Hot asset reloading

Cargo.toml

@@ -111,6 +111,14 @@ path = "examples/app/headless.rs"
 name = "plugin"
 path = "examples/app/plugin.rs"
 
+[[example]]
+name = "hot_asset_reload"
+path = "examples/asset/hot_asset_reload.rs"
+
+[[example]]
+name = "asset_loading"
+path = "examples/asset/asset_loading.rs"
+
 [[example]]
 name = "custom_diagnostic"
 path = "examples/diagnostics/custom_diagnostic.rs"

assets/models/cube/cube.gltf

@@ -0,0 +1,122 @@
+{
+    "asset" : {
+        "generator" : "Khronos glTF Blender I/O v1.1.46",
+        "version" : "2.0"
+    },
+    "scene" : 0,
+    "scenes" : [
+        {
+            "name" : "Scene",
+            "nodes" : [
+                0
+            ]
+        }
+    ],
+    "nodes" : [
+        {
+            "mesh" : 0,
+            "name" : "Cube"
+        }
+    ],
+    "materials" : [
+        {
+            "doubleSided" : true,
+            "emissiveFactor" : [
+                0,
+                0,
+                0
+            ],
+            "name" : "Material",
+            "pbrMetallicRoughness" : {
+                "baseColorFactor" : [
+                    0.800000011920929,
+                    0.800000011920929,
+                    0.800000011920929,
+                    1
+                ],
+                "metallicFactor" : 0,
+                "roughnessFactor" : 0.4000000059604645
+            }
+        }
+    ],
+    "meshes" : [
+        {
+            "name" : "Cube",
+            "primitives" : [
+                {
+                    "attributes" : {
+                        "POSITION" : 0,
+                        "NORMAL" : 1,
+                        "TEXCOORD_0" : 2
+                    },
+                    "indices" : 3,
+                    "material" : 0
+                }
+            ]
+        }
+    ],
+    "accessors" : [
+        {
+            "bufferView" : 0,
+            "componentType" : 5126,
+            "count" : 24,
+            "max" : [
+                1,
+                1,
+                1
+            ],
+            "min" : [
+                -1,
+                -1,
+                -1
+            ],
+            "type" : "VEC3"
+        },
+        {
+            "bufferView" : 1,
+            "componentType" : 5126,
+            "count" : 24,
+            "type" : "VEC3"
+        },
+        {
+            "bufferView" : 2,
+            "componentType" : 5126,
+            "count" : 24,
+            "type" : "VEC2"
+        },
+        {
+            "bufferView" : 3,
+            "componentType" : 5123,
+            "count" : 36,
+            "type" : "SCALAR"
+        }
+    ],
+    "bufferViews" : [
+        {
+            "buffer" : 0,
+            "byteLength" : 288,
+            "byteOffset" : 0
+        },
+        {
+            "buffer" : 0,
+            "byteLength" : 288,
+            "byteOffset" : 288
+        },
+        {
+            "buffer" : 0,
+            "byteLength" : 192,
+            "byteOffset" : 576
+        },
+        {
+            "buffer" : 0,
+            "byteLength" : 72,
+            "byteOffset" : 768
+        }
+    ],
+    "buffers" : [
+        {
+            "byteLength" : 840,
+            "uri" : "cube.bin"
+        }
+    ]
+}

assets/models/sphere/sphere.gltf

@@ -0,0 +1,100 @@
+{
+    "asset" : {
+        "generator" : "Khronos glTF Blender I/O v1.1.46",
+        "version" : "2.0"
+    },
+    "scene" : 0,
+    "scenes" : [
+        {
+            "name" : "Scene",
+            "nodes" : [
+                0
+            ]
+        }
+    ],
+    "nodes" : [
+        {
+            "mesh" : 0,
+            "name" : "Sphere"
+        }
+    ],
+    "meshes" : [
+        {
+            "name" : "Sphere",
+            "primitives" : [
+                {
+                    "attributes" : {
+                        "POSITION" : 0,
+                        "NORMAL" : 1,
+                        "TEXCOORD_0" : 2
+                    },
+                    "indices" : 3
+                }
+            ]
+        }
+    ],
+    "accessors" : [
+        {
+            "bufferView" : 0,
+            "componentType" : 5126,
+            "count" : 2143,
+            "max" : [
+                1.0000005960464478,
+                1,
+                1.000001072883606
+            ],
+            "min" : [
+                -1.000000238418579,
+                -1,
+                -1
+            ],
+            "type" : "VEC3"
+        },
+        {
+            "bufferView" : 1,
+            "componentType" : 5126,
+            "count" : 2143,
+            "type" : "VEC3"
+        },
+        {
+            "bufferView" : 2,
+            "componentType" : 5126,
+            "count" : 2143,
+            "type" : "VEC2"
+        },
+        {
+            "bufferView" : 3,
+            "componentType" : 5123,
+            "count" : 11904,
+            "type" : "SCALAR"
+        }
+    ],
+    "bufferViews" : [
+        {
+            "buffer" : 0,
+            "byteLength" : 25716,
+            "byteOffset" : 0
+        },
+        {
+            "buffer" : 0,
+            "byteLength" : 25716,
+            "byteOffset" : 25716
+        },
+        {
+            "buffer" : 0,
+            "byteLength" : 17144,
+            "byteOffset" : 51432
+        },
+        {
+            "buffer" : 0,
+            "byteLength" : 23808,
+            "byteOffset" : 68576
+        }
+    ],
+    "buffers" : [
+        {
+            "byteLength" : 92384,
+            "uri" : "sphere.bin"
+        }
+    ]
+}

