What is the replacement for transform hierarchy?

So in the latest release notes I read this:

The ability to stack transforms and have "attached" objects follow the rotation and translation of its parent is very useful and we use this quite a bit in our game, so I wonder if we now have to implement this ourselves or if there is an alternative approach to this now.

 

This made multiple depth sub orbit systems super handy, but now it rather more difficult/tedius to create :-(

 

Didn't really use it yet but I think you just have to add the Parent component directly. I don't know what the comment '(No transform hierarchy)' means.

 

My game depends heavy on this hierarchy. So second topic question.

 

Take a look at Unity.Transforms.Tests.
Everything you need is there, you can still have a hierarchy.

 

See Parent.cs

Code (CSharp):

1. using System;
2. using Unity.Collections;
3. using Unity.Entities;
4. using Unity.Jobs;
5.  
6. namespace Unity.Transforms
7. {
8.     [Serializable]
9.     [WriteGroup(typeof(LocalToWorld))]
10.     public struct Parent : IComponentData
11.     {
12.         public Entity Value;
13.     }
14.  
15.     [Serializable]
16.     public struct PreviousParent : ISystemStateComponentData
17.     {
18.         public Entity Value;
19.     }
20.  
21.     [Serializable]
22.     [InternalBufferCapacity(8)]
23.     [WriteGroup(typeof(ParentScaleInverse))]
24.     public struct Child : ISystemStateBufferElementData
25.     {
26.         public Entity Value;
27.     }
28. }
29.  

ISystemStateBufferElementData is new. One system can mark multiple of same component per entity. Seems very suitable for hierarchy system. (1-many)Space for 8 childs allocated by default.

Child and PreviousParent is probably a system state for the new EndFrameParentSystem. Now just setup Parent and those two will be added/managed. Should be WAY better than the old NativeMultiHashMap attach gymnastic bookkeeping that's hiding inside TransformSystem before now that we have a proper ISystemStateBufferElementData. (I had fought with so many bugs resulting from those mess)