Trying To Understand SetComponentData

Hello,

I am trying to understand how to use the EntityManager to create new components. I will be doing a lot of this in my game as it is a classic RTS style. Right now I am just trying to practice with a building.

My initial scene contains the prefab 'Building'






And my bootstrap has the following code:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using Unity.Entities;
5. using UnityEngine.AI;
6. using Unity.Transforms;
7. using static BuildingProductionSystem;
8.  
9. public class FallenBootstrap  {
10.     public static EntityManager entityManager;
11.     private static EntityArchetype cameraArchetype;
12.     private static EntityArchetype buildingArchetype;
13.     private static EntityArchetype unitArchetype;
14.     private static EntityArchetype groundArchetype;
15.  
16.    
17.     // Use this for initialization
18.     [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
19.     public static void Start () {
20.         Debug.Log("I have started the game!");
21.         entityManager = World.Active.GetOrCreateManager<EntityManager>();
22.  
23.         cameraArchetype = entityManager.CreateArchetype(typeof(Rotation), typeof(Position), typeof(Camera));
24.  
25.  
26.         buildingArchetype = entityManager.CreateArchetype(typeof(MeshRenderer), typeof(BoxCollider), typeof(BuildingInputSystem),
27.             typeof(RectTransform), typeof(MeshFilter), typeof(MouseOverSystem), typeof(Position));
28.  
29.         unitArchetype = entityManager.CreateArchetype(typeof(MeshRenderer), typeof(SphereCollider), typeof(NavMeshAgent));
30.  
31.         groundArchetype = entityManager.CreateArchetype(typeof(MeshRenderer), typeof(MeshCollider));
32.  
33.         Entity building = entityManager.CreateEntity(buildingArchetype);
34.  
35.         var proto = GameObject.Find("Building");
36.         var proto_position = proto.GetComponent<Position>().Value; //why are these different?
37.         var proto_rect_transform = proto.GetComponent<RectTransform>();
38.         Object.Destroy(proto);
39.  
40.         entityManager.SetComponentData(building, proto_position);
41.        
42.  
43.      //   var Camera = entityManager.CreateEntity(cameraArchetype);
44.    
45.     }
46.    
47. }
48.  

You can see when I do this I get the following exception:


It reads: "The type 'Unity.Mathematics.float3' cannot be used as type parameter 'T' in the generic type or method 'EntityManager.SetComponentData<T>(Entity, T)'. There is no boxing conversion from 'Unity.Mathematics.float3' to 'Unity.Entities.IComponentData'.

In the TwoStick Pure example they do something similar where they get the playerLook from the mesh, but I do see how they are doing something like

entityManager.AddSharedComponentData(player, PlayerLook);


Does my data have to be shared? What should I be doing to convert the prefab position into a ComponentData?

Thank you in advance.

 

SetComponentData

has to be used with a whole component. It does not know if this float should go into

Position

IComponentData

on the entity. Instead, you have to add

new Position { Value = proto_position }

Another issue, after this error it should say this entity does not have a component of type

Position

so you cannot use Set (but you can use

AddComponentData

) A

Position

component is not magically added for all generated entity from

GameObjectEntity

nor magically converted from object's transform (But you do magically get

TransformAccess

from object's transform), you have to manually add them so

GameObjectEntity

can bundle it together at the time it creates an entity. Add a

MonoBehaviour

named

PositionComponent

for this, and now you can use

SetComponentData

because your entity has

Position

data of 0,0,0

To not having 0,0,0 but instead prefab position in this

Position

component data additionally add

MonoBehaviour

named

CopyInitialTransfromFromGameObject

. Or if you want the

Position

in entity be continuously updated to match your game object use the one without Initial.

 

Thank you very much for your response. I made a couple changes.

I changed it to AddComponentData and did the New Position etc...., also I was trying to call GameObject.Find on a prefab when I really needed to "break" my prefab and turn it into a normal game object. However, when I call find on it I still get a null pointer reference. Running this code:

Code (CSharp):

1. var proto = GameObject.Find("BuildingPrototype");
2.         if(proto == null)
3.         {
4.             Debug.Log("why?");
5.         }
6.         var proto_position = proto.GetComponent<Position>().Value; //why are these different?
7.         var proto_rect_transform = proto.GetComponent<RectTransform>();
8.         Object.Destroy(proto);

will result in "why?" being printed out. Here is my building prototype:



any thoughts as to why that is? thank you for your time.

 

Whoa! I am a noob. Sorry but I realized the reason I didn't find the object is this line!


[RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]

I see no reason to not change it to AfterSceneLoad so... fixed that problem. On to the next =).

 

Note that you can have two separate methods, one marked with BeforeSceneLoad and another marked with AfterSceneLoad, coexisting in the same class.