1 commit

Author	SHA1	Message	Date
Carter Anderson	35073cf7aa	Multiple Asset Sources (#9885) ... This adds support for **Multiple Asset Sources**. You can now register a named `AssetSource`, which you can load assets from like you normally would: ```rust let shader: Handle<Shader> = asset_server.load("custom_source://path/to/shader.wgsl"); ``` Notice that `AssetPath` now supports `some_source://` syntax. This can now be accessed through the `asset_path.source()` accessor. Asset source names _are not required_. If one is not specified, the default asset source will be used: ```rust let shader: Handle<Shader> = asset_server.load("path/to/shader.wgsl"); ``` The behavior of the default asset source has not changed. Ex: the `assets` folder is still the default. As referenced in #9714 ## Why? **Multiple Asset Sources** enables a number of often-asked-for scenarios: * **Loading some assets from other locations on disk**: you could create a `config` asset source that reads from the OS-default config folder (not implemented in this PR) * **Loading some assets from a remote server**: you could register a new `remote` asset source that reads some assets from a remote http server (not implemented in this PR) * **Improved "Binary Embedded" Assets**: we can use this system for "embedded-in-binary assets", which allows us to replace the old `load_internal_asset!` approach, which couldn't support asset processing, didn't support hot-reloading _well_, and didn't make embedded assets accessible to the `AssetServer` (implemented in this pr) ## Adding New Asset Sources An `AssetSource` is "just" a collection of `AssetReader`, `AssetWriter`, and `AssetWatcher` entries. You can configure new asset sources like this: ```rust app.register_asset_source( "other", AssetSource::build() .with_reader(|| Box::new(FileAssetReader::new("other"))) ) ) ``` Note that `AssetSource` construction _must_ be repeatable, which is why a closure is accepted. `AssetSourceBuilder` supports `with_reader`, `with_writer`, `with_watcher`, `with_processed_reader`, `with_processed_writer`, and `with_processed_watcher`. Note that the "asset source" system replaces the old "asset providers" system. ## Processing Multiple Sources The `AssetProcessor` now supports multiple asset sources! Processed assets can refer to assets in other sources and everything "just works". Each `AssetSource` defines an unprocessed and processed `AssetReader` / `AssetWriter`. Currently this is all or nothing for a given `AssetSource`. A given source is either processed or it is not. Later we might want to add support for "lazy asset processing", where an `AssetSource` (such as a remote server) can be configured to only process assets that are directly referenced by local assets (in order to save local disk space and avoid doing extra work). ## A new `AssetSource`: `embedded` One of the big features motivating **Multiple Asset Sources** was improving our "embedded-in-binary" asset loading. To prove out the **Multiple Asset Sources** implementation, I chose to build a new `embedded` `AssetSource`, which replaces the old `load_interal_asset!` system. The old `load_internal_asset!` approach had a number of issues: * The `AssetServer` was not aware of (or capable of loading) internal assets. * Because internal assets weren't visible to the `AssetServer`, they could not be processed (or used by assets that are processed). This would prevent things "preprocessing shaders that depend on built in Bevy shaders", which is something we desperately need to start doing. * Each "internal asset" needed a UUID to be defined in-code to reference it. This was very manual and toilsome. The new `embedded` `AssetSource` enables the following pattern: ```rust // Called in `crates/bevy_pbr/src/render/mesh.rs` embedded_asset!(app, "mesh.wgsl"); // later in the app let shader: Handle<Shader> = asset_server.load("embedded://bevy_pbr/render/mesh.wgsl"); ``` Notice that this always treats the crate name as the "root path", and it trims out the `src` path for brevity. This is generally predictable, but if you need to debug you can use the new `embedded_path!` macro to get a `PathBuf` that matches the one used by `embedded_asset`. You can also reference embedded assets in arbitrary assets, such as WGSL shaders: ```rust #import "embedded://bevy_pbr/render/mesh.wgsl" ``` This also makes `embedded` assets go through the "normal" asset lifecycle. They are only loaded when they are actually used! We are also discussing implicitly converting asset paths to/from shader modules, so in the future (not in this PR) you might be able to load it like this: ```rust #import bevy_pbr::render::mesh::Vertex ``` Compare that to the old system! ```rust pub const MESH_SHADER_HANDLE: Handle<Shader> = Handle::weak_from_u128(3252377289100772450); load_internal_asset!