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Comment by somehnacct3757 | Hacker News Reader

This is analogous to player position in any multiplayer game.

One additional parameter to keep in mind is how real-time does your simulation of remote players need to be? If you don't need real-time positioning there's a whole other dimension of shortcuts you can take by introducing what amounts to a 'streaming delay'.

In a lot of these apps the cursors can't interact with each other so you have no need for real-time positioning and its accompanying smoothing techniques. Cheat cheat cheat! That's how games get their performance, way more often than being smart they're clever opportunistic cheaters!

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> This is analogous to player position in any multiplayer game.

Not sure. Multiplayer games are easier to predict player movement. Once someone starts moving forward, you can predict that they'll move forward for a little while, start turning, continue forward and so on. Add in physics (like the motions/movements of a car, or the running of a human) and there will be constraints the player can't break (when you stop moving forward, you'll move forward slower and slower until you stop, maybe over 100ms or so)

But mouse movement is highly erratic. It'll be short of impossible to add any sort of prediction, as it'll be incorrect most of the time, instead of being mostly correct but sometimes not.

The real fun starts when online players start shooting at each other. How to decide if a hit was fair AND make it look believable for both parties to minimize outrage?

> AND make it look believable for both parties to minimize outrage?

Call of Duty MW2 used to replay what your opponent saw, after your death. That always made an inexplicable death much easier to swallow.

Of course, they probably had to add that feature since they did away with dedicated servers, but it was still nice.

It's very common for games to deal with erratic input from keyboard controls. Consider player position in a moba or fps where two humans are responding to each others' presence (footsie.)

The penalty for a wrong prediction is rubber banding, so if you can get away with streaming their past at high latency, I would avoid predicting at all.

That's the model often used by async PvE games (think social games, invest/express, etc) and I think that approach would map best onto SaaS presence features.

Have you ever played a multiplayer game? Have you seen how people move in FPS games? Highly erratic, especially during gun fights. Instantaneous starting and stopping.

Your example is only relevant if the player just loves to hold down the "move forward" key for long periods of time.

Here's a series of articles about client-server game architecture which I found tremendously interesting, and it's a bit more involved than what's explained in this article on cursor positions though I agree the basics are similar. It starts out explaining a naive approach, identifying the issues with that, and moving to more advanced solutions which involve prediction. The article also has a good explanation that goes a bit more in-depth to how the latency causes issues with the gameplay.

https://www.gabrielgambetta.com/client-server-game-architect...

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