bevy-assets

Bevy 0.19 — Assets

When to use this skill

Loading a model, texture, audio file, or scene.
Reading the loaded data back from Assets<T> once it's ready.
Reacting to load progress (AssetEvent::Added / Modified).
Spawning glTF scenes, waiting for WorldInstanceReady, reading names/extras, or owning/despawning an instance cleanly.
Enabling hot-reload during development.
Writing your own loader → see bevy-custom-assets.

Canonical pattern

use bevy::prelude::*;

fn main() { App::new() .add_plugins(DefaultPlugins.set(AssetPlugin { // Hot-reload on file change — dev-only. watch_for_changes_override: Some(true), ..default() })) .init_resource::() .add_systems(Startup, load_handles) .add_systems(Update, react_to_loads) .run(); }

#[derive(Resource, Default)] struct MyHandles { hero: Handle, bricks: Handle, }

fn load_handles(asset_server: Res, mut handles: ResMut) { // GLTF scenes are addressed by sub-asset label. handles.hero = asset_server.load("models/hero.glb#Scene0"); handles.bricks = asset_server.load("textures/bricks.png"); }

fn react_to_loads( mut ev: MessageReader<AssetEvent>, images: Res<Assets>, ) { for event in ev.read() { if let AssetEvent::LoadedWithDependencies { id } = event { if let Some(img) = images.get(*id) { info!("image loaded: {}x{}", img.width(), img.height()); } } } }


## Asset paths

```rust
use bevy::asset::AssetPath;

// `LoadContext::path()` returns `AssetPath`, not `&Path`.
// Build paths explicitly when generating handles inside a custom loader:
let path = AssetPath::from("textures/bricks.png");
let path_with_label = AssetPath::from("models/hero.glb").with_label("Scene0");
let _ = path;
let _ = path_with_label;

Asset readiness check

use bevy::prelude::*;

# fn _check(
asset_server: Res<AssetServer>,
handles: Res<MyHandles>,
# ) {
use bevy::asset::LoadState;

if asset_server.load_state(&handles.hero) == LoadState::Loaded {
    // Safe to spawn WorldAssetRoot(handles.hero.clone()).
}
# }
# #[derive(Resource)] struct MyHandles { hero: Handle<WorldAsset> }

Bevy 0.19 gotchas

LoadContext::path() returns AssetPath, not &Path. Callers that did ctx.path().to_string_lossy() need to ctx.path().path().to_string_lossy() or use the AssetPath API directly.
SeekableReader is new in 0.18. Loaders that need random access into the underlying file can ask: if let Ok(s) = reader.seekable() { /* s: &mut dyn SeekableReader */ }.
Every custom Reader implements seekable() in 0.19. Return Ok(self) when it also implements AsyncSeek; otherwise return Err(ReaderNotSeekableError). AsyncSeekForward was removed.
Advanced loads use builders in 0.19. Prefer AssetServer::load_builder() for settings, guards, untyped loads, or approval overrides; the many specialized load_* variants are deprecated.
AssetPath::resolve now takes &AssetPath. Use resolve_str/resolve_embed_str when the child path starts as text.
AssetSourceBuilder::new(...) replaces AssetSource::build().with_reader(...). Existing custom asset sources need to be re-shaped.
AssetSource channel is async_channel::Sender in 0.18 (was crossbeam_channel). Use send_blocking(...).
Image::reinterpret_size(size) returns Result in 0.18.
Sub-asset labels. path.glb#Scene0, path.glb#Mesh0/Primitive0 — distinct handles, can be loaded independently. Forgetting the label gives you the root asset, not the named one.
Hot reload is dev-only. Don't ship watch_for_changes_override: Some(true) in a release build — it polls the filesystem.
asset_server.load(...) is non-blocking. Querying Assets<T>::get immediately after returns None. Wait for AssetEvent::LoadedWithDependencies or poll load_state(...).
AssetEvent<T> is a Message, so iterate with MessageReader<AssetEvent<T>>, not the old EventReader.

About this skill

When to use this skill

Canonical pattern

Asset readiness check

Bevy 0.19 gotchas

See also