The heartbeat of the world
A game server advances the world in discrete steps called ticks. The tick rate is how many ticks run per second, often twenty to sixty four. Each tick the server gathers inputs, advances physics by a fixed timestep, and may send updates.
Why fixed steps matter
- A fixed timestep keeps physics deterministic, so the same inputs always yield the same result.
- Determinism is what makes prediction, reconciliation, and replays possible.
- Variable steps would make collisions and movement drift between machines.
The tradeoffs
- A higher tick rate means crisper hit detection and lower input delay but more CPU and bandwidth.
- A lower tick rate saves resources but adds quantization error, the world only updates so often.
- Send rate can be decoupled from tick rate, simulating fast while transmitting less often.
A common pattern simulates at a fixed rate while interpolating rendered frames on the client so visuals stay smooth between ticks.
Key idea
A fixed tick advances the world deterministically, and its rate trades responsiveness against CPU and bandwidth.