crates/bevy_asset/Cargo.toml

@@ -4,6 +4,10 @@ version = "0.1.0"
 authors = ["Carter Anderson <mcanders1@gmail.com>"]
 edition = "2018"
 
+[features]
+default = ["filesystem_watcher"]
+filesystem_watcher = ["notify"]
+
 [dependencies]
 bevy_app = { path = "../bevy_app" }
 bevy_core = { path = "../bevy_core" }
@@ -12,4 +16,5 @@ legion = { path = "../bevy_legion" }
 uuid = { version = "0.8", features = ["v4", "serde"] }
 crossbeam-channel = "0.4.2"
 anyhow = "1.0"
-thiserror = "1.0"
+thiserror = "1.0"
+notify = { version = "5.0.0-pre.2", optional = true }

crates/bevy_asset/src/asset_path.rs

@@ -1,55 +0,0 @@
-use std::{
-    borrow::Cow,
-    path::{Path, PathBuf},
-};
-
-#[derive(Clone, Debug)]
-pub struct AssetPath {
-    pub path: Cow<'static, str>,
-    pub extension: Option<Cow<'static, str>>,
-}
-
-impl From<&Path> for AssetPath {
-    fn from(path: &Path) -> Self {
-        AssetPath {
-            path: Cow::Owned(
-                path.to_str()
-                    .expect("Path should be a valid string.")
-                    .to_string(),
-            ),
-            extension: path.extension().map(|e| {
-                Cow::Owned(
-                    e.to_str()
-                        .expect("Extension should be a valid string.")
-                        .to_string(),
-                )
-            }),
-        }
-    }
-}
-
-impl From<&PathBuf> for AssetPath {
-    fn from(path: &PathBuf) -> Self {
-        AssetPath {
-            path: Cow::Owned(
-                path.to_str()
-                    .expect("Path should be a valid string.")
-                    .to_string(),
-            ),
-            extension: path.extension().map(|e| {
-                Cow::Owned(
-                    e.to_str()
-                        .expect("Extension should be a valid string.")
-                        .to_string(),
-                )
-            }),
-        }
-    }
-}
-
-impl From<&str> for AssetPath {
-    fn from(path: &str) -> Self {
-        let path = Path::new(path);
-        AssetPath::from(path)
-    }
-}

crates/bevy_asset/src/asset_server.rs

@@ -1,13 +1,14 @@
 use crate::{
-    AssetLoadError, AssetLoadRequestHandler, AssetLoader, AssetPath, Assets, Handle, HandleId,
-    LoadRequest,
+    filesystem_watcher::FilesystemWatcher, AssetLoadError, AssetLoadRequestHandler, AssetLoader,
+    Assets, Handle, HandleId, LoadRequest,
 };
 use anyhow::Result;
-use legion::prelude::Resources;
+use crossbeam_channel::TryRecvError;
+use legion::prelude::{Res, Resources};
 use std::{
-    collections::HashMap,
+    collections::{HashMap, HashSet},
     env, fs, io,
-    path::Path,
+    path::{Path, PathBuf},
     sync::{Arc, RwLock},
     thread,
 };
@@ -27,6 +28,8 @@ pub enum AssetServerError {
     AssetLoadError(#[from] AssetLoadError),
     #[error("Encountered an io error.")]
     Io(#[from] io::Error),
+    #[error("Failed to watch asset folder.")]
+    AssetFolderWatchError { path: PathBuf },
 }
 
