Intended way of instantiate a entities in parent child relationship with entitycommandbuffer?

let's say I have entities A-B-C in a parent child hierarchy. What is the best way of repeatedly instantiate that group of entities with hierarchy maintained?

 

Also wondering this. I'm doing

commandBuffer.Instantiate(index, entity);

on a Parent entity with the expectation that it would instantiate copies of it's child entities as well. Instead it only instantiates the parent entity - I guess it ignores Dynamic Buffers?

 

This should be achievable with a LinkedEntityGroup:
https://gametorrahod.com/gameobject-conversion-ecosystem-code-tour/

 

It seems some things reference in that article are out of date - "AddReferencedPrefabAsGroup" is not a thing. But it did set me on the right track.

When you convert a gameobject using "GameObjectConversionUtility.ConvertGameObjectHierarchy" it will convert the hierarchy as expected AND put everything into a LinkedEntityGroup. At that point you can call instantiate on the converted entity and it will work as expected.

However if you use the "IConvertGameObjectToEntity" workflow, it will NOT put everything into a LinkedEntityGroup. It creates the child buffer and parent components as expected but unlike the ConversionUtility method it doesn't add a LinkedEntityGroup to the parent, meaning if you try to instantiate an entity created via IConvertGameObjectToEntity you will only instantiate the parent.

I'm not sure if this is a bug or if there's a good reason for the different behaviour between the two methods.

 

Messing with this more in the newest version (p.32) and we now have:

GameObjectConversionSystem.AddLinkedEntityGroup( GameObect )

If you call this on your parent object which has the ConvertToEntity script it appears to add all children in that parent in a LinkedEntityGroup on the parent. So along with whatever other ComponentConversion you do on your parent you can add:

Code (CSharp):

1.  
2. public class LinkedGroupConversion : MonoBehaviour, IConvertGameObjectToEntity
3. {
4.     public void Convert(Entity entity, EntityManager dstManager, GameObjectConversionSystem conversionSystem)
5.     {
6.         conversionSystem.AddLinkedEntityGroup(gameObject);
7.     }
8. }
9.  

Then when you instantiate that parent entity from the ECS side it will work the same way as it does on the Gameobject side.

 

Omg this code is amazing for me thanks

 

This saved my butt. Thanks

I'm pretty sure this has been changed to

DeclareLinkedEntityGroup