Maps and networking work together automatically. Most of the map's content does not need to be networked because it is loaded identically on every client from the same map file.
Physics props (prop_physics) are the main exception. When the map loads, each physics prop is spawned as a fully networked object.
prop.GameObject.Network.SetOrphanedMode( NetworkOrphaned.ClearOwner );
prop.GameObject.Network.SetOwnerTransfer( OwnerTransfer.Takeover );
prop.GameObject.NetworkSpawn();
This means any client can interact with physics props - pushing, shooting, or destroying them - and the changes replicate to everyone.
Everything else in the map is loaded locally and does not go through the network system:
- World geometry and collision
- Lights and light probes
- Fog volumes
- Skyboxes
- Soundscapes
- Static props and
func_brushentities - Cubemap probes
These are all deterministic - they produce the same result on every client because they come from the same map file.
When a client joins a game, the MapInstance is part of the scene snapshot. The map loads on the client and all its entities are created locally.
The MapInstance is careful not to duplicate objects that already exist from the network. If a child GameObject was already received via the network snapshot, the map loader will skip creating it again. This prevents doubled props or conflicting state.
Maps can also contain GameObjects embedded in a scene file (world.scene). These are deserialized and added as children of the MapInstance. Any of these GameObjects that have NetworkMode.Object set will be network spawned automatically by the host.
On the client side, GameObjects that arrive via the network are not re-created from the map file - the networked version takes precedence.