https://github.com/johanhelsing/bevy_roll_safe

Rollback-safe implementations and utilities for Bevy Engine
https://github.com/johanhelsing/bevy_roll_safe

bevy deterministic game-development rollback

Last synced: 10 months ago
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Rollback-safe implementations and utilities for Bevy Engine

• Host: GitHub
• URL: https://github.com/johanhelsing/bevy_roll_safe
• Owner: johanhelsing
• License: apache-2.0
• Created: 2023-09-11T06:21:24.000Z (over 2 years ago)
• Default Branch: main
• Last Pushed: 2024-12-19T21:06:34.000Z (about 1 year ago)
• Last Synced: 2025-03-28T16:37:58.832Z (11 months ago)
• Topics: bevy, deterministic, game-development, rollback
• Language: Rust
• Homepage:
• Size: 43 KB
• Stars: 14
• Watchers: 2
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-APACHE

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README

          
# bevy_roll_safe

[![crates.io](https://img.shields.io/crates/v/bevy_roll_safe.svg)](https://crates.io/crates/bevy_roll_safe)

![MIT/Apache 2.0](https://img.shields.io/badge/license-MIT%2FApache-blue.svg)

[![docs.rs](https://img.shields.io/docsrs/bevy_roll_safe)](https://docs.rs/bevy_roll_safe)

Rollback-safe implementations and utilities for Bevy Engine.

## Motivation

Some of Bevy's features can't be used in a rollback context (with crates such as [`bevy_ggrs`]). This is either because they behave non-deterministically, rely on inaccessible local system state, or are tightly coupled to the `Main` schedule.

## Roadmap

- [x] States

  - [x] Basic freely mutable states

  - [x] `OnEnter`/`OnLeave`/`OnTransition`

  - [ ] Sub-States

  - [ ] Computed states

  - [ ] Roll-safe events

- [x] FrameCount

- [ ] Events

## States

Bevy states when added through `app.add_state::()` have two big problems:

1. They happen in the `StateTransition` schedule within the `MainSchedule`

2. If rolled back to the first frame, `OnEnter(InitialState)` is not re-run.

This crate provides an extension method, `add_roll_state::(schedule)`, which lets you add a state to the schedule you want, and a resource, `InitialStateEntered` which can be rolled back and tracks whether the initial `OnEnter` should be run (or re-run on rollbacks to the initial frame).

See the [`states`](https://github.com/johanhelsing/bevy_roll_safe/blob/main/examples/states.rs) example for usage with [`bevy_ggrs`].

## Cargo features

- `bevy_ggrs`: Enable integration with [`bevy_ggrs`]

- `math_determinism`: Enable cross-platform determinism for operations on Bevy's (`glam`) math types.

## Bevy Version Support

|bevy|bevy_roll_safe|

|----|--------------|

|0.15|0.4, main     |

|0.14|0.3           |

|0.13|0.2           |

|0.12|0.1           |

## License

`bevy_roll_safe` is dual-licensed under either

- MIT License (./LICENSE-MIT or )

- Apache License, Version 2.0 (./LICENSE-APACHE or )

at your option.

## Contributions

PRs welcome!

[`bevy_ggrs`]: https://github.com/gschup/bevy_ggrs