 struct LoaderThread {
@@ -36,7 +39,7 @@ struct LoaderThread {
 }
 
 pub struct AssetServer {
-    asset_folders: Vec<String>,
+    asset_folders: Vec<PathBuf>,
     loader_threads: RwLock<Vec<LoaderThread>>,
     max_loader_threads: usize,
     asset_handlers: Arc<RwLock<Vec<Box<dyn AssetLoadRequestHandler>>>>,
@@ -44,6 +47,9 @@ pub struct AssetServer {
     loaders: Vec<Resources>,
     extension_to_handler_index: HashMap<String, usize>,
     extension_to_loader_index: HashMap<String, usize>,
+    path_to_handle: RwLock<HashMap<PathBuf, HandleId>>,
+    #[cfg(feature = "filesystem_watcher")]
+    filesystem_watcher: Option<FilesystemWatcher>,
 }
 
 impl Default for AssetServer {
@@ -56,6 +62,9 @@ impl Default for AssetServer {
             loaders: Vec::new(),
             extension_to_handler_index: HashMap::new(),
             extension_to_loader_index: HashMap::new(),
+            path_to_handle: RwLock::new(HashMap::default()),
+            #[cfg(feature = "filesystem_watcher")]
+            filesystem_watcher: None,
         }
     }
 }
@@ -91,63 +100,139 @@ impl AssetServer {
         self.loaders.push(resources);
     }
 
-    pub fn add_asset_folder(&mut self, path: &str) {
-        self.asset_folders.push(path.to_string());
+    pub fn load_asset_folder<P: AsRef<Path>>(&mut self, path: P) -> Result<(), AssetServerError> {
+        let root_path = self.get_root_path()?;
+        let asset_folder = root_path.join(path);
+
+        #[cfg(feature = "filesystem_watcher")]
+        Self::watch_folder_for_changes(&mut self.filesystem_watcher, &asset_folder)?;
+
+        self.load_assets_in_folder_recursive(&asset_folder)?;
+        self.asset_folders.push(asset_folder);
+        Ok(())
     }
 
-    pub fn get_root_path(&self) -> Result<String, AssetServerError> {
-        if let Ok(manifest_dir) = env::var("CARGO_MANIFEST_DIR") {
-            Ok(manifest_dir)
-        } else {
-            match env::current_exe() {
-                Ok(exe_path) => exe_path
-                    .parent()
-                    .ok_or(AssetServerError::InvalidRootPath)
-                    .and_then(|exe_parent_path| {
-                        exe_parent_path
-                            .to_str()
-                            .map(|path| path.to_string())
-                            .ok_or(AssetServerError::InvalidRootPath)
-                    }),
-                Err(err) => Err(AssetServerError::Io(err)),
-            }
-        }
+    pub fn get_handle<T, P: AsRef<Path>>(&self, path: P) -> Option<Handle<T>> {
+        self.path_to_handle
+            .read()
+            .expect("RwLock poisoned")
+            .get(path.as_ref())
+            .map(|h| Handle::from(*h))
     }
 
-    pub fn load_assets(&self) -> Result<(), AssetServerError> {
-        let root_path_str = self.get_root_path()?;
-        let root_path = Path::new(&root_path_str);
-        for folder in self.asset_folders.iter() {
-            let asset_folder_path = root_path.join(folder);
-            self.load_assets_in_folder_recursive(&asset_folder_path)?;
+    #[cfg(feature = "filesystem_watcher")]
+    fn watch_folder_for_changes<P: AsRef<Path>>(
+        filesystem_watcher: &mut Option<FilesystemWatcher>,
+        path: P,
+    ) -> Result<(), AssetServerError> {
+        if let Some(watcher) = filesystem_watcher {
+            watcher.watch_folder(&path).map_err(|_error| {
+                AssetServerError::AssetFolderWatchError {
+                    path: path.as_ref().to_owned(),
+                }
+            })?;
         }
 
