we need a struct only sharedComponent concept

Unity Engine
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1

SharedComponents are a pain because they can contain objects, but it seems that lots of programmers would be very happy with a struct only SharedComponent :

  • Same rules as IComponentData: struct, only blittable members, no arrays.
  • Same impact on chunks as current ISharedComponentData

example :

Struct PlanetData {
public readonly ushort Id;
public readonly ushort Radius;
public readonly int3 Position;

public PlanetData(ushort id, ushort radius, int3 center)
    {
        Id = id;
        Radius = radius;
        Position = center;
    }

}
2 Likes
2

So a little more explanation to my use cases:
I make quadtree based planets, a planet is made of a set of nodes.

  • I need to process planets one by one, I m definitely not interested in other planets nodes so a sharedcomponent PlanetData would make sense for the ecs chunks.

But it’s too much of a pain with the current non-struct shared data, I often need the radius and position in my jobs so for now I just made that a IComponentData and so I’m wasting memory.

  • My nodes have a level. 0 for the biggest (less detailed) ones, 12 for the more detailed.
    It would make sense to have a Level SharedComponent ( struct with just a byte !) so all the nodes of the same level are in the same chunks, and so that I could priorise work on the highest level of detail.

But for now, I’m just using a level11 IComponentData and level12 empty IComponentData.

3

For immutable data it seems like you could use BlobAssetReference. But for dynamic shared data things are more difficult. Can you use Entity references and store data on a separate entity? Getting it by ComponentDataFromEntity<>? But some easy API for shared data would be great.

1 Like
4

You also have chunkcomponentdata, which is accessible in a job. But yes, I also feel that there might be a better way around

  • SCD
  • CCD
  • Blob
5

Sharing of data is handled by doing this:

struct MyComponent : IComponentData
{
     public Entity SharedEntityData;
}

Then using EntityManager.Get/SetComponentData or ComponentDataFromEntity in a job

1 Like
6

Would it be possible to add a simple table overview with use cases to the manual?

For each of those:

  • [Singleton] Entity with data storage (ICD / CD)
  • SCD
  • CCD
  • Blob
  • etc.

A brief summary of:

  • what is allowed (i.e. ICD, CD)
  • what is restricted (i.e. access in job, burst, etc.)
  • what is a common use case
1 Like
7

There is some value in being able to share/define data at the level of an Archetype that doesn’t seem as well suited at the Entity/Chunk level. Sorting chunks of multiple archetypes based on some archetype value is an example. For now I keep track of this Archetype/Value relationship in a hash map but only because there isn’t a well suited method of doing this in the current ECS API.