Pure ECS and transform.forward vector

How does one get access to the forward vector for a pure ECS system?

 

well I was reading the source the other day and i found nothing this superfluous on the transform system.
So if you really want a forward vector on some entities, just make a component that holds it and a system that updates it

 

I also ran across Math.forward(). . . . where you provide a quaternion

 

transform.forward is simply quaternion * vector.forward, which in this case is transform.rotation * Vector3 (1,0,0) Vector3 (0,0,1).

Then need of course put that into ECS representation.

 

Vector3.forward is (0,0,1)

 

Ops yes, sorry my wrong. Thx for correction. I must be dreaming about something else

 

I mean, it's technically forward. In the 2D XY plane space defined by basis vectors (0,1,0 ) and (1,0,0).

 

For anyone reading this now, I saved a camera reference into a IComponentData and used that to define a transform.forward

 

How would one add a reference to the Camera class inside IComponentData? I thought you can only add primitive/bittable types to IComponentData.

 

You can make an IComponentData class and use it as a usual IComponentData struct.
The only thing is that you can only use it on the main thread so all your "job" have to run instead of schedule and also you can't use burst.
So it may be convenient but it's definitely not 'DOTS' performant.

 

Thanks for the quick reply. When I try adding a Camera class to an IComponentData struct, I get "ArgumentException: Component contains a field of UnityEngine.Camera, which is neither primitive nor blittable." Am I missing something?

 

make sure its a class not a struct ie

public class MyComponent : IComponentData

 

Not sure what all this business with the camera is about but for an entity's forward vector you can do:

Code (CSharp):

1. public class MoveForwardSystem : SystemBase
2. {
3.     protected override void OnUpdate()
4.     {
5.         float dt = Time.DeltaTime;
6.         Entities.ForEach((ref Translation t, in LocalToWorld ltw) =>
7.         {
8.             t.Value += ltw.Forward * dt;
9.         }).Schedule();
10.     }
11. }

I think that's what at least some of you are looking for?

 

This needs to be marked at the answer to the original question. Clean, straight to the point, no bs. Well done Sarkahn, and thank you.

 

I SPENT SO LONG LOOKING FOR AN ANSWER thank you so much!!!

 

Thank you so much for the answer. You saved me lot of time.

 

I like to use math.mul(rotation, direction). But you can use math.forward(rotation) which basically uses math.mul internally I believe.

Code (CSharp):

1. Entities.ForEach((ref Rotation rotation) =>
2.         {
3.             // Forward vector = float3(0f, 0f, 1f)
4.             float3 forward = math.mul(rotation.Value, new float3(0f, 0f, 1f));
5.  
6.             // You can also use math.forward(rotation)
7.             forward = math.forward(rotation.Value);
8.         }).Run();