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How to Animate Multiplayer Cursors

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Re: How to Animate Multiplayer Cursors

#31

Post by tomovo »

capableweb wrote: post #29
somehnacct3757 wrote: post #20

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…

> 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…

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?

Re: How to Animate Multiplayer Cursors

#32

Post by mcphage »

agitator wrote: post #18

I was hoping that this article would go into deeper techniques than just interpolation and splines. I would be cool to see an example of how a Kalman filter approach would compare in terms of precision and latency. My expectation is that it would be the best of both worlds.

Or even a physics simulation—if the mouse is moving with a given velocity, that velocity won't change super fast. So even if your data is a bit behind, you can use physics to estimate where they probably are now. And if you get new data, and your estimation is too far off, then move the mouse to the right spot. If it's mostly correct, just base your future simulation off of the new information, so that it moves smoothly towards the correct value.

Re: How to Animate Multiplayer Cursors

#33

Post by jfim »

LeifCarrotson wrote: post #28
HWR_14 wrote: post #22

Earlier quoted context omitted.

Honestly, I don't see why you'd need to batch it ever 100ms. Sure, you don't want to send a mouse movement every time an event triggers, but surely 30fps looks smooth and won't overload the system.

You can't reliably send, fail, retry, and confirm receipt of a TCP packet in 33ms over arbitrary Internet connections. 8ms is right out. I can get 200us over a local EtherCAT realtime industrial IO network, but that's with careful management of well-isolated single-machine network conditions and it just doesn't work with a cellular modem for download and oversubscribed residential cable for upload. Assuming latency o…

The biggest problem is TCP. Ping times for multiplayer games on decent Internet connections can be on the order of 10-20ms or even lower.

Re: How to Animate Multiplayer Cursors

#36

Post by blt »

Would be interested to hear a signal processing perspective on this problem. I feel like splines might be susceptible to creating false information (e.g. ringing/overshoot), but I don't know enough about it.

Re: How to Animate Multiplayer Cursors

#37

Post by gernb »

jewel wrote: post #6

There's another approach that might work better. Instead of sampling the mouse position every 100ms, you'd save off all the mouse positions, and then send the latest batch every 100ms. The other side would then replay the exact positions, just delayed by 100ms. It'll end up with the same latency as these motion smoothing approaches, while only using slightly more bandwidth.

Am I missing how that would work? That's an exponential increase in bandwidth needed to send all the mouse positions. 1 position per 100ms per player vs 10-30 per 100 ms per player. Those positions all have to be propagated to other players. so in the first case, 10 players = 10 positions per 100ms. In the 2nd case is 100-300 positions per 100ms.

Re: How to Animate Multiplayer Cursors

#39

Post by Sohcahtoa82 »

gernb wrote: post #37
jewel wrote: post #6

There's another approach that might work better. Instead of sampling the mouse position every 100ms, you'd save off all the mouse positions, and then send the latest batch every 100ms. The other side would then replay the exact positions, just delayed by 100ms. It'll end up with the same latency as these motion smoothing approaches, while only using slightly more bandwidth.

Am I missing how that would work? That's an exponential increase in bandwidth needed to send all the mouse positions. 1 position per 100ms per player vs 10-30 per 100 ms per player. Those positions all have to be propagated to other players. so in the first case, 10 players = 10 positions per 100ms. In the 2nd case is 100-300 positions per 100ms.

Yeah but stop and think about how little bandwidth it still is.

X and Y can easily be 2 bytes each, 4 bytes total. 100 samples per second is a mere 400 bytes per second. You could do it from a dialup modem from the early 90s!

Re: How to Animate Multiplayer Cursors

#40

Post by Sohcahtoa82 »

paulryanrogers wrote: post #30

These are pointers and not cursors, unless I misunderstand. Cursor made me think of sharing tmux or IDE text sessions.

Not only is this is needless pedantry, it's also incorrect, making it a very typical HN comment.

It is not uncommon to refer to pointers as "mouse cursors" or shorten it to just "cursor". In fact, Wikipedia considers pointers to be a subset of cursors.

https://en.wikipedia.org/wiki/Cursor_(user_interface)#Pointe...

"In computer user interfaces, a cursor is an indicator used to show the current position for user interaction on a computer monitor or other display device that will respond to input from a text input or pointing device."

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