[backroll-rs] ([Discord](https://discord.gg/VuZhs9V),

[crates.io](https://crates.io/crates/backroll)) by [@james7132] and

[GGRS]([crates.io](https://crates.io/crates/ggrs)) by [@g_schup] are pure

Rust implementations of the [GGPO] rollback networking library.


_[Evo Moment 37](https://www.youtube.com/watch?v=JzS96auqau0):

Only offline or with rollback!_

Rollback networking is a peer-to-peer network technique designed to hide

network latency in fast-paced games with precise inputs. Traditional techniques

account for network transmission time by delaying the game execution, resulting

in a sluggish game-feel. Rollback uses input prediction and speculative

execution instead. Upon receiving inputs from remote clients, resimulation of

incorrect game states occurs. This allows for gameplay that "feels just

like offline". The open source standard for rollback netcode [GGPO] is used

in successful games like Skullgirls, Guilty Gear XX Accent Core +R or

Fightcade. For further explanation about rollback,

[click here](https://ki.infil.net/w02-netcode.html).

Two projects in Rust were independently created to provide a working

implementation as well as helpful resources for developers.

backroll-rs features an added abstraction for the transportation layer and

also provides a bevy plugin, [bevy-backroll]. GGRS replaces the

C-style callback API of GGPO with a simpler, more understandable control flow.

The authors of both libraries recommend backroll-rs for developement,

as it is currently more actively collaborated on.

GGRS is recommended as a learning recource and entry point,

with a plethora of internal documentation and explanation.

The main requirement to make use of both presented libraries is determinism

in your game execution. Resimulation requires that the result of progressing

the game state depending on the given inputs yield the exact same results

every time. Additionally, you need to be able to load, save and progress

your gamestate without rendering the outcome.

If you are interested in integrating rollback networking into your game or

just want to chat with other rollback developers (not limited to Rust),

check out the [GGPO Developers Discord]!

[backroll-rs]: https://github.com/HouraiTeahouse/backroll-rs

[bevy-backroll]: https://github.com/HouraiTeahouse/backroll-rs/tree/main/bevy_backroll

[GGPO Developers Discord]: https://discord.gg/8FKKhCRCCE

[GGRS]: https://github.com/gschup/ggrs

[GGPO]: https://www.ggpo.net/

[@g_schup]: https://twitter.com/g_schup

[@james7132]: https://twitter.com/james7132