Entity Prototypes

ECS has a great way to clone existing entities using EntityManager.Instantiate(entity)

Seems logical for me to construct and configure a "prototype" entity for each unit kind at game start, and then clone those prototypes as many times as needed during the game.

But, to do so, i need to make all systems to ignore this prototype entity.

I wonder if there exist any way to disable entity, or hide it form all systems?

 

"archetype" is what you are looking for.

 

nope
archetype contain only entity type definition (list of component types) but do not contain state (component values)

what i like to achieve is to get a fully configured entity, kind of "prefab" but in memory and ready to Instantiate,
with linked shared-mesh/shared-material and with defined bounds/hp/armor/etc

 

solution i see is to add a "Prototype" tag component to entity prototype,
and to make all systems to skip any entities that have it

but again not sure if it possible to make system iterate over some set of components excluding one,
would be nice to have something like:
[inject (exclude="Prototype")]

 

You can use SubtractiveComponent for that (there is an example here).

 

thank you gamevanilla
awesome, missed it

but there is another thing that blocking me from starting to implement it,
i'd like to use some builtin systems like MeshInstanceRendererSystem
i wonder how to override ComponentGroup for those systems

and also how to make default world not to auto load built in system and load extended istead

 

You could keep your prototypes in a separate World.
The system supports one world by default, but you can manually construct other ones. I'm not sure of the syntax - just saw references in the docs.

 

Yes, here is a tread on this forum, and i was able to add second world, but another world will have another entity manager

 

Not sure if I am getting what you actually want, but to make use of the current MeshInstanceRendererSystem you just add a MeshInstanRenderer and a TransformMatrix to your entity and it will use it automatically.

Also you can disable systems via

Code (CSharp):

1. World.Active.GetOrCreateManager<AnySystemName>.Enabled = false

to enable/disable systems.

 

yes I understand how to add/remove/disable systems
what i don't understand is:
1) how to extend existing system and override its ComponentGroup
2) how to make default world to use extended system instead of original (delete or disable old one that was added automatically will work, but this is not kosher way)
3) default world is created automatically, and all system that exist in the project are automatically added to it, but if i decide to create and configure my own world by hands, how to disable default world auto-generation

 

Did you find a solution to this problem appart from using a "Prototype" tag ?
I am not sure how to copy entities from one world to another...

 

@SubPixelPerfect I'm trying to fully understand what you're intention for this is. I know you'll essentially be writing more code to handle spawning, but these cases should be constrained to very few systems. Might even make sense to constrain it to only one system for each different prototype to limit it's usages.

Another way to approach this would maybe be something in line with a type that contains the Archetype alongside a collection of each of the component values that should be set.

Code (CSharp):

1. public  struct Prototype
2. {
3.     public EntityArchetype Archetype;
4.     public NativeList<IComponentData> componentValues;
5. }

Then to instantiate I'd create the following extension method:

Code (CSharp):

1. public static class EntityManagerExtensions
2. {
3.     public static Entity Instantiate(this EntityManager entityManager, Prototype prototype)
4.     {
5.         Entity entity = entityManager.CreateEntity(prototype.Archetype);
6.         for (int i = 0; i < prototype.componentValues.Lenght;  i++)
7.         {
8.             entityManager.SetComponentData(entity, prototype.componentValues[i[);
9.         }
10.         return entity;
11.     }
12. }

This way you won't be creating a bunch of entities that have to be ignored by systems, but rather creating a prototype for specific usage that can be created in a generic way. There's even room for extending this regarding shared components.

 

Well it would be nice to be able at least to create such prototypes through an editor inspector instead of manually setting all the values in the code, and then instantiate it through some EntityPrototype class, just as for Prefabs.

It would also enable faster iteration since this might enable to change default value during play instead of having to recompile your system just to change a value.
It could also enable some data compression during serialization by allowing to just pass some prototype ID instead of the full entity components if they were not changed.

At the moment in my code, I have a system specialized in instantiating entities. However, it has a huge switch on something like EntityType, and dozens of line of codes to add all required components with correct values for each. If you have dozens of different entities it can be a nightmare in my opinion

 

They have already said this is what the final version is intended to be able to do.

 

Yes, I was answering to the comment of Cyberwiz, who was asking why we would need prototypes.

 

Regarding creating it through the editor I think creating a prefab where you attach the components would work as well. Just add some hookup code to go and create the `EntityArchetype` on startup or something like that and you'll be able to pull the components everytime it gets created or something like that. While these things are nice. I do believe Unity will be delivering on their promise of being able to view these in the editor.