How to rotate a cube from within a component system?

Hi all,

I'm trying to learn ECS by trial and error. I'm looking at various code samples, documentation and youtube videos. I'm just messing around with the pure ECS approach. I've got an entity archetype that has a position and rotation. It renders as a cube. I've got a rotation system that I am just trying to make the cube constantly rotate in place. I've looked at the rotation sample code, from the official unity sample repo, but when I replicate the math logic for rotating I get run-time errors (something about invalid AABB result).

Here is the code for my rotation system. Any idea what I'm doing wrong here? I'm not using the job component system.

Code (CSharp):

1. using UnityEngine;
2. using Unity.Entities;
3. using Unity.Transforms;
4. using Unity.Mathematics;
5.  
6. namespace CubeWorld.Systems
7. {
8.     public class PlayerRotationSystem : ComponentSystem
9.     {
10.         [Inject]
11.         private PlayerRotationSystemData m_data;
12.  
13.         #region Methods
14.  
15.         protected override void OnUpdate()
16.         {
17.             var time = Time.deltaTime;
18.  
19.             for (var i = 0; i < m_data.Length; i++)
20.             {
21.                 var rotation = m_data.Rotations[i];
22.  
23.                 m_data.Rotations[i] = new Rotation
24.                 {
25.                     Value = math.mul(math.normalize(rotation.Value), quaternion.AxisAngle(math.up(), 20 * time))
26.                 };
27.             }
28.         }
29.  
30.         #endregion
31.     }
32.  
33.     public struct PlayerRotationSystemData
34.     {
35.         #region Values
36.  
37.         public readonly int Length;
38.         public ComponentDataArray<Rotation> Rotations;
39.  
40.         #endregion
41.     }
42. }
43.  

I've tried other equations too, but none have managed to get the cube to rotate.

 

I think you're missing to tell the entityManager to set your components data. Try something like:

Code (CSharp):

1.             var time = Time.deltaTime;
2.             var entityManager = World.Active.GetOrCreateManager<EntityManager>();
3.             for (var i = 0; i < m_data.Length; i++)
4.             {
5.                 var rotation = m_data.Rotations[i];
6.                 var entityWithRotation = m_data.Entities[i];
7.                 var newRotation = new Rotation
8.                 {
9.                     Value = math.mul(math.normalize(rotation.Value), quaternion.AxisAngle(math.up(), 20 * time))
10.                 };
11.  
12.                 PostUpdateCommands.SetComponent(entityWithRotation, newRotation);
13.             }
14.         }

You've got to add: [ReadOnly] public EntityArray Entites; to your PlayerRotationSystemData too.

 

Hmm. OK. I added that new EntityArray and am using PostUpdateCommands. I'm just getting a bunch of errors when I run it. Errors mostly regarding the following ...

Code (CSharp):

1. Invalid AABB result
2. UnityEngine.Graphics:DrawMesh(Mesh, Matrix4x4, Material, Int32, Camera, Int32, MaterialPropertyBlock, ShadowCastingMode, Boolean)
3. Unity.Rendering.MeshInstanceRendererSystem:RenderBatch(Int32, Int32) (at Library/PackageCache/com.unity.entities@0.0.12-preview.19/Unity.Rendering.Hybrid/MeshInstanceRendererSystem.cs:643)
4. Unity.Rendering.MeshInstanceRendererSystem:UpdateDynamicInstanceRenderer() (at Library/PackageCache/com.unity.entities@0.0.12-preview.19/Unity.Rendering.Hybrid/MeshInstanceRendererSystem.cs:618)
5. Unity.Rendering.MeshInstanceRendererSystem:OnUpdate() (at Library/PackageCache/com.unity.entities@0.0.12-preview.19/Unity.Rendering.Hybrid/MeshInstanceRendererSystem.cs:825)
6. Unity.Entities.ComponentSystem:InternalUpdate() (at Library/PackageCache/com.unity.entities@0.0.12-preview.19/Unity.Entities/ComponentSystem.cs:374)

 

With ComponentDataArray the write back to ECS is allowed, you don't really need to tell EntityManager to set data.

Do you have MeshInstanceRenderer component in your archetype with mesh and material? Also preview 19 ECS has several bugs regarding to TransformSystem.

https://issuetracker.unity3d.com/issues/ecs-disabling-a-transform-system-component-resets-its-values
https://issuetracker.unity3d.com/is...nsform-system-goes-into-a-running-update-loop

 

I do have the mesh instance renderer - I'm using the prefab approach, and it's my understanding that when I add the mesh instance renderer to the prefab and then pull components off the prefab that the mesh instance renderer is included due to that.

OK. I'll try downgrading. I'm using the 2019 alpha.

 

I think what I'm experiencing is the bug you linked at https://issuetracker.unity3d.com/is...nsform-system-goes-into-a-running-update-loop

 

Actually, I'm not experiencing that issue. The `math.normalize` method was just returning NaN. I had to instead use `math.normalizesafe`.

Code (CSharp):

1. protected override void OnUpdate()
2. {
3.     var time = Time.deltaTime;
4.  
5.     for (var i = 0; i < m_data.Rotations.Length; i++)
6.     {
7.         var current = m_data.Rotations[i].Value;
8.         var desired = math.mul(math.normalizesafe(current), quaternion.AxisAngle(math.up(), time));
9.  
10.         m_data.Rotations[i] = new Rotation { Value = desired };
11.     }
12. }