(app, MESH_SHADER_HANDLE, "mesh.wgsl", Shader::from_wgsl); // The mesh asset is the _only_ accessible via MESH_SHADER_HANDLE and _cannot_ be loaded via the AssetServer. ``` ## Hot Reloading `embedded` You can enable `embedded` hot reloading by enabling the `embedded_watcher` cargo feature: ``` cargo run --features=embedded_watcher ``` ## Improved Hot Reloading Workflow First: the `filesystem_watcher` cargo feature has been renamed to `file_watcher` for brevity (and to match the `FileAssetReader` naming convention). More importantly, hot asset reloading is no longer configured in-code by default. If you enable any asset watcher feature (such as `file_watcher` or `rust_source_watcher`), asset watching will be automatically enabled. This removes the need to _also_ enable hot reloading in your app code. That means you can replace this: ```rust app.add_plugins(DefaultPlugins.set(AssetPlugin::default().watch_for_changes())) ``` with this: ```rust app.add_plugins(DefaultPlugins) ``` If you want to hot reload assets in your app during development, just run your app like this: ``` cargo run --features=file_watcher ``` This means you can use the same code for development and deployment! To deploy an app, just don't include the watcher feature ``` cargo build --release ``` My intent is to move to this approach for pretty much all dev workflows. In a future PR I would like to replace `AssetMode::ProcessedDev` with a `runtime-processor` cargo feature. We could then group all common "dev" cargo features under a single `dev` feature: ```sh # this would enable file_watcher, embedded_watcher, runtime-processor, and more cargo run --features=dev ``` ## AssetMode `AssetPlugin::Unprocessed`, `AssetPlugin::Processed`, and `AssetPlugin::ProcessedDev` have been replaced with an `AssetMode` field on `AssetPlugin`. ```rust // before app.add_plugins(DefaultPlugins.set(AssetPlugin::Processed { /* fields here */ }) // after app.add_plugins(DefaultPlugins.set(AssetPlugin { mode: AssetMode::Processed, ..default() }) ``` This aligns `AssetPlugin` with our other struct-like plugins. The old "source" and "destination" `AssetProvider` fields in the enum variants have been replaced by the "asset source" system. You no longer need to configure the AssetPlugin to "point" to custom asset providers. ## AssetServerMode To improve the implementation of **Multiple Asset Sources**, `AssetServer` was made aware of whether or not it is using "processed" or "unprocessed" assets. You can check that like this: ```rust if asset_server.mode() == AssetServerMode::Processed { /* do something */ } ``` Note that this refactor should also prepare the way for building "one to many processed output files", as it makes the server aware of whether it is loading from processed or unprocessed sources. Meaning we can store and read processed and unprocessed assets differently! ## AssetPath can now refer to folders The "file only" restriction has been removed from `AssetPath`. The `AssetServer::load_folder` API now accepts an `AssetPath` instead of a `Path`, meaning you can load folders from other asset sources! ## Improved AssetPath Parsing AssetPath parsing was reworked to support sources, improve error messages, and to enable parsing with a single pass over the string. `AssetPath::new` was replaced by `AssetPath::parse` and `AssetPath::try_parse`. ## AssetWatcher broken out from AssetReader `AssetReader` is no longer responsible for constructing `AssetWatcher`. This has been moved to `AssetSourceBuilder`. ## Duplicate Event Debouncing Asset V2 already debounced duplicate filesystem events, but this was _input_ events. Multiple input event types can produce the same _output_ `AssetSourceEvent`. Now that we have `embedded_watcher`, which does expensive file io on events, it made sense to debounce output events too, so I added that! This will also benefit the AssetProcessor by preventing integrity checks for duplicate events (and helps keep the noise down in trace logs). ## Next Steps * **Port Built-in Shaders**: Currently the primary (and essentially only) user of `load_interal_asset` in Bevy's source code is "built-in shaders". I chose not to do that in this PR for a few reasons: 1. We need to add the ability to pass shader defs in to shaders via meta files. Some shaders (such as MESH_VIEW_TYPES) need to pass shader def values in that are defined in code. 2. We need to revisit the current shader module naming system. I think we _probably_ want to imply modules from source structure (at least by default). Ideally in a way that can losslessly convert asset paths to/from shader modules (to enable the asset system to resolve modules using the asset server). 3. I want to keep this change set minimal / get this merged first. * **Deprecate `load_internal_asset`**: we can't do that until we do (1) and (2) * **Relative Asset Paths**: This PR significantly increases the need for relative asset paths (which was already pretty high). Currently when loading dependencies, it is assumed to be an absolute path, which means if in an `AssetLoader` you call `context.load("some/path/image.png")` it will assume that is the "default" asset source, _even if the current asset is in a different asset source_. This will cause breakage for AssetLoaders that are not designed to add the current source to whatever paths are being used. AssetLoaders should generally not need to be aware of the name of their current asset source, or need to think about the "current asset source" generally. We should build apis that support relative asset paths and then encourage using relative paths as much as possible (both via api design and docs). Relative paths are also important because they will allow developers to move folders around (even across providers) without reprocessing, provided there is no path breakage.	2023-10-13 23:17:32 +00:00