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README.md

Examples

These examples demonstrate the main features of Bevy and how to use them. To run an example, use the command cargo run --example <Example>, and add the option --features x11 or --features wayland to force the example to run on a specific window compositor, e.g.

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 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!

When you clone the repo locally to run the examples, use git checkout to get the correct version:

# `latest` always points to the newest release
git checkout latest
# or use a specific version
git checkout v0.4.0

Table of Contents

The Bare Minimum

Hello, World!

Example Description
hello_world.rs Runs a minimal example that outputs "hello world"

Cross-Platform Examples

2D Rendering

Example Description
2D Bloom Illustrates bloom post-processing in 2d
2D Bounding Volume Intersections Showcases bounding volumes and intersection tests
2D Rotation Demonstrates rotating entities in 2D with quaternions
2D Shapes Renders simple 2D primitive shapes like circles and polygons
2D Viewport To World Demonstrates how to use the Camera::viewport_to_world_2d method
2D Wireframe Showcases wireframes for 2d meshes
Arc 2D Meshes Demonstrates UV-mapping of the circular segment and sector primitives
CPU Drawing Manually read/write the pixels of a texture
Custom glTF vertex attribute 2D Renders a glTF mesh in 2D with a custom vertex attribute
Manual Mesh 2D Renders a custom mesh "manually" with "mid-level" renderer apis
Mesh 2D Renders a 2d mesh
Mesh 2D With Vertex Colors Renders a 2d mesh with vertex color attributes
Mesh2d Alpha Mode Used to test alpha modes with mesh2d
Move Sprite Changes the transform of a sprite
Pixel Grid Snapping Shows how to create graphics that snap to the pixel grid by rendering to a texture in 2D
Sprite Renders a sprite
Sprite Animation Animates a sprite in response to an event
Sprite Flipping Renders a sprite flipped along an axis
Sprite Sheet Renders an animated sprite
Sprite Slice Showcases slicing sprites into sections that can be scaled independently via the 9-patch technique
Sprite Tile Renders a sprite tiled in a grid
Text 2D Generates text in 2D
Texture Atlas Generates a texture atlas (sprite sheet) from individual sprites
Transparency in 2D Demonstrates transparency in 2d

3D Rendering

Example Description
3D Bloom Illustrates bloom configuration using HDR and emissive materials
3D Scene Simple 3D scene with basic shapes and lighting
3D Shapes A scene showcasing the built-in 3D shapes
3D Viewport To World Demonstrates how to use the Camera::viewport_to_world method
Animated Material Shows how to animate material properties
Anisotropy Displays an example model with anisotropy
Anti-aliasing Compares different anti-aliasing methods
Atmospheric Fog A scene showcasing the atmospheric fog effect
Auto Exposure A scene showcasing auto exposure
Blend Modes Showcases different blend modes
Built-in postprocessing Demonstrates the built-in postprocessing features
Camera sub view Demonstrates using different sub view effects on a camera
Clearcoat Demonstrates the clearcoat PBR feature
Color grading Demonstrates color grading
Deferred Rendering Renders meshes with both forward and deferred pipelines
Depth of field Demonstrates depth of field
Fog A scene showcasing the distance fog effect
Fog volumes Demonstrates fog volumes
Generate Custom Mesh Simple showcase of how to generate a custom mesh with a custom texture
Irradiance Volumes Demonstrates irradiance volumes
Lighting Illustrates various lighting options in a simple scene
Lightmaps Rendering a scene with baked lightmaps
Lines Create a custom material to draw 3d lines
Load glTF Loads and renders a glTF file as a scene
Load glTF extras Loads and renders a glTF file as a scene, including the gltf extras
Mesh Ray Cast Demonstrates ray casting with the MeshRayCast system parameter
Meshlet Meshlet rendering for dense high-poly scenes (experimental)
Motion Blur Demonstrates per-pixel motion blur
Order Independent Transparency Demonstrates how to use OIT
Orthographic View Shows how to create a 3D orthographic view (for isometric-look in games or CAD applications)
Parallax Mapping Demonstrates use of a normal map and depth map for parallax mapping
Parenting Demonstrates parent->child relationships and relative transformations
Percentage-closer soft shadows Demonstrates percentage-closer soft shadows (PCSS)
Physically Based Rendering Demonstrates use of Physically Based Rendering (PBR) properties
Query glTF primitives Query primitives in a glTF scene
Reflection Probes Demonstrates reflection probes
Render to Texture Shows how to render to a texture, useful for mirrors, UI, or exporting images
Rotate Environment Map Demonstrates how to rotate the skybox and the environment map simultaneously
Screen Space Ambient Occlusion A scene showcasing screen space ambient occlusion
Screen Space Reflections Demonstrates screen space reflections with water ripples
Scrolling fog Demonstrates how to create the effect of fog moving in the wind
Shadow Biases Demonstrates how shadow biases affect shadows in a 3d scene
Shadow Caster and Receiver Demonstrates how to prevent meshes from casting/receiving shadows in a 3d scene
Skybox Load a cubemap texture onto a cube like a skybox and cycle through different compressed texture formats.
Spherical Area Lights Demonstrates how point light radius values affect light behavior
Split Screen Demonstrates how to render two cameras to the same window to accomplish "split screen"
Spotlight Illustrates spot lights
Texture Shows configuration of texture materials
Tonemapping Compares tonemapping options
Transmission Showcases light transmission in the PBR material
Transparency in 3D Demonstrates transparency in 3d
Two Passes Renders two 3d passes to the same window from different perspectives
Update glTF Scene Update a scene from a glTF file, either by spawning the scene as a child of another entity, or by accessing the entities of the scene
Vertex Colors Shows the use of vertex colors
Visibility range Demonstrates visibility ranges
Volumetric fog Demonstrates volumetric fog and lighting
Wireframe Showcases wireframe rendering