         Ok(())
     }
 
-    pub fn load<T>(&self, path: &str) -> Result<Handle<T>, AssetServerError> {
+    #[cfg(feature = "filesystem_watcher")]
+    pub fn watch_for_changes(&mut self) -> Result<(), AssetServerError> {
+        let _ = self
+            .filesystem_watcher
+            .get_or_insert_with(|| FilesystemWatcher::default());
+        for asset_folder in self.asset_folders.iter() {
+            Self::watch_folder_for_changes(&mut self.filesystem_watcher, asset_folder)?;
+        }
+
+        Ok(())
+    }
+
+    #[cfg(feature = "filesystem_watcher")]
+    pub fn filesystem_watcher_system(asset_server: Res<AssetServer>) {
+        use notify::event::{Event, EventKind, ModifyKind};
+        let mut changed = HashSet::new();
+        loop {
+            if let Some(ref filesystem_watcher) = asset_server.filesystem_watcher {
+                match filesystem_watcher.receiver.try_recv() {
+                    Ok(result) => {
+                        let event = result.unwrap();
+                        match event {
+                            Event {
+                                kind: EventKind::Modify(ModifyKind::Data(_)),
+                                paths,
+                                ..
+                            } => {
+                                for path in paths.iter() {
+                                    if !changed.contains(path) {
+                                        let root_path = asset_server.get_root_path().unwrap();
+                                        let relative_path = path.strip_prefix(root_path).unwrap();
+                                        match asset_server.load_untyped(relative_path) {
+                                            Ok(_) => {}
+                                            Err(AssetServerError::AssetLoadError(error)) => {
+                                                panic!("{:?}", error)
+                                            }
+                                            Err(_) => {}
+                                        }
+                                    }
+                                }
+                                changed.extend(paths);
+                            }
+                            _ => {}
+                        }
+                    }
+                    Err(TryRecvError::Empty) => {
+                        break;
+                    }
+                    Err(TryRecvError::Disconnected) => panic!("FilesystemWatcher disconnected"),
+                }
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn get_root_path(&self) -> Result<PathBuf, AssetServerError> {
+        if let Ok(manifest_dir) = env::var("CARGO_MANIFEST_DIR") {
+            Ok(PathBuf::from(manifest_dir))
+        } else {
+            match env::current_exe() {
+                Ok(exe_path) => exe_path
+                    .parent()
+                    .ok_or(AssetServerError::InvalidRootPath)
+                    .map(|exe_parent_path| exe_parent_path.to_owned()),
+                Err(err) => Err(AssetServerError::Io(err)),
+            }
+        }
+    }
+
+    pub fn load<T, P: AsRef<Path>>(&self, path: P) -> Result<Handle<T>, AssetServerError> {
         self.load_untyped(path)
             .map(|handle_id| Handle::from(handle_id))
     }
 
-    pub fn load_sync<T>(
+    pub fn load_sync<T, P: AsRef<Path>>(
         &self,
         assets: &mut Assets<T>,
-        path: &str,
+        path: P,
     ) -> Result<Handle<T>, AssetServerError>
     where
         T: 'static,
     {
-        let asset_path = AssetPath::from(path);
-        if let Some(ref extension) = asset_path.extension {
-            if let Some(index) = self.extension_to_loader_index.get(extension.as_ref()) {
+        let path = path.as_ref();
+        if let Some(ref extension) = path.extension() {
+            if let Some(index) = self.extension_to_loader_index.get(
+                extension
+                    .to_str()
+                    .expect("extension should be a valid string"),
+            ) {
                 let handle_id = HandleId::new();
                 let resources = &self.loaders[*index];
                 let loader = resources.get::<Box<dyn AssetLoader<T>>>().unwrap();
-                let asset = loader.load_from_file(&asset_path)?;
+                let asset = loader.load_from_file(path)?;
                 let handle = Handle::from(handle_id);
                 assets.set(handle, asset);
-                assets.set_path(handle, &asset_path.path);
+                assets.set_path(handle, path);
                 Ok(handle)
             } else {
                 Err(AssetServerError::MissingAssetHandler)
@@ -157,14 +242,28 @@ impl AssetServer {
         }
     }
 
-    pub fn load_untyped(&self, path: &str) -> Result<HandleId, AssetServerError> {
-        let asset_path = AssetPath::from(path);
-        if let Some(ref extension) = asset_path.extension {
-            if let Some(index) = self.extension_to_handler_index.get(extension.as_ref()) {
-                let handle_id = HandleId::new();
+    pub fn load_untyped<P: AsRef<Path>>(&self, path: P) -> Result<HandleId, AssetServerError> {
+        let path = path.as_ref();
+        if let Some(ref extension) = path.extension() {
+            if let Some(index) = self.extension_to_handler_index.get(
+                extension
+                    .to_str()
+                    .expect("Extension should be a valid string."),
+            ) {
+                let handle_id = {
+                    let mut path_to_handle = self.path_to_handle.write().expect("RwLock poisoned");
+                    if let Some(handle_id) = path_to_handle.get(path) {
+                        *handle_id
+                    } else {
+                        let handle_id = HandleId::new();
+                        path_to_handle.insert(path.to_owned(), handle_id.clone());
+                        handle_id
+                    }
+                };
+
                 self.send_request_to_loader_thread(LoadRequest {
                     handle_id,
-                    path: asset_path,
+                    path: path.to_owned(),
                     handler_index: *index,
                 });
                 Ok(handle_id)
@@ -232,12 +331,14 @@ impl AssetServer {
             ));
         }
 
