Lifetime

Persistent vs. session-based entities

When we connect to a Game World with a Game Client, the traditional approach is that all Entities originating on our Client are session-based. This means that when the Client disconnects, they will disappear from the network World for all players.

A persistent object, however, will remain on the Replication Server even when the Client or Simulator that created or last simulated it, is gone.

This allows us to create a living world where player actions leave lasting effects.

In a virtual world, examples of persistent objects are:

• A door anyone can open, close or lock

• User-generated or user-configured objects left in the world to be found by others

• Game progress objects (e.g. in PvE games)

• Voice or video messages left by users

• NPC's wandering around the world using an AI logic

• Player characters on "auto pilot" that continue affecting the world when the player is offline

• And many, many more

A persistent object with no Simulator is called an orphan. Orphans can be configured to be auto-adopted by Clients or Simulators on a FCFS basis.

At the moment, coherence supports session persistence only. This means that players can leave the World for a moment, come back, and still find persistent objects and entities. However, as soon as a World is being shut down or the Replication Server is restarted, the state is lost.