Animation

Example Description
Animated Fox Plays an animation from a skinned glTF
Animated Transform Create and play an animation defined by code that operates on the Transform component
Animated UI Shows how to use animation clips to animate UI properties
Animation Events Demonstrate how to use animation events
Animation Graph Blends multiple animations together with a graph
Animation Masks Demonstrates animation masks
Color animation Demonstrates how to animate colors using mixing and splines in different color spaces
Custom Skinned Mesh Skinned mesh example with mesh and joints data defined in code
Eased Motion Demonstrates the application of easing curves to animate an object
Easing Functions Showcases the built-in easing functions
Morph Targets Plays an animation from a glTF file with meshes with morph targets
glTF Skinned Mesh Skinned mesh example with mesh and joints data loaded from a glTF file

Application

Example Description
Advanced log layers Illustrate how to transfer data between log layers and Bevy's ECS
Custom Loop Demonstrates how to create a custom runner (to update an app manually)
Drag and Drop An example that shows how to handle drag and drop in an app
Empty An empty application (does nothing)
Empty with Defaults An empty application with default plugins
Headless An application that runs without default plugins
Headless Renderer An application that runs with no window, but renders into image file
Log layers Illustrate how to add custom log layers
Logs Illustrate how to use generate log output
No Renderer An application that runs with default plugins and displays an empty window, but without an actual renderer
Plugin Demonstrates the creation and registration of a custom plugin
Plugin Group Demonstrates the creation and registration of a custom plugin group
Return after Run Show how to return to main after the Bevy app has exited
Thread Pool Resources Creates and customizes the internal thread pool
Without Winit Create an application without winit (runs single time, no event loop)

Assets

Example Description
Alter Mesh Shows how to modify the underlying asset of a Mesh after spawning.
Alter Sprite Shows how to modify texture assets after spawning.
Asset Decompression Demonstrates loading a compressed asset
Asset Loading Demonstrates various methods to load assets
Asset Processing Demonstrates how to process and load custom assets
Asset Settings Demonstrates various methods of applying settings when loading an asset
Custom Asset Implements a custom asset loader
Custom Asset IO Implements a custom AssetReader
Embedded Asset Embed an asset in the application binary and load it
Extra asset source Load an asset from a non-standard asset source
Hot Reloading of Assets Demonstrates automatic reloading of assets when modified on disk
Mult-asset synchronization Demonstrates how to wait for multiple assets to be loaded.
Repeated texture configuration How to configure the texture to repeat instead of the default clamp to edges

Async Tasks

Example Description
Async Compute How to use AsyncComputeTaskPool to complete longer running tasks
External Source of Data on an External Thread How to use an external thread to run an infinite task and communicate with a channel

