How to instantiate entity and immediate change component in ScheduleParallel?

When i instantiate Entity from prefab - my Entity appears on the point 0,0,0 (that point setted by default Transform component). I want to instantiate my entity in random position, so i create EntityCommandBuffer and do that code inside SystemBase.ForEach(...).ScheduleParallel():

Code (CSharp):

1. Entity spawnedEntity = ecb.Instantiate(entityInQueryIndex, zombiePrefab.prefabEnity);
2.                     ecb.AddComponent<Translation>(entityInQueryIndex, spawnedEntity, new Translation
3.                     {
4.                         Value = new float3(-10f, random.NextFloat(-5f, 5f), 0)
5.                     });

My entity spawns in point 0,0,0 for 1 frame and on the next frame appears on my random position.
How to spawn entity in my random position without appears on position 0,0,0 and not loosing benefits of ScheduleParallel?

 

Use EntityCommandBufferSystem that runs before TransformSystemGroup or apply LocalToWorld manually

 

how to apply LocalToWorld manually?
Here is my full code:

Code (CSharp):

1. public class ZombieSpawnerSystem : SystemBase
2. {
3.     private EndSimulationEntityCommandBufferSystem m_EndSimulationEcbSystem;
4.     private uint seed = 1;
5.     protected override void OnCreate()
6.     {
7.         base.OnCreate();
8.         m_EndSimulationEcbSystem = World.GetOrCreateSystem<EndSimulationEntityCommandBufferSystem>();
9.     }
10.     protected override void OnUpdate()
11.     {
12.         float dt = Time.DeltaTime;
13.         var ecb = m_EndSimulationEcbSystem.CreateCommandBuffer().ToConcurrent();
14.         Random random = new Random(seed++);
15.         Entities
16.             .ForEach((Entity entity, int entityInQueryIndex, ref SpawnDelayComponent spawnDelay, in ZombiePrefabComponent zombiePrefab) =>
17.             {
18.                 spawnDelay.currentTime += dt;
19.                 if (spawnDelay.currentTime > spawnDelay.delayTime)
20.                 {
21.                     spawnDelay.currentTime = 0f;
22.  
23.                     Entity spawnedEntity = ecb.Instantiate(entityInQueryIndex, zombiePrefab.prefabEnity);
24.                     ecb.AddComponent<Translation>(entityInQueryIndex, spawnedEntity, new Translation
25.                     {
26.                         Value = new float3(-10f, random.NextFloat(-5f, 5f), 0)
27.                     });
28.                 }
29.  
30.             })
31.             .ScheduleParallel();
32.         m_EndSimulationEcbSystem.AddJobHandleForProducer(this.Dependency);
33.     }
34. }

 

You can change your code like this for example, rotation part is optional obviously.

Code (CSharp):

1.  
2. if (spawnDelay.currentTime > spawnDelay.delayTime)
3. {
4.     spawnDelay.currentTime = 0f;
5.     Entity spawnedEntity = ecb.Instantiate(entityInQueryIndex, zombiePrefab.prefabEnity);
6.    
7.     var newPosition = new float3(-10f, random.NextFloat(-5f, 5f), 0);
8.     ecb.AddComponent<Translation>(entityInQueryIndex, spawnedEntity, new Translation
9.     {
10.         Value = newPosition
11.     });
12.    
13.     var newRotation = quaternion.identity;
14.     ecb.AddComponent<Rotation>(entityInQueryIndex, spawnedEntity, new Rotation
15.     {
16.         Value = newRotation
17.     });
18.    
19.     ecb.AddComponent(entityInQueryIndex,spawnedEntity, new LocalToWorld
20.     {
21.         Value = new float4x4(newRotation,newPosition)
22.     });
23. }
24.  

 

That works great! Thank you!

I have one more small question: why Unity.Mathematics.Random not so random?
I initialize random that way:

Code (CSharp):

1. Unity.Mathematics.Random random = new Unity.Mathematics.Random(seed++);

Where seed is int and it iterates every frame. When i call random.NextFloat(-5f, 5f) i get numbers like -4.9, -4.8, -4.7, -4.6, ... etc (not exactly that numbers, but close to them)

 

i guess you don't have to create it every frame, just create it once and initialize it with some big number

Code (CSharp):

1. Unity.Mathematics.Random random = new Unity.Mathematics.Random();
2. random.Init(seed++)

 

I was trying to declare random as private variable of my SystemBase class, then initialize it OnCreate with big number, but when i trying get access to it inside Entities.ForEach() - get this error:
Entities.ForEach Lambda expression uses field 'random'. Either assign the field to a local outside of the lambda expression and use that instead, or use .WithoutBurst() and .Run()

 

Just as the error says, assign it to some local variable before ForEach, like var localRand = rand; and use localRand inside ForEach

 

Sorry, still doesn't work.. I declare variable in SystemBase class, then initialize it OnCreate method, then create local variable "rand" in OnUpdate and giving it variable "random". It always give me same float 3.35354

Code (CSharp):