-        for entry in fs::read_dir(&path)? {
+        let root_path = self.get_root_path()?;
+        for entry in fs::read_dir(path)? {
             let entry = entry?;
             let child_path = entry.path();
             if !child_path.is_dir() {
+                let relative_child_path = child_path.strip_prefix(&root_path).unwrap();
                 let _ =
-                    self.load_untyped(child_path.to_str().expect("Path should be a valid string"));
+                    self.load_untyped(relative_child_path.to_str().expect("Path should be a valid string"));
             } else {
                 self.load_assets_in_folder_recursive(&child_path)?;
             }

crates/bevy_asset/src/assets.rs

@@ -5,7 +5,7 @@ use crate::{
 use bevy_app::{stage, AppBuilder, Events};
 use bevy_core::bytes::GetBytes;
 use legion::prelude::*;
-use std::collections::HashMap;
+use std::{path::{Path, PathBuf}, collections::HashMap};
 
 pub enum AssetEvent<T> {
     Created { handle: Handle<T> },
@@ -14,7 +14,7 @@ pub enum AssetEvent<T> {
 
 pub struct Assets<T> {
     assets: HashMap<HandleId, T>,
-    paths: HashMap<String, Handle<T>>,
+    paths: HashMap<PathBuf, Handle<T>>,
     events: Events<AssetEvent<T>>,
 }
 
@@ -29,8 +29,8 @@ impl<T> Default for Assets<T> {
 }
 
 impl<T> Assets<T> {
-    pub fn get_with_path(&mut self, path: &str) -> Option<Handle<T>> {
-        self.paths.get(path).map(|handle| *handle)
+    pub fn get_with_path<P: AsRef<Path>>(&mut self, path: P) -> Option<Handle<T>> {
+        self.paths.get(path.as_ref()).map(|handle| *handle)
     }
 
     pub fn add(&mut self, asset: T) -> Handle<T> {
@@ -64,8 +64,8 @@ impl<T> Assets<T> {
         handle
     }
 
-    pub fn set_path(&mut self, handle: Handle<T>, path: &str) {
-        self.paths.insert(path.to_string(), handle);
+    pub fn set_path<P: AsRef<Path>>(&mut self, handle: Handle<T>, path: P) {
+        self.paths.insert(path.as_ref().to_owned(), handle);
     }
 
     pub fn get_id(&self, id: HandleId) -> Option<&T> {

crates/bevy_asset/src/filesystem_watcher.rs

@@ -0,0 +1,26 @@
+use crossbeam_channel::Receiver;
+use notify::{Event, RecommendedWatcher, RecursiveMode, Result, Watcher};
+use std::path::Path;
+
+/// Watches for changes to assets on the filesystem and informs the `AssetServer` to reload them
+pub struct FilesystemWatcher {
+    pub watcher: RecommendedWatcher,
+    pub receiver: Receiver<Result<Event>>,
+}
+
+impl Default for FilesystemWatcher {
+    fn default() -> Self {
+        let (sender, receiver) = crossbeam_channel::unbounded();
+        let watcher: RecommendedWatcher = Watcher::new_immediate(move |res| {
+            sender.send(res).expect("Watch event send failure");
+        })
+        .expect("Failed to create filesystem watcher");
+        FilesystemWatcher { watcher, receiver }
+    }
+}
+
+impl FilesystemWatcher {
+    pub fn watch_folder<P: AsRef<Path>>(&mut self, path: P) -> Result<()> {
+        self.watcher.watch(path, RecursiveMode::Recursive)
+    }
+}

crates/bevy_asset/src/lib.rs

@@ -1,11 +1,11 @@
-mod asset_path;
 mod asset_server;
 mod assets;
 mod handle;
 mod load_request;
 mod loader;
+#[cfg(feature = "filesystem_watcher")]
+pub mod filesystem_watcher;
 
