Custom PostBakingSystem cannot find Child Entities

[frosty basalt]

I’m trying to get the PhysicsJoints that Unity creates if I add a ConfigurableJoint to an Entity, so Unity will create 2 entities as a child with PhysicsJoints, I then created a PostBaking System, and in it I put a Debug to check how many childs entities there were inside these Components, and it shows 0, even though I can clearly see them in the Entities Hierarchy, here is the code below and the images

using System.Diagnostics;
using Unity.Burst;
using Unity.Entities;
using Unity.Physics;
using Unity.Transforms;
using static SyncPhysicsJointAuthoring;

[WorldSystemFilter(WorldSystemFilterFlags.BakingSystem)]
[UpdateInGroup(typeof(PostBakingSystemGroup))]
partial struct SyncPhysicsJointBakingSystem : ISystem
{

    //[BurstCompile]

    public void OnUpdate(ref SystemState state)
    {
        foreach (RefRW<SyncPhysicsJointComponent> syncJoint in SystemAPI.Query<RefRW<SyncPhysicsJointComponent>>())
        {
            Entity mainEntity = syncJoint.ValueRO.thisEntity;

            UnityEngine.Debug.Log($"Entity {mainEntity} has Child: {state.EntityManager.HasComponent<Child>(mainEntity)}");

            if (state.EntityManager.HasComponent<Child>(mainEntity))
            {

                DynamicBuffer<Child> childBuffer = state.EntityManager.GetBuffer<Child>(mainEntity);

                int jointCount = 0;
                UnityEngine.Debug.Log($"Checking entity: {mainEntity}");

            }
        }
    }
}

And I did add [WorldSystemFilter(WorldSystemFilterFlags.BakingSystem)] [UpdateInGroup(typeof(PostBakingSystemGroup))]

[mighty forum]

Child buffer is only created at runtime

it's a cleanup component

    public struct Child : ICleanupBufferElementData
    {
        /// <summary>
        /// A child entity
        /// </summary>
        public Entity Value;
    }```

which means it can't be baked or used during baking

it's added at runtime in the ParentSystem

[frosty basalt]

Thank you for the reply again Tertle!

When you say runtime, it's when I press Play? Or Post baking?

As you can see in the image, the PhysicsJoint childs are inside the Entity with the ConfigurableJoint and I didn't press play.

[mighty forum]

I'm just commenting on your above code which is reading the child buffer in a baking system

[frosty basalt]

How would you check if there was a child in an Entity on PostBaking?

[mighty forum]

LinkedEntityGroup should have them all

[frosty basalt]

Will take a look later, thank you Tertle!

[mighty forum]

It can have other things in there though, so if you want to know it's actually a child in the hierarchy vs just a linked entity you'll need to check for the Parent component and make sure it points to the root entity

(The parent component is how the Child buffer is built)

[frosty basalt]

For now I'm getting the component during runtime

[frosty basalt]

I don't understand, however I will study this carefully later

[mighty forum]

LEG will always have the root entity in it

LEG can also have other entities linked to it that aren't in hierarchy

via things like
baker.CreateAdditionalEntity()

these entity will be created/destroyed linked to the root entities lifecycle

but it isn't in the transform hierarchy

they might not even have transforms