Class PredictedSimulationSystemGroup
The parent group for all "deterministic" gameplay systems that modify predicted ghosts. This system group runs for both the client and server worlds at a fixed time step, as specified by the SimulationTickRate setting.
On the server, this group is only updated once per tick, because it runs in tandem with the SimulationSystemGroup (i.e. at a fixed time step, at the same rate). On the client, the group implements the client-side prediction logic by running the client simulation ahead of the server.
Importantly: Because the client is predicting ahead of the server, all systems in this group will be updated multiple times per simulation frame, every single time the client receives a new snapshot (see NetworkTickRate and SimulationTickRate). This is called "rollback and re-simulation".
These re-simulation prediction group ticks also get more frequent at higher pings. I.e. Simplified: A 200ms client will likely re-simulate roughly x2 more frames than a 100ms connection, with caveats. And note: The number of predicted, re-simulated frames can easily reach double digits. Thus, systems in this group must be exceptionally fast, and are likely your CPU "hot path". To help mitigate this, take a look at prediction group batching here MaxPredictionStepBatchSizeRepeatedTick.
Pragmatically: This group contains most of the game simulation (or, at least, all simulation that should be "predicted" (i.e. simulation that is the same on both client and server)). On the server, all prediction logic is treated as authoritative game state (although thankfully it only needs to be simulated once, as it's authoritative).
Note: This SystemGroup is intentionally added to non-netcode worlds, to help enable single-player testing.
Inheritance
Inherited Members
Namespace: Unity.NetCode
Assembly: Unity.NetCode.dll
Syntax
[WorldSystemFilter(WorldSystemFilterFlags.Default|WorldSystemFilterFlags.ThinClientSimulation, WorldSystemFilterFlags.Default)]
[UpdateInGroup(typeof(SimulationSystemGroup), OrderFirst = true)]
[UpdateBefore(typeof(FixedStepSimulationSystemGroup))]
[UpdateAfter(typeof(BeginSimulationEntityCommandBufferSystem))]
public class PredictedSimulationSystemGroup : ComponentSystemGroupRemarks
To reiterate: Because child systems in this group are updated so frequently (multiple times per frame on the client, and for all predicted ghosts on the server), this group is usually the most expensive on both builds. Pay particular attention to the systems that run in this group to keep your performance in check.