Is it possible to use Hybrid and Pure at the same time?

So my goal is simple: I have a Player Entity (Pos, Rot, Speed, Player) and I'd like to have a Camera that follows the player entity. The player controls the player entity via a simple input system. I just want to make the camera follow the player entity position.

I was able to do it using Hybrid approach but no luck with Pure, probably because of my lack of understanding.

I searched the forums and I found these statements:

1. Don't use Camera with ECS because I won't be instantiating hundreds of cameras... but I disagree because I'd like to use the same architecture everywhere in my game and squeeze perf benefits as much as possible.

2. Camera is still a game object and because of that it is not yet supported in Pure ECS.

So I thought: Well, I could make the Player entity part with Pure ECS and then do Hybrid ECS for the Camera system but I can't get it to work. When I try to access the Player entity position, I keep getting errors about transform pointers:

Position must be an unsafe pointer to the Unity.Transforms.Position. Like this: Unity.Transforms.Position* Position;

Before I go even further, I'd like to know if this is even possible. Any help is appreciated.

 

Yes it works fine. I'd need to see some code to see what you're doing wrong.

 

The code is below. I'm sure I'm missing something:

Code (CSharp):

1.  
2. using System.Collections;
3. using System.Collections.Generic;
4. using Pure.Components;
5. using Unity.Entities;
6. using Unity.Mathematics;
7. using Unity.Transforms;
8. using UnityEngine;
9. public class PlayerCameraSystem : ComponentSystem
10. {
11.     private struct EntityCamera
12.     {
13.         public readonly int Length;
14.         public GameObjectArray GameObject;
15.         public ComponentDataArray<PlayerCamera> PlayerCamera;
16.         public ComponentDataArray<Position> Position;
17.         public ComponentDataArray<Rotation> Rotation;
18.     }
19.     private struct EntityPlayer
20.     {
21.         public readonly int Length;
22.         public GameObjectArray GameObject;
23.         public ComponentDataArray<Player> Player;
24.         public ComponentDataArray<Position> Position;
25.     }
26.     [Inject] private EntityCamera _entityCamera;
27.     [Inject] private EntityPlayer _entityPlayer;
28.     protected override void OnUpdate()
29.     {
30.         if (_entityCamera.Length == 0 || _entityPlayer.Length == 0)
31.         {
32.             Debug.Log("--- NOPE ---");
33.             Debug.Log(_entityCamera.Length); // 1
34.             Debug.Log(_entityPlayer.Length); // 0
35.             return;
36.         }
37.         for (int i = 0; i < _entityPlayer.Length; ++i)
38.         {
39.             float3 currentPos = _entityCamera.Position[i].Value;
40.             float3 desiredPos = _entityPlayer.Position[i].Value + new float3(0, 18f, -10f);
41.             float3 smoothedPos = math.lerp(currentPos, desiredPos, 10f * Time.deltaTime);
42.             Position cameraPos = _entityCamera.Position[i];
43.             cameraPos.Value = smoothedPos;
44.             quaternion rotation = quaternion.LookRotation(_entityPlayer.Position[i].Value - currentPos, math.up());
45.             Rotation cameraRot = _entityCamera.Rotation[i];
46.             cameraRot.Value = math.slerp(_entityCamera.Rotation[i].Value, rotation, Time.deltaTime * 0.25f);
47.         }
48.     }
49. }
50.  

I keep getting a 0 length _entityPlayer. The EntityPlayer is the one I'm creating with pure ECS:

Code (CSharp):

1. Entity playerEntity = EntityManager.CreateEntity(PlayerArchetype);
2.             EntityManager.SetComponentData(playerEntity, new Position() { Value = new float3(0f, 1f, 0f) });
3.             EntityManager.SetComponentData(playerEntity, new Rotation() { Value = quaternion.identity });
4.             EntityManager.SetComponentData(playerEntity, new PlayerInput() { Horizontal = 0, Vertical = 0, MousePosition = float2.zero });
5.             EntityManager.SetComponentData(playerEntity, new MoveSpeed() { Value = 6 });
6.             EntityManager.AddSharedComponentData(playerEntity, PlayerLook);

 

The pure entity has no game object attached yet you're requiring a GameObjectArray so you're never going to get a player match.

 

Yes, thanks for pointing it out, it was obvious but I couldn't see it.

I also realized I can't really modify position like that for my Camera, I need to do something like:

Code (CSharp):

1. _entityCamera.Position[i] = new Position { Value = smoothedPos }

That updates the Position Component but it doesn't work for Hybrid components. As far as I understand, the game object still uses the old Transfom which controls the position of my camera, so I need to update it via transform, correct?

So this is what worked for me:

Code (CSharp):

1. private struct EntityCamera
2.     {
3.         public readonly int Length;
4.         public GameObjectArray GameObjects;
5.         public ComponentDataArray<PlayerCamera> PlayerCameras;
6.     }
7.  
8.     private struct EntityPlayer
9.     {
10.         public readonly int Length;
11.         public ComponentDataArray<Player> Player;
12.         public ComponentDataArray<Position> Position;
13.     }
14.  
15.     [Inject] private EntityCamera _entityCamera;
16.     [Inject] private EntityPlayer _entityPlayer;
17.  
18.     protected override void OnUpdate()
19.     {
20.         if (_entityCamera.Length == 0 || _entityPlayer.Length == 0) return;
21.  
22.         float deltaTime = Time.deltaTime;
23.  
24.         for (int i = 0; i < _entityPlayer.Length; ++i)
25.         {
26.             GameObject cameraGO = _entityCamera.GameObjects[i];
27.  
28.             float3 currentPos = cameraGO.transform.position;
29.             float3 desiredPos = _entityPlayer.Position[i].Value + new float3(0, 18f, -10f);
30.             float3 smoothedPos = math.lerp(currentPos, desiredPos, 10f * deltaTime);
31.             cameraGO.transform.position = smoothedPos;
32.  
33.             Quaternion currentRot = cameraGO.transform.rotation;
34.             Quaternion desiredRot = Quaternion.LookRotation(_entityPlayer.Position[i].Value - currentPos, math.up());
35.             Quaternion smoothedRot = math.slerp(currentRot, desiredRot, deltaTime);
36.             cameraGO.transform.rotation = smoothedRot;
37.         }
38.     }

I posted my solution here in case anyone has any issues with this in the future.

 

You can just add the, CopyTransformToGameObject component, to the hybrid object and the gameobject transform will be updated automatically when you make changes to the position/rotation components.

 

Have you run into cases where you want ECS to access more than just transform?

 

This is good, but I found that it won't respect the NavMesh using this.

 

I don't actually use hybrid anymore [at least I use no GameObjectEntity] as I ended up converting my entire project to pure.

The only components I still need access to are stuff like, Camera, Light etc. Originally I add these as shared components but now I just add them directly as objects to the entity just like GameObjectEntity does for transform etc (this requires a little reflection because the methods are internal.)

I also wrote a couple of wrapper systems for third party tools such as a CineMachine.Hybrid system etc.

If you're using navmesh you probably want to go the other way (CopyTransformFromGameObject) and drive your entity position/rotation from the navmesh.