1. public class ZombieSpawnerSystem : SystemBase
2. {
3.     private EndSimulationEntityCommandBufferSystem m_EndSimulationEcbSystem;
4.     Unity.Mathematics.Random random;
5.     protected override void OnCreate()
6.     {
7.         base.OnCreate();
8.         m_EndSimulationEcbSystem = World.GetOrCreateSystem<EndSimulationEntityCommandBufferSystem>();
9.         random = new Unity.Mathematics.Random(493824);
10.     }
11.  
12.     protected override void OnUpdate()
13.     {
14.         var rand = random;
15.         float dt = Time.DeltaTime;
16.         var ecb = m_EndSimulationEcbSystem.CreateCommandBuffer().ToConcurrent();
17.         Entities
18.             .ForEach((Entity entity, int entityInQueryIndex, ref SpawnDelayComponent spawnDelay, in ZombiePrefabComponent zombiePrefab) =>
19.             {
20.                 spawnDelay.currentTime += dt;
21.                 if (spawnDelay.currentTime > spawnDelay.delayTime)
22.                 {
23.                     spawnDelay.currentTime = 0f;
24.  
25.                     Entity spawnedEntity = ecb.Instantiate(entityInQueryIndex, zombiePrefab.prefabEnity);
26.                     float nextRandom = rand.NextFloat(-5f, 5f);
27.                     var newPosition = new float3(-10f, nextRandom, 0);
28.                     Debug.Log(nextRandom);
29.                     ecb.AddComponent<Translation>(entityInQueryIndex, spawnedEntity, new Translation
30.                     {
31.                         Value = newPosition
32.                     });
33.  
34.                     var newRotation = quaternion.identity;
35.                     ecb.AddComponent<Rotation>(entityInQueryIndex, spawnedEntity, new Rotation
36.                     {
37.                         Value = newRotation
38.                     });
39.  
40.                     ecb.AddComponent(entityInQueryIndex, spawnedEntity, new LocalToWorld
41.                     {
42.                         Value = new float4x4(newRotation, newPosition)
43.                     });
44.                 }
45.             })
46.             .Schedule();
47.         m_EndSimulationEcbSystem.AddJobHandleForProducer(this.Dependency);
48.     }
49. }

 

Because it's struct and pass by value. After call NextXXX you should pass random back. You can use something like that and have predifined set of randoms per thread and use that static array inside your jobs.

Code (CSharp):

1. /// <summary>
2.     /// Utility system which populates and handle disposing for game randoms
3.     /// </summary>
4.     [UpdateInGroup(typeof(InitializationSystemGroup))]
5.     public class RandomsUtilitySystem: SystemBase
6.     {
7.         /// <summary>
8.         /// Array of randoms
9.         /// </summary>
10.         /// <remarks>
11.         /// Use [NativeDisableParallelForRestriction] attribute for this array in your jobs for write back<br/>
12.         /// Use [NativeSetThreadIndex] _nativeThreadIndex as indexer for that array
13.         /// </remarks>
14.         public static NativeArray<Unity.Mathematics.Random> Randoms;
15.  
16.         [ExcludeFromDocs]
17.         protected override void OnCreate()
18.         {
19.             Randoms = new NativeArray<Unity.Mathematics.Random>(JobsUtility.MaxJobThreadCount, Allocator.Persistent, NativeArrayOptions.UninitializedMemory);
20.             var r = (uint) UnityEngine.Random.Range(int.MinValue, int.MaxValue);
21.             for (int i = 0; i < JobsUtility.MaxJobThreadCount; i++)
22.                 Randoms[i] = new Unity.Mathematics.Random(r == 0 ? r + 1 : r);
23.             Enabled = false;
24.         }
25.      
26.         [ExcludeFromDocs]
27.         protected override void OnDestroy()
28.         {
29.             if (Randoms.IsCreated)
30.                 Randoms.Dispose();
31.         }
32.      
33.         [ExcludeFromDocs]
34.         protected override void OnUpdate() {}
35.     }

Usage

Code (CSharp):

1. private struct SomeJob : IJobParallelFor
2.         {
3.             [NativeDisableParallelForRestriction] public  NativeArray<Random> Randoms;
4.             [NativeSetThreadIndex]                private int                 _nativeThreadIndex;
5.  
6.             public void Execute(int                         index)
7.             {
8.                 var random = Randoms[_nativeThreadIndex];
9.              
10.                 //... Do stuff like random.NextInt(0, 100);
11.              
12.                 // return back
13.                 Randoms[_nativeThreadIndex] = random;
14.             }
15.         }

 

Thank you. I see your post in another thread about random, but when i see "NativeDisableContainerSafetyRestriction" - i begin reading about it and im scared
Documentation tells:
WithNativeDisableContainerSafetyRestriction(myvar) — disables normal safety restrictions that prevent dangerous access to the native container. Disabling safety restrictions unwisely can lead to race conditions, subtle bugs, and crashes in your application.

Now i understand that is only one thread read and write only 1 element of native erray at same time because of [NativeSetThreadIndex], and this operation is safe.

 

Yes

 

I can use RandomsUtilitySystem.Random only with IJobParallelFor or i can i use it in regular Entities.ForEach().ScheduleParallel() ?

I can throw "[NativeDisableParallelForRestriction] public NativeArray<Random> Randoms;" using WithNativeDisableParallelForRestriction(myvar). Is there any way to throw "[NativeSetThreadIndex] private int _nativeThreadIndex;" into Entities.ForEach of SystemBase?

 

https://docs.unity3d.com/Packages/c...ntities_foreach.html#special-named-parameters