-pub use asset_path::*;
 pub use asset_server::*;
 pub use assets::*;
 pub use handle::*;
@@ -13,6 +13,7 @@ pub use load_request::*;
 pub use loader::*;
 
 use bevy_app::{AppBuilder, AppPlugin};
+use legion::prelude::IntoSystem;
 
 pub mod stage {
     pub const LOAD_ASSETS: &str = "load_assets";
@@ -23,7 +24,9 @@ pub struct AssetPlugin;
 
 impl AppPlugin for AssetPlugin {
     fn build(&self, app: &mut AppBuilder) {
-        app.add_stage(stage::LOAD_ASSETS)
+        app.add_stage_before(bevy_app::stage::PRE_UPDATE,  stage::LOAD_ASSETS)
             .init_resource::<AssetServer>();
+        #[cfg(feature = "filesystem_watcher")]
+        app.add_system_to_stage(stage::LOAD_ASSETS, AssetServer::filesystem_watcher_system.system());
     }
-}
+}

crates/bevy_asset/src/load_request.rs

@@ -1,13 +1,13 @@
-use crate::{AssetLoadError, AssetLoader, AssetPath, AssetResult, Handle, HandleId};
+use crate::{AssetLoadError, AssetLoader, AssetResult, Handle, HandleId};
 use anyhow::Result;
 use crossbeam_channel::Sender;
 use fs::File;
 use io::Read;
-use std::{fs, io, path::Path};
+use std::{fs, io, path::PathBuf};
 
 #[derive(Debug)]
 pub struct LoadRequest {
-    pub path: AssetPath,
+    pub path: PathBuf,
     pub handle_id: HandleId,
     pub handler_index: usize,
 }
@@ -34,7 +34,7 @@ where
     }
 
     fn load_asset(&self, load_request: &LoadRequest) -> Result<TAsset, AssetLoadError> {
-        let mut file = File::open(Path::new(load_request.path.path.as_ref()))?;
+        let mut file = File::open(&load_request.path)?;
         let mut bytes = Vec::new();
         file.read_to_end(&mut bytes)?;
         let asset = self.loader.from_bytes(&load_request.path, bytes)?;

crates/bevy_asset/src/loader.rs

@@ -1,10 +1,13 @@
-use crate::{AssetPath, Assets, Handle};
+use crate::{Assets, Handle};
 use anyhow::Result;
 use crossbeam_channel::{Receiver, Sender, TryRecvError};
 use fs::File;
 use io::Read;
 use legion::prelude::{Res, ResMut};
-use std::{fs, io, path::Path};
+use std::{
+    fs, io,
+    path::{Path, PathBuf},
+};
 use thiserror::Error;
 
 #[derive(Error, Debug)]
@@ -16,10 +19,10 @@ pub enum AssetLoadError {
 }
 
 pub trait AssetLoader<T>: Send + Sync + 'static {
-    fn from_bytes(&self, asset_path: &AssetPath, bytes: Vec<u8>) -> Result<T, anyhow::Error>;
+    fn from_bytes(&self, asset_path: &Path, bytes: Vec<u8>) -> Result<T, anyhow::Error>;
     fn extensions(&self) -> &[&str];
-    fn load_from_file(&self, asset_path: &AssetPath) -> Result<T, AssetLoadError> {
-        let mut file = File::open(Path::new(asset_path.path.as_ref()))?;
+    fn load_from_file(&self, asset_path: &Path) -> Result<T, AssetLoadError> {
+        let mut file = File::open(asset_path)?;
         let mut bytes = Vec::new();
         file.read_to_end(&mut bytes)?;
         let asset = self.from_bytes(asset_path, bytes)?;
@@ -30,7 +33,7 @@ pub trait AssetLoader<T>: Send + Sync + 'static {
 pub struct AssetResult<T> {
     pub result: Result<T, AssetLoadError>,
     pub handle: Handle<T>,
-    pub path: AssetPath,
+    pub path: PathBuf,
 }
 
 pub struct AssetChannel<T> {
@@ -54,7 +57,7 @@ pub fn update_asset_storage_system<T>(
             Ok(result) => {
                 let asset = result.result.unwrap();
                 assets.set(result.handle, asset);
-                assets.set_path(result.handle, &result.path.path);
+                assets.set_path(result.handle, &result.path);
             }
             Err(TryRecvError::Empty) => {
                 break;

crates/bevy_gltf/src/loader.rs

@@ -4,7 +4,7 @@ use bevy_render::{
 };
 
 use anyhow::Result;
-use bevy_asset::{AssetLoader, AssetPath};
+use bevy_asset::AssetLoader;
 use gltf::{buffer::Source, iter, mesh::Mode};
 use std::{fs, io, path::Path};
 use thiserror::Error;
@@ -13,7 +13,7 @@ use thiserror::Error;
 pub struct GltfLoader;
 
 impl AssetLoader<Mesh> for GltfLoader {
-    fn from_bytes(&self, asset_path: &AssetPath, bytes: Vec<u8>) -> Result<Mesh> {
+    fn from_bytes(&self, asset_path: &Path, bytes: Vec<u8>) -> Result<Mesh> {
         let mesh = load_gltf(asset_path, bytes)?;
         Ok(mesh)
     }
@@ -46,7 +46,7 @@ fn get_primitive_topology(mode: Mode) -> Result<PrimitiveTopology, GltfError> {
     }
 }
 
