Sending entity updates to the render thread

[eranimo]

Background

• passing data between the two threads:
  • game thread: game.worker.ts - handles simulation, game loop
  • render thread: (i.e. main thread) GameManager.ts - renders React UI, map renderer
• data is sent to the render thread using:
  • "shared memory" - SharedArrayBuffers (population map mode uses this)
    • this is hugely performant for very fast updates and anything that can be expressed in 2D
  • "data passing" - observables, passed via postMessage-style events I called "channels". Render thread only receives updates to observables they subscribe to, not all of them. Components that listen to these should unsubscribe from the channel after they unmount.
    • this is less memory efficient but it's far easier to use
• ObservableDict allows you to observe both a specific key or the entire dict itself.

Problem

• This above is kinda clunky and primitive, since what we really want is an "entity system" that can:
  • have references to each other (game cell -> pop for instance)
  • easily send updates to the render thread
  • work with the game loop
  • use as little memory as possible

Proposal

• Entities have an ID and a type.
• Entities have an ObservableDict called data whose values can be anything JSON serializable, or special types which we define, one of which is a Reference object to another Entity (more will probably be added later)

Open questions

• Should entities have references, or should a "manager" class hold the references?
• Is the above proposal too memory inefficient?
• should attributes be defined as observables that belong to an entity, which is simply an ID number in a lookup table? (this is called an entity-attribute system). This might be more flexible, and better allow for references.
• How should the entity updates be sent?

Related

• https://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model