Can't use EntityCommandBuffer inside Entity.ForEach

Hi

When trying to create an entity or instantiate inside ForEach. It will give me the error.

Code (CSharp):

1. Assets\Scripts\Systems\Render.cs(140,13): error DC0004: Entities.ForEach Lambda expression captures a non-value type 'this'. This is only allowed with .WithoutBurst() and .Run()
2.  

Pseudocode below.

Code (CSharp):

1. public partial class Render : SystemBase
2.     {
3.         EndSimulationEntityCommandBufferSystem m_EndSimulationEcbSystem;
4.        
5.         protected override void OnCreate()
6.         {      
7.             m_EndSimulationEcbSystem = World
8.                 .GetOrCreateSystem<EndSimulationEntityCommandBufferSystem>();
9.         }
10.  
11.         protected override void OnUpdate()
12.         {
13.             CameraTransform tempCameraTransform = default;
14.             EntityCommandBuffer ecb = m_EndSimulationEcbSystem.CreateCommandBuffer();
15.            
16.             Entities
17.                 .ForEach((Entity entity,
18.                     ref Translation translation,
19.                     ref Scale scale,
20.                     in LinkWithBackend linkWithBackend,
21.                     in Parent parent) =>
22.                 {
23.                     ecb.CreateEntity(); // no allowed anymore
24.                 }).Run();
25.            
26.         }
27.     }

Thank you

 

You doing thing in job in parallel. You need pass job index into ecb parallel writer.

Type ecb. in visual studio (with dot) and see intellisense suggestion for parallel writer. Your job for each also need index. Look forum and repos for parallel writing into ecb.

 

I thought that when I use .Run() it will run in the main thread so it should work without parraler.

And when I try to run it Schedule or ScheduleParraler I still run into this issue. Both these codes were working before.

Code (CSharp):

1. EntityCommandBuffer.ParallelWriter ecb = m_EndSimulationEcbSystem.CreateCommandBuffer().AsParallelWriter();
2.  
3. Entities
4.         .WithAll<ZoomLevelOne>()
5.         .ForEach((int entityInQueryIndex,
6.             Entity entity,
7.             ref Translation translation,
8.             ref Scale scale,
9.             in LinkWithBackend linkWithBackend) =>
10.         {
11.             var frontEndEntity = ecb.Instantiate(entityInQueryIndex, _ring);
12.  
13.         }).ScheduleParallel();
14.  
15.         or
16.  
17.         .Schedule()

 

Sorry, yes you are right. I missed you used Run.

I'm that case, your problem are refs and ins. You can not have them "floating". You need read o write values from/to them inside a foreah job. Or remove them from for each query, if not needed.
Or use. WithAll,. WithAny,. WithNone. And use corresponding components, if you require them in a query.

 

Sry this was minified code. I will add the full code here. Those components are used inside ForEach.

And Methods that are called inside ForEach are static. If I remove ecb code it will work fine or if I add WithoutBurst().

Code (CSharp):

1. CameraTransform tempCameraTransform = default;
2.             EntityCommandBuffer.ParallelWriter ecb = m_EndSimulationEcbSystem.CreateCommandBuffer().AsParallelWriter();
3.          
4.             Entities
5.                 .ForEach((Entity entity, in CameraTransform cameraTransform) =>
6.                 {
7.                     tempCameraTransform = cameraTransform;
8.                 }).Run();
9.          
10.             var backendEntities = _backendEntities;
11.             Entities
12.                 .WithAll<ZoomLevelOne>()
13.                 .ForEach((int entityInQueryIndex,
14.                     Entity entity,
15.                     ref Translation translation,
16.                     ref Scale scale,
17.                     in LinkWithBackend linkWithBackend) =>
18.                 {
19.                     if(backendEntities.ContainsKey(linkWithBackend.BackendEntity))
20.                     {
21.                         var gameTranslation = backendEntities[linkWithBackend.BackendEntity].GameTranslation;
22.                         var gameScale = backendEntities[linkWithBackend.BackendEntity].GameScale;
23.                         var innerTranslation = InnerTranslation(gameTranslation, tempCameraTransform);
24.                      
25.                         var computedScale = ComputeScale(gameScale, tempCameraTransform);
26.  
27.                         if (computedScale < 1f)
28.                         {
29.                             // Destroy Entity
30.                             ecb.DestroyEntity(entityInQueryIndex, entity);
31.  
32.                             var frontEndEntity = ecb.Instantiate(entityInQueryIndex, _ring);
33.                             ecb.AddComponent<ZoomLevelTwo>(entityInQueryIndex, frontEndEntity);
34.                             ecb.SetComponent(entityInQueryIndex, frontEndEntity, new Translation()
35.                             {
36.                                 Value = InnerTranslation(backendEntities[linkWithBackend.BackendEntity].GameTranslation, tempCameraTransform)
37.                             });
38.                             ecb.AddComponent(entityInQueryIndex, frontEndEntity, typeof(LocalToWorld));
39.                          
40.                             ecb.AddComponent(entityInQueryIndex, frontEndEntity, new Scale
41.                             {
42.                                 Value = 1
43.                             });
44.                          
45.                             ecb.AddComponent(entityInQueryIndex, frontEndEntity, linkWithBackend);
46.                         }
47.                      
48.                         if(computedScale > 1)
49.                         {
50.                             scale.Value = gameScale.Scale / tempCameraTransform.OneUnitInMeters;
51.                         }
52.                      
53.                         translation.Value = innerTranslation;
54.                     }
55.                 }).ScheduleParallel();

 

Maybe its a bug? Only weird thing I noticed is on line 38

Not sure burst can handle that since its a class. Try this instead:

Code (CSharp):

1. ecb.AddComponent<LocalToWorld>(entityInQueryIndex, frontEndEntity)

 

No dice with that change. Thanks for the suggestion.

