> Bevy uses the ECS pattern to organize game code, and it occurred to me that ECS substantially alleviates the spaghetti-code problem that makes testing in Unity and Unreal so terrible.
Both Unreal and Unity uses ECS.
Both Unreal and Unity uses ECS.
Entity-Compontity-System (ECS) uses these nouns differently; an Entity ends up being little more than an identifier for a large number of Components, which are data structures, and Systems are the code that modify groups of Components. "System" here is a noun, not a descriptor of the practice. The usual analogy is similar to a relational database (in fact, the point of the system is to achieve wide-scale performance like RDSes do): Entities are rows, identified by a primary key, Components are columns, and Systems are the SELECT/INSERT/UPDATE/DELETE queries which acts on the data.
Unity has a new-ish ECS framework under the DOTS initiative; Unreal has no parallel. Very few games are using these.
It uses different terminology such as fragments. Traits and others but its incredibly powerful and scalable.
This is a separate system then the ec of actors and components.
ECS has come to mean a very particular style of architecture. It's not a great name, but it's what the industry has converged on. Naming things is hard.
Unity's MonoBehavior framework uses GameObjects and Components. You don't have to squint hard to see that it contains Entities, Components, and arguably Systems. However ECS has come to mean an architecture that is quite different from MonoBehavior. So different infact that Unity is writing an ECS framework called DOTS!
Both DOTS and MonoBehaviors containing entities, components, and functions that operate on them. However the two Unity systems are extremely different. MonoBehaviors are not an ECS.
Then some people started talking about a single implementation style of ECS as if that was all ECS is, Unity DOTS is an example of that, but the base Unity is still ECS at its core.
Unreal's framework is a mix of inheritance and components. It's clunky AF. AActor I'm looking at you!
Neither Unreal nor Unity provide a mechanism to cleanly query such as "give me all gameobjects in the world contain this set of components". And they definitely don't provide a mechanism to perform that query quickly.
Unity will let you search from components within a GameObject, in children, or in scene. These queries are also slow as fuck and should generally be avoided.
The type of code you write in Unity and in a Bevy-style ECS is quite different. I think ECS is overrated in some ways as it's actually pretty difficult and non-obvious how to accomplish a lot of tasks.
I don't love the name ECS. It's just not a great name. However I've come to terms with it. ECS has colloquially come to mean something that is extremely distinct from MonoBehaviors. You're welcome to keep fighting the community accepted definition if you want. I don't think it's useful or helpful to do so.
But yes, everyone admits the names are confusing. But at no point does Unity or Unreal say their architecture is an ECS one.
"Component Systems" were popularized ~20 years ago. I'd consider Unity MonoBehaviors a typical Component implementation. Scott Bilas's 2002 GDC presentation "A Data-Driven Game Object System" helped evangelize the idea.
ECS is a new term that implies a handful of implementation details. The name is somewhat confusing, but it's not redefining a previously popular term.
I believe the first time ECS made an appearance at GDC was Blizzard's stellar 2017 talk "Overwatch Gameplay Architecture and Netcode". The term went mainstream in the years after this.
EC was the answer to God objects and deep, inflexible inheritance hierarchies.
Among other things, ECS is partially a performance play - it's more cache friendly. I'm not sure what all the tradeoffs are though, I've only really used EC.
A proper system, for example, would be able to add a new enemy entity every 5 seconds and switch the flag that the level is cleared once the total count of present enemies is 0. In fact, it would be quite trivial to implement it. But in Unity you would need some sort of an architectural solution to bypass inherent limitations of EC-S.
There are a few ECS approach and to this day it's still vague who does it best (depends on your goals).
One I found interesting is the "sparse entity component system".
My guess is what he meant was that the Bevy approach is cleaner to test upon.
https://docs.unrealengine.com/5.0/en-US/overview-of-mass-ent...
I realize that there's the whole "grouping" and "batching" concept in ECS paradigms, but I'm failing to see how that's much different from using the functions in `UWorld` that can query both components and actors of a certain class.