Firefly

Firefly is an open-source, 2d lighting crate for the bevy game engine.

I am working on it as part of my college thesis. It uses certain geometrical and computational algorithms to take advantage of Bevy's ECS and put less strain on the GPU.

My final goal is to have a lighting crate with features akin to the ones of more mature game engines, while keeping performance as high as possible and minimizing the end-user API.

Firefly is still pretty early in development, with many features to be added still. However, there is already lot of cool stuff for you to play with or use for your games, if you wish to.

Short video showing off soft shadows and z-sorting:

2025-11-19_03-44-04.mp4

Credit for the characters and assets to Kimberly and her upcoming game!

Here's the same game but with light banding and hard shadows:

Screencast.From.2025-11-24.00-50-49.mp4

Here's a video of the crates example, showcasing normal maps and z-sorting:

crates_example.mp4

Credit for the characters and assets to Kimberly and her upcoming game!

And here is a video of the shapes example.

Screencast.From.2025-11-24.01-36-46.mp4

Usage

To use this crate, simply run cargo add bevy_firefly or add firefly to your Cargo.toml file.

You can see all the firely versions here.

Here is a basic example of integrating firefly into a bevy app:

use bevy::prelude::*;
use bevy_firefly::prelude::*;

fn main() {
  App:new()
    .add_plugins((DefaultPlugins, FireflyPlugin))
    .add_systems(Startup, setup)
    .run();
}

fn setup(mut commands: Commands) {
  commands.spawn((
    Camera2d,
    FireflyConfig::default()
  ));
     
  commands.spawn((
    PointLight2d {
      color: Color::srgb(1.0, 0.0, 0.0),
      range: 100.0,
      ..default()
    },
    Transform::default()
  ));
     
  commands.spawn((
    Occluder2d::circle(10.0),
    Transform::from_translation(vec3(0.0, 50.0, 0.0)),
  ));
}

Check out the examples and the crate documentation to learn more about using it.

Features

Some of the existing features are:

• Dynamic lights and occluders
• Point lights
• Round and polygonal occluders
• Soft shadows
• Occlusion z-sorting
• Normal maps
• Occlusion sprite masking
• Transparent & colored occluders
• Light banding

Some of the currently planned features are:

• Occluders casting sprite-based shadows
• Mulitple lightmaps
• Light textures

Feel free to open an issue if you want to request any specific features or report any bugs!

Also you can ask any questions over on discord!

Bevy Compatibility

bevy	bevy_firefly
0.16	0.16
0.17	0.17

Alternatives

You can check out bevy_light_2d and bevy_lit. They were both a big inspiration when starting out with this crate!