Nebula

Entity Component System

Quick Start

Entity, Component, System are all instantiated and managed through a World object.

All user-defined Components and Systems must contain the following static member:

static constexpr uint32_t ID = GENERATE_ID( "ExampleClassName" );

The ID allows the ECS to generate a unique identifier for the given component or system at compile-time.

This ID must be passed as a paramter to the parent constructor call in classes derived from System and Component, see example below:

class FooComponent : public Nebula::Component {
public:
	static constexpr uint32_t ID = GENERATE_ID( "FooComponent" );

	FooComponent(): 
        Component(ID) 
    {};

	~FooComponent() = default;
};

Once instantiated, the Nebula::World object is responsible for creating entities and adding/removing components from entities at run-time.

All systems should be registered before their components are added to entities.

Nebula::Parser<...> can be used on a World object to obtain all entities with the matching Component signature, see example below:

Nebula::Parser<AudioComponent, PhysicsComponent>( WorldObject );

Systems

All Systems are defined by its Component Signature, the components that need to be present on the Entity to be updated within this System, see example below:

class FooSystem : public Nebula::System<FooComponent, FoobarComponent>
{
public:
	static constexpr uint64_t ID = GENERATE_ID("FooSystem");

	FooSystem(): 
        System(ID) 
    {}
	~FooSystem() = default;
};

All user-defined systems must be registered with a World object at run-time.

std::get<FooComponent*> can be used to obtain elements of component signatures (std::tuple)

Features

Custom constructors are supported for user-defined Component and System classes.