Creating entities at runtime: Any entity I make a child immediately unparents the following frame

Unity Engine
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1

Hi all,

I am foregoing the baking process and am creating and managing my entities at runtime to facilitate a hybrid approach. This is serving me well so far, but like the title says, whenever I give an entity the Parent component it automatically un-parents itself in the following frame. The parent-child relationship shows correctly before then, adding the Child buffer to the parent as expected, and appearing correct in the Hierarchy view.

I thought it might be because I gave both parent and child a collider and rigidbody, but it even happens on plain entities. Does anyone know what might be causing this?

Unity 6000.0.0b11, Entities 1.2

Thanks <3

2

I’m not in Unity 6 but I’m also using Entities 1.2. May I ask for the code that managed your entity (where you add components, the Parent component in particular)?

3

Of course, thank you for taking a look! For completeness’ sake I’ve included the full file just in case, but here’s the relevant method:

void CreateEntity(EntityHost parentHost) {
        Entity = entityManager.CreateEntity();
        entityManager.SetName(Entity, $"[Hosted] {entityName} ({transform.name})");

        entityManager.AddComponentData(Entity, new LocalTransform {
            Position = transform.position,
            Rotation = transform.rotation,
            Scale = 1f,
        });

        IDynamicAuthoring[] dynamicAuthorings = transform.GetComponents<IDynamicAuthoring>();
        foreach(var authoring in dynamicAuthorings) {
            if(((MonoBehaviour)authoring).enabled) {
                authoring.Bake(this);
            }
        }

        if(parentHost != null) {
            Debug.Log($"Adding {parentHost.name} as parent to {transform.name} ");

            AddComponentData(new Parent { Value = parentHost.Entity });

            Debug.Log(entityManager.GetComponentData<Parent>(Entity));
        }
    }

9834627–1414707–EntityHost.cs (4.31 KB)

4

Thanks for the script! Right off the bat:

  • Did you test the while loop in the BuildChildEntityMap? It might cause a bug because it’s not changed inside the loop. This can be converted to a better recursion method instead.
  • I don’t have a safe scene to test this but, I quickly dropped it in a scene and immediately received an error with the entityManager. You don’t need to cache the EntityManager for your use case.
5

The building of the entities is working as expected. If I pause the editor before hitting Play, I can see all the right entities, with all of their correct components and relationships. The problem is that the parent-child relationship is immediately broken the following frame, and I can’t for the life of me figure out why.

You’re right on the caching though; made it a convenience getter instead. (I’ll still need it after Awake() as the hosts are pooled)

6

AddComponentData(Entity, new Parent { Value = parentHost.Entity });

Are you missing the Entity part here?

7

I exposed some methods with identical names in my EntityHost MB to more easily allow my runtime “bakers” to add components. So good catch, but nope!

8

ParentSystem code suggests LocalToWorld is needed for the hierarchical entities. Try adding that.

9

Dang, I was hopeful for a second. But no dice, it still un-parents after 1 frame

10

Did you add LocalToWorld on the parent?

3 Likes
11

…I did not. Great catch, thank you so much! I can sleep easy tonight haha

1 Like