bevy/examples/asset/hot_asset_reloading.rs

use bevy::prelude::*;

/// Hot reloading allows you to modify assets on disk and they will be "live reloaded" while your
/// game is running. This lets you immediately see the results of your changes without restarting
/// the game. This example illustrates hot reloading mesh changes.
fn main() {
    App::build()
        .add_plugins(DefaultPlugins)
        .add_startup_system(setup.system())
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    // Load our mesh:
    let scene_handle = asset_server.load("models/monkey/Monkey.gltf#Scene0");

    // Tell the asset server to watch for asset changes on disk:
    asset_server.watch_for_changes().unwrap();

    // Any changes to the mesh will be reloaded automatically! Try making a change to Monkey.gltf.
    // You should see the changes immediately show up in your app.

    // mesh
    commands.spawn_scene(scene_handle);
    // light
    commands.spawn_bundle(PointLightBundle {
        transform: Transform::from_xyz(4.0, 5.0, 4.0),
        ..Default::default()
    });
    // camera
    commands.spawn_bundle(PerspectiveCameraBundle {
        transform: Transform::from_xyz(2.0, 2.0, 6.0).looking_at(Vec3::ZERO, Vec3::Y),
        ..Default::default()
    });
}