docs: Inputless RollbackSynchronizers (#528)

Closes #450

Author: elementbound

docs/netfox/tutorials/using-rollbacksynchronizer-without-inputs.md

@@ -0,0 +1,26 @@
+# Using RollbackSynchronizer without inputs
+
+In certain cases, a component needs to participate in rollback, but is not
+driven by any input. One example could be more complex NPCs. These need to be
+part of the rollback tick loop, but they are not controlled by any player.
+
+In these cases, you can use RollbackSynchronizer as described earlier in
+[Responsive player movement], but without the input. This means not needing an
+input node, and not configuring any input properties. State properties still
+need to be configured, and the gameplay logic must be implemented in
+`_rollback_tick()`.
+
+!!!tip
+    An example project featuring a simple NPC using an inputless
+    RollbackSynchronizer can be found at [examples/rollback-npc].
+
+Under the hood, *netfox* will simulate these inputless nodes whenever it
+encounters a tick that has no state for the inputless node. On the server, this
+means inputless nodes will be simulated only for new ticks. On clients, this
+means never being simulated, since all state is received from the server. If
+prediction is enabled, clients will simulate inputless nodes for ticks they
+don't have data from the server.
+
+
+[Responsive player movement]: ./responsive-player-movement.md
+[examples/rollback-npc]: https://github.com/foxssake/netfox/tree/main/examples/rollback-npc

mkdocs.yml

@@ -36,6 +36,7 @@ nav:
       - 'netfox/tutorials/responsive-player-movement.md'
       - 'netfox/tutorials/input-gathering-tips-and-tricks.md'
       - 'netfox/tutorials/predicting-input.md'
+      - 'netfox/tutorials/using-rollbacksynchronizer-without-inputs.md'
       - 'netfox/tutorials/modifying-objects-during-rollback.md'
       - 'netfox/tutorials/configuring-properties-from-code.md'
       - 'netfox/tutorials/rollback-caveats.md'