19.             conversionSystem.AddHybridComponent(go1.GetComponent<RectTransform>());
20.             conversionSystem.AddHybridComponent(go1.GetComponent<MeshRenderer>());
21.             conversionSystem.AddHybridComponent(go1.GetComponent<MeshFilter>());
22.             conversionSystem.AddHybridComponent(go1.GetComponent<CanvasRenderer>());
23.         }
24.  
25.         if (rightText != null)
26.         {
27.             var go2 = rightText.gameObject;
28.             conversionSystem.AddHybridComponent(rightText);
29.             conversionSystem.AddHybridComponent(go2.GetComponent<RectTransform>());
30.             conversionSystem.AddHybridComponent(go2.GetComponent<MeshRenderer>());
31.             conversionSystem.AddHybridComponent(go2.GetComponent<MeshFilter>());
32.             conversionSystem.AddHybridComponent(go2.GetComponent<CanvasRenderer>());
33.         }
34.     }
35. }

But turns out when both were to be converted, I always got an error about right one failing to convert. On attach code debugging it seems the left one got all 5 components saved but only RectTransform for the right one, so it attempts to destroy e.g. CanvasRenderer and then it error because other component has required on it.

If I convert only one of them then it works fine. Maybe this bug only occurs if you have 2 similar things on the same conversion to migrate.

 

Is AddHybridComponent the new workflow to convert all none-convertible Monobehaviours?
Mostly:
- Animator
- Camera
- UI (Canvas, Text etc)
- Particle Systems

When did Unity release this feature?

 

This is the first time I've heard of HybridComponent, no matter how much time you spend with ECS you always find some new hidden detail, geeze. Been a while since I looked at the samples, it seems the "HybridComponent" concept was added three months ago. There's a small explanation:
https://github.com/Unity-Technologi...sts/HybridComponent#hellocube-hybridcomponent

 

Hybrid Components are an experimental feature, their use isn't recommended yet.

So tempting....

 

Wow, that was easy . Eyeballing the components it creates internally, it looks it's doing almost exactly the same thing that I was planning to do.

The only downside is that probably nothing is pooled...

That being sad without any further optimization I'm having 441 archers firing once per second on 441 targets (resulting in ≈3*441=1320 Trail Renderers visible at any time)...

90 effing FPS on a Pixel 4XL and rock solid 45 FPS on a 3 year old Pixel XL (for a release build, not even master)



Things scale so well with ECS, it's just nasty

Edit:
Sorry, this makes me so happy

2000 units, 3000 Trail Renderers, Pixel 4XL, 60FPS

 

Sighs, it turns out ParticleSystems don't work when I do exactly the same thing that worked with the Trail Renderers, lol... anyone has an idea why that would be?

 

Merp, turns out you need to add both the

ParticleSystem

and the

ParticleSystemRenderer

in your

IConvertGameObjectToEntity

.

Code (CSharp):

1. public class TestPrefabAssetRegistryEntryAuthoring : MonoBehaviour, IConvertGameObjectToEntity {
2.    public void Convert(Entity entity, EntityManager entityManager, GameObjectConversionSystem gameObjectConversionSystem) {
3.       if (TryGetComponent<ParticleSystem>(out var particleSystem)) {
4.          gameObjectConversionSystem.AddHybridComponent(particleSystem);
5.       }
6.       if (TryGetComponent<ParticleSystemRenderer>(out var particleSystemRenderer)) {
7.          gameObjectConversionSystem.AddHybridComponent(particleSystemRenderer);
8.       }
9.    }
10. }

Haven't done performance tests, but eyeballing it, it pooling doesn't seem super necessary either

 

I wonder there is pooling under the hood?

 

Yes. It will sync the transform every frame (it has to).

 

So it will pool the monobehavior instances so that when you instantiate a hybrid component it won't create a new monobehaviour particle system if it can find a previous one that has been deactivated?

 

I would assume there is no pooling, but (so far) I haven't found it necessary.

Exhibit A: Every one of those fireballs is a particle system instantiated using the above AddHybridComponent. (It's running on high end mobile phone at >40FPS without hiccups on instantiation). (Iirc that wasn't even batched, but only 90% sure.)

 

Do you happen to know if there's a way to get the Prefab component onto a GameObject in-editor? I'm having to manually add it for now in a conversion behaviour.

 

hey, how are you handling garbage collection? it seems that creating a simple particles system with the hybridcomponent causes garbage collection in the CompanionGameObjectUpdateTransformSystem. evident in builds with safety off.

 

I've been using a pool that I adapted from AndersMalmgren - https://forum.unity.com/threads/perfomant-audiosource-pool.503056/ for my hybrid particle systems and audio clips. It's quite handy because in addition to avoiding garbage creation, it automatically recycles each particle system or audio clip when it finishes playing (by checking isEmitting and isPlaying).

 

Anyone figure out how to do simple entity-tethered particle systems now that AddHybridComponent() has been removed in 0.50?

 

Try to add them by dstManager.AddComponentObject().
Note that it currently does support only few built-in types, like ParticleSystem, MeshRenderer, etc..

 

Thanks, I actually already tried using dstManager.AddComponentObject().

I found out that the problem is because i am loading prefabs with addressables in the introductory title-scene and then when i try to instantiate them in the actual game-scene, the game-objects (particle systems) for some reason get deleted in 0.50.

So basically... it's a problem with keeping companion objects between scene changes.

[Edit - I found an ugly hacky workaround. It sucks, but it's better than nothing]

 

Any chance you could share your findings?

 

I have a little more info in my posts here: https://forum.unity.com/threads/experimental-entities-0-50-is-available.1253394/page-2#post-7988388

So basically, to keep the companion objects between my title-scene and the main game, I had to use LoadSceneMode.Additive and remove all game-objects in my title scene manually. It's stupid. It only really works because it's my title scene and there's not very much in it, but if I was trying to keep the prefabs between two complicated scenes it would be a nightmare.

Entities 0.17 never had this issue. I wish there was a better workaround, but so far I have not seen any legit solutions.