 

Try assign ecb.CreateEntity() to variable from your first example.
Like for example
Entity entity = ecb.CreateEntity();
I Don think that will help, but worth a shot.

 

Thanks, for helping guys. I did figure it out.
There were two issues. Somehow I messed up the unity package and had to restore it and another issue was (_ring) variable that was not assigned to the local scope.

The error message is quite bad for finding those issues.

 

Hello,
Sorry to piggyback of this thread, but I'm having the same issue. And as noted the error message leaves you out to dry.

I always run into this error:
Assets\Scripts\Atmosphere\AtmosphereSystem.cs(23,9): error DC0004: Entities.ForEach Lambda expression captures a non-value type 'this'. This is only allowed with .WithoutBurst() and .Run()

And I have no idea what is causing it and what to do about it. Would you be so kind as to help? Thank you!

Code (CSharp):

1. [BurstCompile]
2. public partial class AtmosphereSystem : SystemBase
3. {
4.     EntityQuery atmoQuery;
5.     [ReadOnly] NativeArray<Entity> allVoxelEntities;
6.     [ReadOnly] ComponentDataFromEntity<AtmosphereVoxel> allAtmoVoxel;
7.     [ReadOnly] BufferFromEntity<IntElement> allElementBuffer;
8.  
9.     protected override void OnUpdate() {
10.         NativeList<AtmoNeeds> needs = new NativeList<AtmoNeeds>(Allocator.TempJob);
11.  
12.         allVoxelEntities = atmoQuery.ToEntityArray(Allocator.TempJob);
13.         allAtmoVoxel = GetComponentDataFromEntity<AtmosphereVoxel>();
14.         allElementBuffer = GetBufferFromEntity<IntElement>();
15.  
16.         Entities.ForEach((AtmosphereVoxel atmo, DynamicBuffer<IntElement> dynamicBuffer) => {
17.             for (int i = 0; i < dynamicBuffer.Length; i++ ) {
18.         //find matching voxel
19.                 for(int x = 0; x < allVoxelEntities.Length; x++) {
20.                     Entity curEntity = allVoxelEntities[x];
21.                     AtmosphereVoxel n_atmo = allAtmoVoxel[curEntity];
22.                     DynamicBuffer<IntElement> n_dynamicBuffer = allElementBuffer[curEntity];
23.                     //do stuff here...
24.                 }
25.                
26.                 Debug.Log($"need {needs.Length}");
27.             }
28.         }).Schedule();
29.  
30.         needs.Dispose();
31.     }

 

Lambdas can only capture local variables to work with Burst, not member variables.

 

As DreamingLation mentioned, define
allVoxelEntities, allAtmoVoxel, allElementBuffer inside OnUpdate.

Also,
Entities.ForEach((AtmosphereVoxel atmo, DynamicBuffer<IntElement> dynamicBuffer)
Dynamic Buffer should be first.
And use IN and REF keywords, for read, read / write.

 

Thank you for the prompt reply!

How do I know the order in which Entities.Foreach arguments should appear in?

I am getting a two new error concerning the disposal of native arrays:
A Native Collection has not been disposed, resulting in a memory leak. Allocated from:
AtmosphereSystem:OnUpdate() (at Assets\Scripts\Atmosphere\AtmosphereSystem.cs:25)

Code (CSharp):

1. protected override void OnUpdate() {
2.         NativeList<AtmoNeeds> needs = new NativeList<AtmoNeeds>(Allocator.Temp);
3.  
4.         NativeArray<Entity> allVoxelEntities = atmoQuery.ToEntityArray(Allocator.TempJob);
5.         ComponentDataFromEntity<AtmosphereVoxel> allAtmoVoxel = GetComponentDataFromEntity<AtmosphereVoxel>();
6.         BufferFromEntity<IntElement> allElementBuffer =  GetBufferFromEntity<IntElement>();
7.  
8.         //setup neighbor index
9.         NativeArray<Entity> neighbors = new NativeList<Entity>(6, Allocator.Temp);      
10.  
11.         Entities.ForEach((in DynamicBuffer<IntElement> dynamicBuffer, in AtmosphereVoxel atmo) => {
12.             //do stuff
13.         }).Schedule();
14.  
15.         allVoxelEntities.Dispose();
16.         neighbors.Dispose();
17.         needs.Dispose();
18.     }

I call .dispose() at the end of the OnUpdate, where should I be putting them instead? I tried inside the foreach before .schedule but no difference.
Is using Allocator.TempJob correct? It complained if I used Allocator.Temp in a diffrent error.

The second error is:
InvalidOperationException: The writeable ComponentDataFromEntity<AtmosphereVoxel> AtmosphereSystem_LambdaJob_0_Job.JobData.allAtmoVoxel is the same ComponentTypeHandle<AtmosphereVoxel> as AtmosphereSystem_LambdaJob_0_Job.JobData.__atmoTypeHandle, two containers may not be the same (aliasing).
AtmosphereSystem.OnUpdate () (at Assets/Scripts/Atmosphere/AtmosphereSystem.cs:28)

I think the error says I maybe accessing the same set of data? But not sure what it actually means and what to do about it.

Thank you for your help!

 

Lime 5 and 11 conflicts wih each other. You can not have two same components in for each, in such form.

You can also avoid using, by using Get component inside for each. It is special method for for each lambda.

Also, if you use outside get components, mark them read only, or read write, with false, or true bool.

Native colectioms created outside entities for each, need to be disposed. Unless are persistent. Then you dispose them at game end/close.

You better look into unity samples on git. You ot tons of issues here with a code. Follow samples and create your systems.