This page is a summary of performance issues when working with Bevy.


Unoptimized debug builds

Rust without compiler optimizations is very slow. With Bevy in particular, the default debug build settings will lead to awful runtime performance. Assets are slow to load and FPS is low.

Common symptoms:

  • Loading high-res 3D models with a lot of large textures, from GLTF files, can take over 20 seconds! This can trick you into thinking that your code is not working, because you will not see anything on the screen until it is ready.
  • After spawning some 2D sprites or 3D models, framerate may drop to unplayable levels.

However, fully-optimized release builds can be slow to compile.


# in `Cargo.toml` or `.cargo/config.toml`

# Enable optimizations for dependencies (incl. Bevy), but not for our code:
opt-level = 3

# Maybe also enable only a small amount of optimization for our code:
opt-level = 1