Bevy Scene hook

A one-file proof of concept for adding components ad-hoc within code to entities spawned through scenes (such as gltf files) in the bevy game engine.

If you don't mind adding such a small dependency to your code rather than copy/pasting the code as a module, you can get it from crates.io.

Usage

[dependencies]
bevy-scene-hook = "1.2"

The following snippet of code is extracted from Warlock's Gambit source code.

It loads the scene.glb file when the game state becomes GameState::Loading. It then runs the Scene::hook method once using the Scene::when_not_spawned run criteria, Scene::hook runs the Scene::hook_named_node method for each named entity in the scene and adds specific components to them. Most notably the animation ones. It then leaves the GameState::Loading state using the Scene::when_spawned run criteria.

It is possible to name object in glb scenes in blender using the Outliner dock (the tree view at the top right) and double-clicking object names.

use bevy::{
    ecs::system::EntityCommands,
    prelude::{Plugin as BevyPlugin, *},
};
use bevy_scene_hook::{SceneHook, SceneInstance};
use crate::{
    animate::Animated,
    camera::PlayerCam,
    common_components::{OppoCardSpawner, OppoHand, PlayerCardSpawner, PlayerHand, PlayerSleeve},
    pile::{Pile, PileType},
    state::GameState,
};
pub enum Scene {}
impl SceneHook for Scene {
    fn hook_named_node(name: &Name, cmds: &mut EntityCommands) {
        match name.as_str() {
            "PlayerPerspective_Orientation" => cmds.insert(PlayerCam),
            "PlayerCardSpawn" => cmds.insert(PlayerCardSpawner),
            "OppoCardSpawn" => cmds.insert(OppoCardSpawner),
            "OppoHand" => cmds.insert_bundle((OppoHand, Animated::bob(1.0, 0.3, 6.0))),
            "PlayerHand" => cmds.insert_bundle((PlayerHand, Animated::bob(2.0, 0.05, 7.0))),
            "Pile" => cmds.insert(Pile::new(PileType::War)),
            "OppoPile" => cmds.insert(Pile::new(PileType::Oppo)),
            "PlayerPile" => cmds.insert(Pile::new(PileType::Player)),
            "ManBody" => cmds.insert(Animated::breath(0.0, 0.03, 6.0)),
            "ManHead" => cmds.insert(Animated::bob(6. / 4., 0.1, 6.0)),
            "Bird" => cmds.insert(Animated::breath(0.0, 0.075, 5.0)),
            "BirdEyePupilla" => cmds.insert(Animated::bob(5. / 4., 0.02, 5.0)),
            "PlayerSleeveStash" => cmds.insert(PlayerSleeve),
            _ => cmds,
        };
    }
}
fn setup_scene(
    mut cmds: Commands,
    mut scene_spawner: ResMut<SceneSpawner>,
    asset_server: Res<AssetServer>,
) {
    let gltf = scene_spawner.spawn(asset_server.load("scene.glb#Scene0"));
    cmds.spawn().insert(SceneInstance::<Scene>::new(gltf));
}
fn exit_load_state(mut state: ResMut<State<GameState>>) {
    if state.current() == &GameState::LoadScene {
        state.set(GameState::Playing).unwrap();
    }
}
pub struct Plugin;
impl BevyPlugin for Plugin {
    fn build(&self, app: &mut App) {
        app.add_system_set(SystemSet::on_enter(GameState::Loading).with_system(setup_scene))
            .add_system(exit_load_state.with_run_criteria(Scene::when_spawned))
            .add_system(Scene::hook.with_run_criteria(Scene::when_not_spawned));
    }
}

If SceneHook is too weak for you and you need access to queries or world resources (mutable or not), you can use world::SceneHook instead.

Limitations

• You will need to keep track of what you name what.
• The bevy gltf loader currently doesn't name entities associated with a mesh (the entity with the Handle<Mesh> component), this is fixed in a pending PR.

Change log

• 1.1.0: Add is_loaded method to SceneInstance
• 1.2.0: Add the world module containing a SceneHook trait that has exclusive world access. Useful if you want access to assets for example.

License

This library is licensed under Apache 2.0.