Module crayon::ecs

The entity component system with a data-orinted designs.

Entity Component System (ECS)

ECS is an architectural pattern that is widely used in game development. It follows the Composition over Inheritance principle that allows greater flexibility in defining entities where every object in a game's scene in an entity.

Entity

Entity is one of the most fundamental terms in this system. Its basicly some kind of unique identifier to the in-game object. Every Entity consists of one or more Components, which define the internal data and how it interacts with the world.

Its also common that abstracts Entity as container of components, buts with UID approach, we could save the state externaly, users could transfer Entity easily without considering the data-ownerships. The real data storage can be shuffled around in memory as needed.

Component

TODO

Data Orinted Design

Data-oriented design is a program optimization approach motivated by cache coherency. The approach is to focus on the data layout, separating and sorting fields according to when they are needed, and to think about transformations of data.

Due to the composition nature of ECS, its highly compatible with DOD. But benefits doesn't comes for free, there are some memory/performance tradeoff generally. We addressed some data storage approaches in ecs::component, users could make their own decision based on different purposes:

struct Position(f32, f32, f32);
struct Label(String);

// Vec based storage, supposed to have maximum performance for the components
// mostly present in entities.
impl Component for Position {
    type Storage = VecArena<Position>;
}

// HashMap based storage which are best suited for rare components.
impl Component for Label {
    type Storage = HashMapArena<Label>;
}

System and Dispatcher

TODO

Reexports

pub use self::component::Component;

pub use self::component::ComponentArena;

pub use self::component::HashMapArena;

pub use self::component::VecArena;

pub use self::world::Arena;

pub use self::world::ArenaMut;

pub use self::world::Fetch;

pub use self::world::FetchMut;

pub use self::world::View;

pub use self::world::World;

pub use self::system::System;

Modules

bitset	Bit-set with fixed or dynamic size for Ecs.
cell	A thread-safe RefCell.
component	Abstract Component trait and some common storage stratedy.
system	Execution utilities based on View and Arenas.
world	The World struct contains entities and its the component arenas.

Type Definitions

Entity

Entity type, as seen by the user, its a alias to Handle internally.