ECS RenderMesh not visible

Questions & Answers
1

Hello,

I’ve made a simple script for ECS and Hybrid Renderer, everything works fine except RenderMesh which do not render at all.

public class GameManager : MonoBehaviour
{
    public Mesh newMesh;
    public Material newMaterial;
    void Start()
    {
        EntityManager manager = World.DefaultGameObjectInjectionWorld.EntityManager;
        EntityArchetype archetype = manager.CreateArchetype(typeof(LocalToWorld), typeof(RenderMesh), typeof(Translation));
        Entity entity = manager.CreateEntity(archetype);
        manager.SetSharedComponentData<RenderMesh>(entity, new RenderMesh
        {
            mesh = newMesh,
            material = newMaterial,
            subMesh = 0,
            layer = 0,
            castShadows = ShadowCastingMode.On,
            receiveShadows = true
        });
    }
}
2

Hey mate,

If you are trying this one on newer versions of unity (2019.3.x), you NEED to add typeof(RenderBounds) to your archetype. Without this IT WILL NOT DISPLAY.

Best regards

3

Most common issues:

  • Missing components

If you open up an Entity Debugger ( Systems since entities v 0.50 ) window it will list all component types that systems look for (aka “entity query”). If an Entity doesn’t match that list (query) - entity is simply ignored. And this is exactly what happens here.

Note: some specific components are added automatically by systems when criteria is met. For example: adding Translation or/and Rotation to an entity will result in LocalToWorld being added as well. Adding RenderBounds and LocalToWorld will result in WorldRenderBounds being added.

190702-screenshot-2022-01-02-195051.jpg
190702-screenshot-2022-01-02-195051.jpg1163×181 41.1 KB

  • RenderBounds with zero size. You can identify this case in cases where mesh is visible ONLY while it’s world position (mesh origin) is visible to the camera and whole disappears immediately when it goes off screen.

  • WorldRenderBounds with not encapsulating the mesh properly. This is caused by RenderBounds being offset or not sized properly i.e. it’s not zero but it’s not correct either.
    It’s harder to investigate this case because meshes can be totally invisible or appear/hide for no apparent reason when camera moves. I strongly suggest you install this package, as it allows you to select entities and see their WorldRenderBounds in the Scene window:
    GitHub - JonasDeM/EntitySelection: A minimal solution for selecting entities in the unity sceneview. Useful for users using older versions of the Unity entities package.

  • Render Pipeline-specific components are missing because URP and HDRP require different data sets to work properly. This often results in meshes being black or not affected by lights. Fix: use RenderMeshUtility (see code sample below).
    _

TL;DR:

Here is a preferable workflow to create mesh entities. It adds all required components and initializes their values properly.

using UnityEngine;
using UnityEngine.Rendering;
using Unity.Entities;
using Unity.Rendering;
using Unity.Transforms;
using Unity.Mathematics;
using Random = UnityEngine.Random;
public class LetsCreateARenderMeshEntity : MonoBehaviour
{
	[SerializeField] Mesh _mesh = null;
	[SerializeField] Material _material = null;
	void Start ()
	{
		var entityManager = World.DefaultGameObjectInjectionWorld.EntityManager;

		Entity prefab = entityManager.CreateEntity( typeof(Prefab) );// prefab is invisible & inactive
		RenderMeshUtility.AddComponents( prefab , entityManager , new RenderMeshDescription(
			mesh:_mesh , material:_material , shadowCastingMode:ShadowCastingMode.On , receiveShadows:true
		) );

		for( int i=0 ; i<1000 ; i++ )
		{
			float3 position =  Random.insideUnitSphere * new float3( 100f , 100f , 100f );
			quaternion rotation = quaternion.Euler( 0f , 0f , 0f );
			float3 scale = Vector3.one;
			Entity instance = entityManager.Instantiate( prefab );
			entityManager.SetComponentData( instance , new LocalToWorld{
				Value = float4x4.TRS( position , rotation , scale )
			} );
		}
	}
}