Yes. Both are “deterministic lockstep” systems. Many many games have used such a system over the years. Although it’s probably less common these days for a variety of reasons.
I think another issue with lockstep is that for it to work, each client needs all the input data from all the other clients to be able to simulate the next step, otherwise the simulations become out of sync. So how does the simulation handle both your input, and another clients input that comes in 100ms later? If you just pause until you get their input, your game is effectively pausing and running at 10 steps/second. For comparison Starcraft 1 ran at 42ms a step, or ~24 steps per second. You'd be playing in slow motion.
Games like Starcraft 1 would handle it by adding an artificial delay to your inputs (and all your opponent's inputs). Putting it into a buffer for future steps instead. If anyone remembers the latency option for "Extra high latency", this would increase the delay on inputs so that simulations did not have to pause while waiting for inputs from other clients. And then if any network fluctuations causes your input buffer of other clients to empty, you have to pause again.
In fighting games this is usually called delay-based netcode, and people hate it. It makes your inputs feel unresponsive, and in games that require fast reactions (like fighting games) gives you a smaller window to react.
Some games that used a determinism based architecture, will actually provide immediate feed back faked on the client and then some how make that work when the real stuff happens later. See Starcraft providing instant audio response when moving units or for Factorio:
https://factorio.com/blog/post/fff-83https://factorio.com/blog/post/fff-412 (second half of post)
Fighting games still typically use a deterministic simulation too. The difference is the good netcode, called rollback, works by using save states and rewinding the simulation to the time of your opponent's 100ms late input, and then resimulating the 100ms from there. You can get away with little or no delay on your own inputs.
I doubt that'll scale to games like Starcraft and Factorio, because in my example, you would need to resimulate 100ms of simulations in ~16ms. In a fighting game with 2 characters and not much else to simulate, that's a lot easier.
Recently I’ve been playing Arma Reforger with friends online on a dedicated server, and when driving vehicles the collision physics are off, especially when driving fast, making the whole scene “teleport” forward, with frames lost and the vehicle reappearing in unexpected positions.
I wonder if this is related to this type of code. The game is technically out of early access, but there’s lots to be added still on the roadmap.
Not primarily. There were weirder CPUs in the past. Today's CPUs have largely converged on floating point operations. Basically just sin/cos/tan differ now.
It's possible to write fully cross platform deterministic code today, but it's harder to do and uncommon in libraries.
Writing state synchronization and using client side prediction is generally easier. Determinism is only necessary if there are bandwidth constraints.
Not so much easier but enables a different class of cheats in games where players don't have perfect information, even with other schemes there is normally enough information leaked that similar cheats are possible. OTOH using a deterministic simulation prevents a whole class of other cheats.
What class of cheats are prevented in deterministic simulation but possible with a dedicated server running a state synchronization netcode model? I don't think any...
First, building a PERFECTLY deterministic sim is brutally difficult. Even for a single piece of hardware. It’s so so hard and expensive. A single bug “crashes” the game with a “desync” error. Making it work cross-platform was never really an issue.
Second, you’re bound by the slowest client. No one can go faster than the weakest link.
Third, you can’t stop cheating. Every client has full and complete world state. This is fine for co-op but a major issue for competitive.
Really the ONLY benefit to lockstep sync is it minimizes bandwidth. In the days or 56k this was a strict necessity. But these days client-server is almost always a better choice.
I don't know about WC1/Doom1 but WC2/Doom 2 on the Mac also supported IPX to play against PCs in addition to the native AppleTalk support they had. The only time I ever saw IPX on a Mac.
