bevy_world_serialization

The format layer for scenes and prefabs. Defines BSN (Bevy Scene Notation), reflection-driven RON serialization, and the type registry plumbing scenes need.

Purpose

Carved out of bevy_scene so the format itself can evolve independently of the runtime spawning logic. This crate provides:

• BSN — Bevy's bespoke human-readable scene format.
• Reflection-driven RON for round-tripping Worlds.
• Asset support for .bsn files.
• Scene merging semantics (DynamicScene-style).

Directory layout

crates/bevy_world_serialization/src/
├── lib.rs
├── bsn/                # BSN parser + AST
├── world_serialize.rs  # Serialize a World to RON via reflection
├── world_deserialize.rs
└── …

Key abstractions

Type	File	Description
BsnAsset	crates/bevy_world_serialization/src/bsn/	Parsed BSN file.
Scene (re-exposed)	crates/bevy_world_serialization/src/lib.rs	A World snapshot ready for spawning.
Loader for .bsn / .scn.ron	crates/bevy_world_serialization/src/lib.rs	Asset loaders.

How it works

BSN

BSN is a structured scene format inspired by RON but specialized for component composition. It supports nested entities, component tuples, asset references, and reflectable expressions for component values. The parser is in bsn/.

Reflection-driven RON

Existing .scn.ron scenes use bevy_reflect's serde codec to encode each component's reflected value. The implementation walks every entity in the source World and produces a stable RON representation. Loading is the inverse: parse RON → look up types by name in the TypeRegistry → reconstruct components → spawn entities.

Integration points

• Depends on: bevy_app, bevy_ecs, bevy_asset, bevy_reflect, serde, ron.
• Depended on by: bevy_scene (the runtime side), bevy_gltf (which produces a scene from glTF), bevy_remote (the BRP serializes via the same reflection path).

Entry points for modification

• BSN syntax changes: bsn/parse.rs plus the AST modules.
• RON format tweaks: world_serialize.rs / world_deserialize.rs. The format is reflection-driven so additions to types automatically flow through.
• Custom asset reference syntax: bsn/.

See also

• bevy_scene — the consumer that spawns scenes.
• bevy_reflect — drives the codec.
• Scenes feature page.