fixed-step-simulation

To make Unity DOTS physics deterministic for network prediction, run your systems in FixedStepSimulationSystemGroup and use SystemAPI.Time.DeltaTime to ensure the simulation consumes a fixed delta rather than the variable render delta.

Variable DeltaTime causes inconsistent Unity gameplay results because fluctuating render frame times lead to incorrect physics integration and gameplay that changes depending on performance. Decoupling the simulation tick rate resolves this.

To run a Unity system at a fixed timestep, add the UpdateInGroup attribute targeting FixedStepSimulationSystemGroup. This ensures your logic updates at a known rate like 60Hz regardless of the render framerate.

You need a fixed timestep decoupled from render framerate for physics-driven gameplay, deterministic replay, and network prediction where variable DeltaTime would produce incorrect simulation results.

Yes, you can use FixedStepSimulationSystemGroup with Unity DOTS. It enables fixed-timestep ticking for selected systems while maintaining explicit state handoffs to your render-rate systems for deterministic execution.