Resolved How to Update MaterialMeshInfo from IJobEntity

I am trying to dynamically generate modifiable terrain within a system. I have a general outline to generate the meshes using the MeshDataAPI, create a MaterialMeshInfo from each meshID, and then update the MaterialMeshInfo IComponentData of the entity in question using the ECB.

After generating the NativeArray of meshIDs, I run this job:

Code (CSharp):

1. public partial class SectorMeshingSystem : SystemBase
2. {
3.     protected override void OnUpdate()
4.     {
5.         var ecb = new EntityCommandBuffer(Allocator.TempJob);
6.  
7.         // ... Other code to generate meshIDs and MaterialID
8.  
9.         new ApplyMeshJob
10.         {
11.             ecb = ecb,
12.             meshIDs = meshIDs,
13.             materialID = materialID
14.         }.Run();
15.  
16.         ecb.Playback(EntityManager);
17.     }
18. }
19.  
20. public partial struct ApplyMeshJob : IJobEntity
21. {
22.     public EntityCommandBuffer ecb;
23.     public NativeArray<BatchMeshID> meshIDs;
24.     public BatchMaterialID materialID;
25.  
26.     private void Execute([EntityIndexInQuery] int i, SectorMeshAspect sectorMeshAspect)
27.     {
28.         var materialMeshInfo = new MaterialMeshInfo {
29.             MaterialID = materialID, MeshID = meshIDs[i]
30.         };
31.         ecb.SetComponent<MaterialMeshInfo>(sectorMeshAspect.Entity, materialMeshInfo);
32.     }
33. }

I don't know where I'm going wrong. I read from another post that you should be able to update the MaterialMeshInfo component directly in runtime and update the mesh, though I could be misunderstanding what JussiKnuuttila was saying (https://forum.unity.com/threads/rendermeshutility-will-not-accept-entitycommandbuffer.1370682/)

Do I need to use RenderMeshUtility.AddComponents(...) for this anyways?

 

I have the entities set to initially have a standard cube mesh, which I then update with this. The cube mesh is correctly disappearing, but the new mesh I'm applying (the Tetrahedron mesh described here: https://docs.unity3d.com/2020.1/Documentation/ScriptReference/Mesh.MeshData.html) is not showing.
So, technically it seems the entities are not rendering at all.
I have verified that the Mesh object is indeed populated with the correct vertices and indices.

The transform is correct as well, I gave it a scale of 12 and positioned it (0, 0, -12)

It seems like the MaterialMeshInfo is also being properly updated:

 

Update:
I found out that my issue with the above situation was solely because I was using a bad material.

Bad material:

Material newMaterial = new Material(Shader.Find("Specular"));

Working material:

Material newMaterial = new Material(Shader.Find("Universal Render Pipeline/Lit"));

Thank you so much JussiKnuuttila for helping me isolate the problem. It's great to have a sanity check that I was doing the new process correctly.