-pub fn load_gltf(asset_path: &AssetPath, bytes: Vec<u8>) -> Result<Mesh, GltfError> {
+pub fn load_gltf(asset_path: &Path, bytes: Vec<u8>) -> Result<Mesh, GltfError> {
     let gltf = gltf::Gltf::from_slice(&bytes)?;
     let buffer_data = load_buffers(gltf.buffers(), asset_path)?;
     for scene in gltf.scenes() {
@@ -104,15 +104,14 @@ fn load_node(buffer_data: &[Vec<u8>], node: &gltf::Node, depth: i32) -> Result<M
     panic!("failed to find mesh")
 }
 
-fn load_buffers(buffers: iter::Buffers, asset_path: &AssetPath) -> Result<Vec<Vec<u8>>, GltfError> {
+fn load_buffers(buffers: iter::Buffers, asset_path: &Path) -> Result<Vec<Vec<u8>>, GltfError> {
     let mut buffer_data = Vec::new();
     for buffer in buffers {
         match buffer.source() {
             Source::Uri(uri) => {
                 if uri.starts_with("data:") {
                 } else {
-                    let path = Path::new(asset_path.path.as_ref());
-                    let buffer_path = path.parent().unwrap().join(uri);
+                    let buffer_path = asset_path.parent().unwrap().join(uri);
                     let buffer_bytes = fs::read(buffer_path)?;
                     buffer_data.push(buffer_bytes);
                 }

crates/bevy_render/src/mesh.rs

@@ -3,8 +3,8 @@ use crate::{
         state_descriptors::{IndexFormat, PrimitiveTopology},
         VertexBufferDescriptor, VertexBufferDescriptors, VertexFormat,
     },
-    render_resource::{BufferInfo, BufferUsage, EntitiesWaitingForAssets},
-    renderer::{RenderResourceContext, RenderResources},
+    render_resource::{BufferInfo, BufferUsage},
+    renderer::RenderResources,
     shader::AsUniforms,
     Renderable, Vertex,
 };

crates/bevy_render/src/texture/png_texture_loader.rs

@@ -1,12 +1,13 @@
 use super::Texture;
 use anyhow::Result;
-use bevy_asset::{AssetLoader, AssetPath};
+use bevy_asset::AssetLoader;
+use std::path::Path;
 
 #[derive(Clone, Default)]
 pub struct PngTextureLoader;
 
 impl AssetLoader<Texture> for PngTextureLoader {
-    fn from_bytes(&self, _asset_path: &AssetPath, bytes: Vec<u8>) -> Result<Texture> {
+    fn from_bytes(&self, _asset_path: &Path, bytes: Vec<u8>) -> Result<Texture> {
         let decoder = png::Decoder::new(bytes.as_slice());
         let (info, mut reader) = decoder.read_info()?;
         let mut data = vec![0; info.buffer_size()];

crates/bevy_text/src/font_loader.rs

@@ -1,12 +1,13 @@
 use crate::Font;
 use anyhow::Result;
-use bevy_asset::{AssetLoader, AssetPath};
+use bevy_asset::AssetLoader;
+use std::path::Path;
 
 #[derive(Clone)]
 pub struct FontLoader;
 
 impl AssetLoader<Font> for FontLoader {
-    fn from_bytes(&self, _asset_path: &AssetPath, bytes: Vec<u8>) -> Result<Font> {
+    fn from_bytes(&self, _asset_path: &Path, bytes: Vec<u8>) -> Result<Font> {
         Ok(Font::try_from_bytes(bytes)?)
     }
     fn extensions(&self) -> &[&str] {

