ECS: multiple materials? - SOLVED.

Unity Engine
,
1

I have some trees that have a single mesh and multiple materials (bark and leaves) I am attempting to line my streets with trees in ECS, but I can’t figure out how to apply a second material.

On Reddit someone mentioned the subMesh value, but this is just an int. If I set that to 1 and then apply the second material, ONLY the second material is shown. So obviously I am doing something wrong

int randomValue = UnityEngine.Random.Range(0, treesComponentList.Count);
Mesh propMesh = treesComponentList[randomValue].mesh;
Material propMaterial = treesComponentList[randomValue].materials[0];

RenderMesh renderMesh = new RenderMesh();
renderMesh.material = propMaterial;
renderMesh.mesh = propMesh;

renderMesh.subMesh = 1;
renderMesh.material = treesComponentList[randomValue].materials[1];

2

You’ll need two RenderMesh instances, one for each submesh and material.

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3

Ok, sounds logical. So specifically how is this achieved? My current archetype is:
EntityArchetype entityArchetype = entityManager.CreateArchetype(
typeof(SidewalkTreeTag),
typeof(Translation),
typeof(RenderMesh),
typeof(Scale),
typeof(LocalToWorld)
);

//I attempted to get this working like this:
Entity entity = entityManager.CreateEntity(entityArchetype);
entityManager.SetComponentData(entity, new Translation { Value = position });
entityManager.SetComponentData(entity, new Scale { Value = treeScale });
entityManager.SetSharedComponentData(entity, new RenderMesh { mesh = propMesh, material = propMaterial, subMesh = 0 });

if (treesComponentList[0].materials.Count > 1)
{
entityManager.AddComponent(entity, typeof(RenderMesh));
entityManager.SetSharedComponentData(entity,
new RenderMesh {
mesh = propMesh,
material = treesComponentList[randomValue].materials[1],
subMesh = 0 });
}

I tried setting the subMesh to 0 and to 1, in each case I still end up with just the Bark showing on the tree (the bark is the first material in the list. So, it seems that I am setting the first RenderMesh, and not the second… or, well, I just don’t know. Care to enlighten me? Slap me and say; “hey stupid, it’s like this:” I’m ok with that.

4

Use two children entities each with a RenderMesh. You’ll probably want to instantiate from a prefab rather than an archetype for this.

5

You should create another entity and set RM. You can’t have many IComponentData\ISharedComponentData on the same entity.
Edit: Ah @DreamingImLatios already answered, I’m not updated page :slight_smile:

6

Ok, I’m going to have to be annoying. (SO sorry) But is there an example of this?

It sounds like I should create one entity, and that holds what, just two child entities? I would think you are saying I add two child entities to that entity and add the RenderMesh component to each of the child components, right?

I always work best when I can see an example, and I will be giving the above idea a try right. I am attempting to do the above idea, but I’m just not getting there. Feel free to point and laugh.

7

No, you need only two entities for this case. Just look at how conversion workflow works, look at unity samples github and inspect which components parent and child entities have. Spoiler - Parent component data, Child buffer, LocalToParent component data etc.

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8

So correct me if I am wrong (PLEASE!) I don’t need a parent, but each material is going to need a new entity. I just got the code working like this:

for (int p = 0; p < treesComponentList[randomValue].materials.Count; p++)
{
Entity entity = entityManager.CreateEntity(entityArchetype);
entityManager.SetComponentData(entity, new Translation { Value = position });
entityManager.SetComponentData(entity, new Scale { Value = treeScale });
entityManager.SetSharedComponentData(
entity,
 new RenderMesh {
 mesh = propMesh,
  material = treesComponentList[randomValue].materials[p],
  subMesh = p });
}

because of this I have two entities for one tree, is this correct?

9

If it looks like you want, why not? :slight_smile: If your threes shouldn’t be in hierarchy (for example they wouldn’t move like some solid thing) it’s fine without parenting

1 Like
10

Thank you all for the helpful info.

In hopes this helps the next person, here is my code for taking a list of IComponentData, shown in the inspector, to draw at startup

using System.Collections.Generic;
using UnityEngine;

[System.Serializable]
public struct MeshMaterialsComponents
{
    public Mesh mesh;
    public List<Material> materials;
}

which is used like this

[Header("Sidewalk Trees")]
    [SerializeField]
    private List<MeshMaterialsComponents> treesComponentList = new List<MeshMaterialsComponents>();

Then I have a function that loads just trees (I’m using Easy Roads 3D, a great asset with lots of data available via it’s api) With that I look through all roads, get their data points and loop through those to add trees

float treeScale = UnityEngine.Random.Range(0.8f, 1.2f);
int randomValue = UnityEngine.Random.Range(0, treesComponentList.Count);
Vector3 translation = DistanceBetweenPoints(markersSide[i], markersCenter[i], treeOffset);translation.y += propYOffset;

                    for (int p = 0; p < treesComponentList[randomValue].materials.Count; p++)
                    {
                        Entity entity = entityManager.CreateEntity(entityArchetype);
                        entityManager.SetComponentData(entity, new Translation { Value = translation });
                        entityManager.SetComponentData(entity, new Scale { Value = treeScale });
                        entityManager.SetSharedComponentData(
                            entity,
                            new RenderMesh {
                                mesh = treesComponentList[randomValue].mesh,
                                material = treesComponentList[randomValue].materials[p],
                                subMesh = p });
                    }
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