Create a flexible entity system based on a graph and a persistence layer based on JSON

[aschaeffer]

The goal is to implement a flexible entity system. It is based on a bidirectional attribute graph. Entities can have typed relationships between each other.

Types

• Entity Attribute
  • Type: int
  • Key: string
  • Value: either bool, int, double or std::string
• Entity Action
  • Name
  • Implements an entity action
  • RegisterEvent
  • Publish event on action
• Entity Type
  • Name
  • Persist Flag
  • means instances of this type should be persisted
  • the type is always persisted
  • Synchronize Flag
  • means instances of this type should be synchronized with other clients
  • Typesafety
  • Entity Actions (multiple, flexible)
  • Entity Attributes (multiple, flexible)
• Entity Instance
  • Entity Type (provides the Entity Actions)
  • Entity Attributes (multiple, flexible)
  • Entity Relationships (bidirectional graph)
• Relationship Type
  • Name
  • Persist Flag
  • Synchronize Flag
  • Entity Type of the start node
  • Entity Type of the end node
• Relationship Instance
  • Relationship Type
  • Entity Attributes (muliple, flexible)
• Entity Type Renderer
  • Entity Type
  • Render Actions (before, item, after)
• Entity Instance Renderer
  • Entity Instance
  • Render Actions (before, item, after)

    Entity Base Types

• Often used functionality:
  • Emitters: Spawns entity instances (ammo, particles, ...)
  • Modifiers: Change entity attributes over iterations (ammo, particles, ...)
  • Events: Fired on Entity Action execution (picked up entity, teleport, ...)
• Base Types
  • Entity Emitter Type extends Entity Type
  • Spawns entities of a given type
  • Entity Attributes
    • ?
  • Entity Actions
    • Emit
  • Entity Emitter extends Entity Instance
  • Entity Emitter Type
  • Entity Attributes
    • Rate per second
    • Entity Type of the spawned Entity
  • Entity Modifier Type extends Entity Type
  • Modifies entities of a given type
  • Entity Attributes
    • Entity Type
  • Entity Actions
    • Modify
  • Entity Modifier extends Entity Instance
  • Entity Modifier Type
  • Entity Attributes
    • ?

      Persistence

• Load and save entities from/to JSON
• Types to load/save:
  • Entity Instances (only instances of Entity Types with the persist flag)
  • Entity Types
  • Entity Attributes
  • Relationship Types
  • Relationships
• Using uuids

  Synchronization

• Synchronize
  • Entity Types
  • Entity Instances (only instances of Entity Types with the synchronization flag)
  • Relationship Types
  • Relationships

    JavaScript Integration

• Create, read, update and delete
• Events (emitters)
• Visibility (renderers)
• Load and save JSON

  User Interface

• TODOC

  Use Cases

• Entities are used for
  • players
  • mapmodels
  • mode specific entities: flags, bases, ...
  • player state changing pickups: ammo, armor, health, ...
  • weapons and bouncers: grenades, rockets, fog grenades, ...
  • grenades
  • grenade launcher = particle emitter instance
  • grenade = particle
  • plus geometry collision particle modifier
  • decals
  • special type of particles
  • decal particle renderer
  • explosions, splinter
  • volumetric expansion of explosions (also using the densitiy attributes)
  • particle system
  • particle emitter
  • particle modifier
  • particle renderer
  • event system entities
  • positional trigger
  • positional entity

    See also

• https://github.com/inexor-game/code/wiki/Entity-System

[IAmNotHanni]

Developing this new entity is essential because the many things will be build on top of it:

• particle system
• visual scripting system
• projectile system
• mapmodel system
• pickup system
• ...

[Croydon]

I have no overview of the work on an entity system anymore. Too many issues, branches and experiments. So I'm throwing it here into the room:

Did you check out https://github.com/skypjack/entt ?