> The server simulates the game in discrete time steps called ticks. By default, the timestep is 15ms, so 66.666... ticks per second are simulated, but mods can specify their own tickrate. During each tick, the server processes incoming user commands, runs a physical simulation step, checks the game rules, and updates all object states.
Havok made the legacy engine used in Source 1 free of license fees in 2021. Before that it was $25,000 per title. Source 2 uses in-house Rubikon to dodge those fees: https://developer.valvesoftware.com/wiki/Havok
> The server, as central authority, processes player input and updates the world according to the game and physics rules.
https://developer.valvesoftware.com/wiki/Source_Multiplayer_...
> The server simulates the game in discrete time steps called ticks. By default, the timestep is 15ms, so 66.666... ticks per second are simulated, but mods can specify their own tickrate. During each tick, the server processes incoming user commands, runs a physical simulation step, checks the game rules, and updates all object states.
Havok made the legacy engine used in Source 1 free of license fees in 2021. Before that it was $25,000 per title. Source 2 uses in-house Rubikon to dodge those fees: https://developer.valvesoftware.com/wiki/Havok