examples/asset/asset_loading.rs

@@ -0,0 +1,80 @@
+use bevy::prelude::*;
+use bevy_asset::AssetServer;
+
+fn main() {
+    App::build()
+        .add_default_plugins()
+        .add_startup_system(setup.system())
+        .run();
+}
+
+fn setup(
+    command_buffer: &mut CommandBuffer,
+    mut asset_server: ResMut<AssetServer>,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+) {
+    // You can load all assets in a folder like this. they will be loaded in parallel without blocking
+    asset_server.load_asset_folder("assets/models/monkey").unwrap();
+
+    // Then any asset in the folder can be accessed like this:
+    let monkey_handle = asset_server
+        .get_handle("assets/models/monkey/Monkey.gltf")
+        .unwrap();
+
+    // You can load individual assets like this:
+    let cube_handle = asset_server
+        .load("assets/models/cube/cube.gltf")
+        .unwrap();
+   
+    // Assets are loaded in the background by default, which means they might not be available immediately after loading.
+    // If you need immediate access you can load assets synchronously like this:
+    let sphere_handle = asset_server.load_sync(&mut meshes, "assets/models/sphere/sphere.gltf").unwrap();
+    let sphere = meshes.get(&sphere_handle).unwrap();
+    println!("{:?}", sphere.primitive_topology);
+
+    // You can also add assets directly to their Assets<T> storage
+    let material_handle = materials.add(StandardMaterial {
+        albedo: Color::rgb(0.5, 0.4, 0.3),
+        ..Default::default()
+    });
+
+    // add entities to the world
+    command_buffer
+        .build()
+        // monkey
+        .add_entity(MeshEntity {
+            mesh: monkey_handle,
+            material: material_handle,
+            translation: Translation::new(-3.0, 0.0, 0.0),
+            ..Default::default()
+        })
+        // cube
+        .add_entity(MeshEntity {
+            mesh: cube_handle,
+            material: material_handle,
+            translation: Translation::new(0.0, 0.0, 0.0),
+            ..Default::default()
+        })
+        // sphere
+        .add_entity(MeshEntity {
+            mesh: sphere_handle,
+            material: material_handle,
+            translation: Translation::new(3.0, 0.0, 0.0),
+            ..Default::default()
+        })
+        // light
+        .add_entity(LightEntity {
+            translation: Translation::new(4.0, -4.0, 5.0),
+            ..Default::default()
+        })
+        // camera
+        .add_entity(CameraEntity {
+            local_to_world: LocalToWorld(Mat4::look_at_rh(
+                Vec3::new(0.0, -10.0, 3.0),
+                Vec3::new(0.0, 0.0, 0.0),
+                Vec3::new(0.0, 0.0, 1.0),
+            )),
+            ..Default::default()
+        });
+}

examples/asset/hot_asset_reload.rs

@@ -0,0 +1,60 @@
+use bevy::prelude::*;
+use bevy_asset::AssetServer;
+
+/// 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.
+fn main() {
+    App::build()
+        .add_default_plugins()
+        .add_startup_system(setup.system())
+        .run();
+}
+
+fn setup(
+    command_buffer: &mut CommandBuffer,
+    mut asset_server: ResMut<AssetServer>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+) {
+    // load an asset folder
+    asset_server.load_asset_folder("assets").unwrap();
+
+    // tell the asset server to watch for changes
+    asset_server.watch_for_changes().unwrap();
+
+    // load the mesh
+    let mesh_handle = asset_server
+        .get_handle("assets/models/monkey/Monkey.gltf")
+        .unwrap();
+
+    // now any changes to the mesh will be reloaded automatically!
+
+    // create a material for the mesh
+    let material_handle = materials.add(StandardMaterial {
+        albedo: Color::rgb(0.5, 0.4, 0.3),
+        ..Default::default()
+    });
+
+    // add entities to the world
+    command_buffer
+        .build()
+        // mesh
+        .add_entity(MeshEntity {
+            mesh: mesh_handle,
+            material: material_handle,
+            ..Default::default()
+        })
+        // light
+        .add_entity(LightEntity {
+            translation: Translation::new(4.0, -4.0, 5.0),
+            ..Default::default()
+        })
+        // camera
+        .add_entity(CameraEntity {
+            local_to_world: LocalToWorld(Mat4::look_at_rh(
+                Vec3::new(2.0, -6.0, 2.0),
+                Vec3::new(0.0, 0.0, 0.0),
+                Vec3::new(0.0, 0.0, 1.0),
+            )),
+            ..Default::default()
+        });
+}

examples/asset/load_asset_folder.rs

@@ -1,13 +0,0 @@
-use bevy::{asset::AssetServer, prelude::*};
-
-fn main() {
-    App::build()
-        .add_default_plugins()
-        .add_startup_system(setup.system())
-        .run();
-}
-
-fn setup(mut asset_server: ResMut<AssetServer>) {
-    asset_server.add_asset_folder("assets");
-    asset_server.load_assets().expect("Assets should exist");
-}