# Examples These examples demonstrate the main features of Bevy and how to use them. To run an example, use the command `cargo run --example `, and add the option `--features x11` or `--features wayland` to force the example to run on a specific window compositor, e.g. ```sh cargo run --features wayland --example hello_world ``` **⚠️ Note: for users of releases on crates.io!** There are often large differences and incompatible API changes between the latest [crates.io](https://crates.io/crates/bevy) release and the development version of Bevy in the git main branch! If you are using a released version of bevy, you need to make sure you are viewing the correct version of the examples! - Latest release: [https://github.com/bevyengine/bevy/tree/latest/examples](https://github.com/bevyengine/bevy/tree/latest/examples) - Specific version, such as `0.4`: [https://github.com/bevyengine/bevy/tree/v0.4.0/examples](https://github.com/bevyengine/bevy/tree/v0.4.0/examples) When you clone the repo locally to run the examples, use `git checkout` to get the correct version: ```bash # `latest` always points to the newest release git checkout latest # or use a specific version git checkout v0.4.0 ``` --- ## Table of Contents - [Examples](#examples) - [Table of Contents](#table-of-contents) - [The Bare Minimum](#the-bare-minimum) - [Hello, World!](#hello-world) - [Cross-Platform Examples](#cross-platform-examples) {% for category, _ in all_examples %} - [{{ category }}](#{{ category | slugify }}) {% endfor %} - [Tests](#tests) - [Platform-Specific Examples](#platform-specific-examples) - [Android](#android) - [Setup](#setup) - [Build & Run](#build--run) - [Old phones](#old-phones) - [iOS](#ios) - [Setup](#setup-1) - [Build & Run](#build--run-1) - [WASM](#wasm) - [Setup](#setup-2) - [Build & Run](#build--run-2) - [Loading Assets](#loading-assets) # The Bare Minimum ## Hello, World! Example | Description --- | --- [`hello_world.rs`](./hello_world.rs) | Runs a minimal example that outputs "hello world" # Cross-Platform Examples {% for category, details in all_examples %} ## {{ category }} {% if details.description is string %}{{ details.description }} {% endif %}Example | Description --- | --- {% for example in details.examples %}[{{ example.name }}](../{{ example.path }}) | {{ example.description }} {% endfor %}{% endfor %} # Tests Example | Description --- | --- [How to Test Systems](../tests/how_to_test_systems.rs) | How to test systems with commands, queries or resources # Platform-Specific Examples ## Android ### Setup ```sh rustup target add aarch64-linux-android armv7-linux-androideabi cargo install cargo-apk ``` The Android SDK must be installed, and the environment variable `ANDROID_SDK_ROOT` set to the root Android `sdk` folder. When using `NDK (Side by side)`, the environment variable `ANDROID_NDK_ROOT` must also be set to one of the NDKs in `sdk\ndk\[NDK number]`. ### Build & Run To run on a device setup for Android development, run: ```sh cargo apk run --example android_example ``` When using Bevy as a library, the following fields must be added to `Cargo.toml`: ```toml [package.metadata.android] build_targets = ["aarch64-linux-android", "armv7-linux-androideabi"] [package.metadata.android.sdk] target_sdk_version = 31 ``` Please reference `cargo-apk` [README](https://crates.io/crates/cargo-apk) for other Android Manifest fields. ### Debugging You can view the logs with the following command: ```sh adb logcat | grep 'RustStdoutStderr\|bevy\|wgpu' ``` In case of an error getting a GPU or setting it up, you can try settings logs of `wgpu_hal` to `DEBUG` to get more informations. Sometimes, running the app complains about an unknown activity. This may be fixed by uninstalling the application: ```sh adb uninstall org.bevyengine.example ``` ### Old phones Bevy by default targets Android API level 31 in its examples which is the [Play Store's minimum API to upload or update apps](https://developer.android.com/distribute/best-practices/develop/target-sdk). Users of older phones may want to use an older API when testing. To use a different API, the following fields must be updated in Cargo.toml: ```toml [package.metadata.android.sdk] target_sdk_version = >>API<< min_sdk_version = >>API or less<< ``` Example | File | Description --- | --- | --- `android` | [`android/android.rs`](./android/android.rs) | The `3d/3d_scene.rs` example for Android ## iOS ### Setup You need to install the correct rust targets: - `aarch64-apple-ios`: iOS devices - `x86_64-apple-ios`: iOS simulator on x86 processors - `aarch64-apple-ios-sim`: iOS simulator on Apple processors ```sh rustup target add aarch64-apple-ios x86_64-apple-ios aarch64-apple-ios-sim ``` ### Build & Run Using bash: ```sh cd examples/ios make run ``` In an ideal world, this will boot up, install and run the app for the first iOS simulator in your `xcrun simctl devices list`. If this fails, you can specify the simulator device UUID via: ```sh DEVICE_ID=${YOUR_DEVICE_ID} make run ``` If you'd like to see xcode do stuff, you can run ```sh open bevy_ios_example.xcodeproj/ ``` which will open xcode. You then must push the zoom zoom play button and wait for the magic. Example | File | Description --- | --- | --- `ios` | [`ios/src/lib.rs`](./ios/src/lib.rs) | The `3d/3d_scene.rs` example for iOS ## WASM ### Setup ```sh rustup target add wasm32-unknown-unknown cargo install wasm-bindgen-cli ``` ### Build & Run Following is an example for `lighting`. For other examples, change the `lighting` in the following commands. ```sh cargo build --release --example lighting --target wasm32-unknown-unknown wasm-bindgen --out-name wasm_example \ --out-dir examples/wasm/target \ --target web target/wasm32-unknown-unknown/release/examples/lighting.wasm ``` The first command will build the example for the wasm target, creating a binary. Then, [wasm-bindgen-cli](https://rustwasm.github.io/wasm-bindgen/reference/cli.html) is used to create javascript bindings to this wasm file, which can be loaded using this [example HTML file](./wasm/index.html). Then serve `examples/wasm` directory to browser. i.e. ```sh # cargo install basic-http-server basic-http-server examples/wasm # with python python3 -m http.server --directory examples/wasm # with ruby ruby -run -ehttpd examples/wasm ``` ### Optimizing On the web, it's useful to reduce the size of the files that are distributed. With rust, there are many ways to improve your executable sizes. Here are some. #### 1. Tweak your `Cargo.toml` Add a new [profile](https://doc.rust-lang.org/cargo/reference/profiles.html) to your `Cargo.toml`: ```toml [profile.wasm-release] # Use release profile as default values inherits = "release" # Optimize with size in mind, also try "s", sometimes it is better. # This doesn't increase compilation times compared to -O3, great improvements opt-level = "z" # Do a second optimization pass removing duplicate or unused code from dependencies. # Slows compile times, marginal improvements lto = "fat" # When building crates, optimize larger chunks at a time # Slows compile times, marginal improvements codegen-units = 1 ``` Now, when building the final executable, use the `wasm-release` profile by replacing `--release` by `--profile wasm-release` in the cargo command. ```sh cargo build --profile wasm-release --example lighting --target wasm32-unknown-unknown ``` Make sure your final executable size is smaller, some of those optimizations may not be worth keeping, due to compilation time increases. #### 2. Use `wasm-opt` from the binaryen package Binaryen is a set of tools for working with wasm. It has a `wasm-opt` CLI tool. First download the `binaryen` package, then locate the `.wasm` file generated by `wasm-bindgen`. It should be in the `--out-dir` you specified in the command line, the file name should end in `_bg.wasm`. Then run `wasm-opt` with the `-Oz` flag. Note that `wasm-opt` is _very slow_. Note that `wasm-opt` optimizations might not be as effective if you didn't apply the optimizations from the previous section. ```sh wasm-opt -Oz --output optimized.wasm examples/wasm/target/lighting_bg.wasm mv optimized.wasm examples/wasm/target/lighting_bg.wasm ``` For a small project with a basic 3d model and two lights, the generated file sizes are, as of Jully 2022 as following: |profile | wasm-opt | no wasm-opt | |----------------------------------|----------|-------------| |Default | 8.5M | 13.0M | |opt-level = "z" | 6.1M | 12.7M | |"z" + lto = "thin" | 5.9M | 12M | |"z" + lto = "fat" | 5.1M | 9.4M | |"z" + "thin" + codegen-units = 1 | 5.3M | 11M | |"z" + "fat" + codegen-units = 1 | 4.8M | 8.5M | There are more advanced optimization options available, check the following pages for more info: - - - ### Loading Assets To load assets, they need to be available in the folder examples/wasm/assets. Cloning this repository will set it up as a symlink on Linux and macOS, but you will need to manually move the assets on Windows.