asset saver example

.gitignore

@@ -1,3 +1,5 @@
 target/
 Cargo.lock
 .idea/
+
+imported_assets/

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Changelog
 
+- new example `asset_savers`
+
 ## v0.12.0 - 29.11.2024
 - Update to Bevy 0.15
 

Cargo.toml

@@ -88,3 +88,8 @@ required-features = ["csv"]
 name = "multiple_formats"
 path = "examples/multiple_formats.rs"
 required-features = ["ron", "json"]
+
+[[example]]
+name = "asset_savers"
+path = "examples/asset_savers/asset_savers.rs"
+required-features = ["ron", "json", "postcard", "bevy/file_watcher", "bevy/asset_processor"]

README.md

@@ -71,6 +71,11 @@ ron files ending on `.level.ron` and so on...
 
 See the [examples](./examples) for working Bevy apps using the different formats.
 
+## Asset savers / using the loaders in .meta files
+
+The more involved [example `asset_savers`](./examples/asset_savers) demonstrates how you can convert a json
+asset into a processed postcard asset using the `JsonAssetLoader` and `PostcardAssetSaver`.
+
 ## Compatible Bevy versions
 
 The main branch is compatible with the latest Bevy release.

examples/asset_savers/asset_savers.rs

@@ -0,0 +1,83 @@
+use bevy::asset::processor::LoadTransformAndSave;
+use bevy::asset::transformer::IdentityAssetTransformer;
+use bevy::prelude::*;
+use bevy_common_assets::json::{JsonAssetLoader, JsonAssetPlugin};
+use bevy_common_assets::postcard::{PostcardAssetPlugin, PostcardAssetSaver};
+use serde::{Deserialize, Serialize};
+
+/// This example processes a json level asset into a postcard asset (binary format)
+/// which is then loaded and rendered. If you run the example, the directory
+/// `examples/asset_savers/imported_assets` is created and populated.
+///
+/// Take a look at `examples/asset_savers/assets/trees.level.meta` to see the configuration
+/// that tells Bevy which processor to use to convert the json asset into the postcard format.
+
+fn main() {
+    App::new()
+        .add_plugins((
+            DefaultPlugins.set(AssetPlugin {
+                mode: AssetMode::Processed,
+                file_path: "examples/asset_savers/assets".to_string(),
+                processed_file_path: "examples/asset_savers/imported_assets/Default".to_string(),
+                ..default()
+            }),
+            PostcardAssetPlugin::<Level>::new(&["level"]),
+            JsonAssetPlugin::<Level>::new(&[]),
+        ))
+        .register_asset_processor::<LoadTransformAndSave<
+            JsonAssetLoader<Level>,
+            IdentityAssetTransformer<Level>,
+            PostcardAssetSaver<Level>,
+        >>(LoadTransformAndSave::new(
+            IdentityAssetTransformer::<Level>::default(),
+            PostcardAssetSaver::<Level>::default(),
+        ))
+        .init_state::<AppState>()
+        .add_systems(Startup, setup)
+        .add_systems(Update, spawn_level.run_if(in_state(AppState::Loading)))
+        .run();
+}
+
+fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
+    let level = LevelHandle(asset_server.load("trees.level"));
+    commands.insert_resource(level);
+    let tree = ImageHandle(asset_server.load("tree.png"));
+    commands.insert_resource(tree);
+    commands.spawn((Camera2d, Msaa::Off));
+}
+
+fn spawn_level(
+    mut commands: Commands,
+    level: Res<LevelHandle>,
+    tree: Res<ImageHandle>,
+    mut levels: ResMut<Assets<Level>>,
+    mut state: ResMut<NextState<AppState>>,
+) {
+    if let Some(level) = levels.remove(level.0.id()) {
+        for position in level.positions {
+            commands.spawn((
+                Sprite::from_image(tree.0.clone()),
+                Transform::from_translation(position.into()),
+            ));
+        }
+        state.set(AppState::Level);
+    }
+}
+
+#[derive(Debug, Clone, Copy, Default, Eq, PartialEq, Hash, States)]
+enum AppState {
+    #[default]
+    Loading,
+    Level,
+}
+
+#[derive(Resource)]
+struct ImageHandle(Handle<Image>);
+
+#[derive(Resource)]
+struct LevelHandle(Handle<Level>);
+
+#[derive(Deserialize, Serialize, Asset, TypePath)]
+struct Level {
+    positions: Vec<[f32; 3]>,
+}

examples/asset_savers/assets/tree.png.meta

@@ -0,0 +1,12 @@
+(
+    meta_format_version: "1.0",
+    asset: Load(
+        loader: "bevy_image::image_loader::ImageLoader",
+        settings: (
+            format: FromExtension,
+            is_srgb: true,
+            sampler: Default,
+            asset_usage: ("MAIN_WORLD | RENDER_WORLD"),
+        ),
+    ),
+)

examples/asset_savers/assets/trees.level

@@ -0,0 +1,34 @@
+{
+  "positions": [
+    [
+      42.0,
+      42.0,
+      0.0
+    ],
+    [
+      4.0,
+      32.0,
+      0.0
+    ],
+    [
+      54.0,
+      7.0,
+      0.0
+    ],
+    [
+      -61.0,
+      4.0,
+      0.0
+    ],
+    [
+      -6.0,
+      -72.0,
+      0.0
+    ],
+    [
+      6.0,
+      -89.0,
+      0.0
+    ]
+  ]
+}

examples/asset_savers/assets/trees.level.meta

@@ -0,0 +1,11 @@
+(
+    meta_format_version: "1.0",
+    asset: Process(
+        processor: "bevy_asset::processor::process::LoadTransformAndSave<bevy_common_assets::json::JsonAssetLoader<asset_savers::Level>, bevy_asset::transformer::IdentityAssetTransformer<asset_savers::Level>, bevy_common_assets::postcard::PostcardAssetSaver<asset_savers::Level>>",
+        settings: (
+            loader_settings: (),
+            transformer_settings: (),
+            saver_settings: (),
+        ),
+    ),
+)