How do you set non-local rotation in ECS? (also: documentation feedback)

Hi, really quick question: how do you set the global rotation of an entity in ECS? It seems that the Rotation component always sets the equivalent of transform.localRotation, while I'm looking for transform.rotation.

Also, some documentation feedback: I spent a good 15 or 20 minutes reading over the Transforms documentation for ECS trying to answer this question, and while I feel like I understand what's going on under the hood better now, I think this page could be really improved by adding just a few examples of how things map from the MonoBehaviour world, like "hey, remember transform.localPosition? Now it's called Translation!", etc.

 

Just use Rotation Component instead.
You can use for example

Code (CSharp):

1. GetComponentDataFromEntity <Rotation> () ;

 

Set world rotation - multiply your world rotation to inversed LocalToWorld matrix associated with entity
Get world rotation - multiply rotation from Rotation component to LocalToWorld matrix associated with entity

 

@Antypodish The Rotation component sets local rotations, not world-space rotation

@eizenhorn Do you mean multiply the entire matrix by the quaternion? Because that gives me some freaky effects and changes scale and stuff.

I'm basically trying to translate this code from Unity:

Code (CSharp):

1. transform.rotation = Quaternion.LookRotation(target.position - transform.position, Vector3.up);
2.  

I tried multiplying by LocalToWorld like this but it didn't go well:

Code (CSharp):

1. rotation.Value = math.mul(
2.     math.inverse(localToWorld.Value),
3.     quaternion.LookRotationSafe(rotationData.TargetPosition - rotationData.SourcePosition, Vector3.up).value);

Or is there some specific element of LocalToWorld which holds the parent rotation?

 

@dthurn are yo on Unity 2018, or 2019?

Makes really no sense to me, if that what is happening. My understanding was, that transform.localRotation meant to be strictly for local rotation.

 

No. Simple multiplication it’s for translation. For rotation you also use sum/subtract of sin cos per axis.

 

Could you post a code snippet demonstrating getting a global rotation from LocalToWorld? I am struggling to make it work.

 

Code (CSharp):

1.  Quaternion.LookRotation(localToWorld.Forward, localToWorld.Up)

As to the answer of the topic's question;
For an entity without a parent you can set the rotation to the world rotation and then you need to recalculate the LocalToWorld matrix. This can be done by creating a new float4x4 matrix from the Translation and Rotation values.

For an entity _with_ a parent you also need to update the LocalToParent matrix which is more involved. You will need to get the parent's LocalToWorld matrix, calculate the position and rotation difference and use those to define the Rotation and Translation, and then create a new LocalToParent and LocalToWorld matrix.

In both cases if the entity you're setting the world rotation for also has children you'll need to recurse through them to update their LocalToWorld matrices.

You can find an example of all of the above here: https://forum.unity.com/threads/how-to-set-nested-translation-to-world-position.756224/#post-5059022

 

for everybody else who searches a way to get the localRotation as WorldRotation in ECS jobs:

Code (CSharp):

1. public static quaternion GetWorldRotation(LocalToWorld ltw)
2.     {
3.         return quaternion.LookRotationSafe(ltw.Forward, ltw.Up);
4.     }

this bit made my day hell

 

any direct solution to configure world rotation?

 

why not just

Code (CSharp):

1. var worldRotation = new quaternion(localToWorld.Value);

also to set

Code (CSharp):

1. var localToWorld = new LocalToWorld
2.             {
3.                 Value = float4x4.TRS(translation, rotation, scale)
4.             };

 

thank you @thelebaron, now already know a way to follow!