Visibility Management

By default, netfox synchronizes all properties to all peers, broadcasting data. This may not always be the best approach. An example is competitive games. These games often features mechanics like fog of war, invisibility, or line of sight checks. If any of these obscures a player, other players should not receive information about them, to avoid the possibility of wallhacks and other similar cheats.

This is supported by the use of visibility filters. They provide three mechanisms to determine who should receive data and who shouldn't.

Accessing the visibility filter

Both RollbackSynchronizer and StateSynchronizer supports visibility filtering. They expose a visibility_filter property that can be used to configure filtering.

Default visibility

If there's no settings configured, the visibility filter falls back to the default_visibility. By default it is true, meaning it will broadcast data to all peers.

Per-peer override

Visibility can also be set individually for each peer. This overrides the default visibility for the given peer.

An override may be true, false, or not set. An override to true means that the peer will be visible regardless of the default visibility. An override to false means that the peer will not be visible regardless of the default visibility. An unset override means it will fall back to the default_visibility.

Filter callbacks

Callbacks can also be registered, to filter peers dynamically. These filters run before the per-peer overrides. If any of the filters reject the peer, it will not receive data.

These callbacks receive the peer ID, and return a boolean:

filter.add_visibility_filter(func(peer: int):
  # Forbidden trick to halve your bandwidth :P
  return (peer % 2) == 0
)

Update modes

Visibility filters keep an internal list of visible peers. To save on compute, this list is only updated on certain configurable events. This is exposed as its update_mode property, which can take on the following values:

Never

Only update visibility when manually triggered using update_visibility()

On peer

Only update when a peer joins or leaves

Per tick loop

Update visibility before each tick loop

Per tick

Update visibility before each network tick

Per rollback tick

Update visibility after each rollback tick