Audio

Example Description
Audio Shows how to load and play an audio file
Audio Control Shows how to load and play an audio file, and control how it's played
Decodable Shows how to create and register a custom audio source by implementing the Decodable type.
Pitch Shows how to directly play a simple pitch
Soundtrack Shows how to play different soundtracks based on game state
Spatial Audio 2D Shows how to play spatial audio, and moving the emitter in 2D
Spatial Audio 3D Shows how to play spatial audio, and moving the emitter in 3D

Camera

Example Description
2D top-down camera A 2D top-down camera smoothly following player movements
Camera Orbit Shows how to orbit a static scene using pitch, yaw, and roll.
First person view model A first-person camera that uses a world model and a view model with different field of views (FOV)
Projection Zoom Shows how to zoom orthographic and perspective projection cameras.
Screen Shake A simple 2D screen shake effect

Dev tools

Example Description
FPS overlay Demonstrates FPS overlay

Diagnostics

Example Description
Custom Diagnostic Shows how to create a custom diagnostic
Enabling/disabling diagnostic Shows how to disable/re-enable a Diagnostic during runtime
Log Diagnostics Add a plugin that logs diagnostics, like frames per second (FPS), to the console

ECS (Entity Component System)

Example Description
Change Detection Change detection on components and resources
Component Hooks Define component hooks to manage component lifecycle events
Custom Query Parameters Groups commonly used compound queries and query filters into a single type
Custom Schedule Demonstrates how to add custom schedules
Dynamic ECS Dynamically create components, spawn entities with those components and query those components
ECS Guide Full guide to Bevy's ECS
Event Illustrates event creation, activation, and reception
Fallible System Parameters Systems are skipped if their parameters cannot be acquired
Fixed Timestep Shows how to create systems that run every fixed timestep, rather than every tick
Generic System Shows how to create systems that can be reused with different types
Hierarchy Creates a hierarchy of parents and children entities
Iter Combinations Shows how to iterate over combinations of query results
Nondeterministic System Order Systems run in parallel, but their order isn't always deterministic. Here's how to detect and fix this.
Observer Propagation Demonstrates event propagation with observers
Observers Demonstrates observers that react to events (both built-in life-cycle events and custom events)
One Shot Systems Shows how to flexibly run systems without scheduling them
Parallel Query Illustrates parallel queries with ParallelIterator
Removal Detection Query for entities that had a specific component removed earlier in the current frame
Run Conditions Run systems only when one or multiple conditions are met
Send and receive events Demonstrates how to send and receive events of the same type in a single system
Startup System Demonstrates a startup system (one that runs once when the app starts up)
System Closure Show how to use closures as systems, and how to configure Local variables by capturing external state
System Parameter Illustrates creating custom system parameters with SystemParam
System Piping Pipe the output of one system into a second, allowing you to handle any errors gracefully
System Stepping Demonstrate stepping through systems in order of execution.

Games

Example Description
Alien Cake Addict Eat the cakes. Eat them all. An example 3D game
Breakout An implementation of the classic game "Breakout".
Contributors Displays each contributor as a bouncy bevy-ball!
Desk Toy Bevy logo as a desk toy using transparent windows! Now with Googly Eyes!
Game Menu A simple game menu
Loading Screen Demonstrates how to create a loading screen that waits for all assets to be loaded and render pipelines to be compiled.

Gizmos

Example Description
2D Gizmos A scene showcasing 2D gizmos
3D Gizmos A scene showcasing 3D gizmos
Axes Demonstrates the function of axes gizmos
Light Gizmos A scene showcasing light gizmos

Input

Example Description
Char Input Events Prints out all chars as they are inputted
Gamepad Input Shows handling of gamepad input, connections, and disconnections
Gamepad Input Events Iterates and prints gamepad input and connection events
Gamepad Rumble Shows how to rumble a gamepad using force feedback
Keyboard Input Demonstrates handling a key press/release
Keyboard Input Events Prints out all keyboard events
Keyboard Modifiers Demonstrates using key modifiers (ctrl, shift)
Mouse Grab Demonstrates how to grab the mouse, locking the cursor to the app's screen
Mouse Input Demonstrates handling a mouse button press/release
Mouse Input Events Prints out all mouse events (buttons, movement, etc.)
Text Input Simple text input with IME support
Touch Input Displays touch presses, releases, and cancels
Touch Input Events Prints out all touch inputs

Math

Example Description
Cubic Splines Exhibits different modes of constructing cubic curves using splines
Custom Primitives Demonstrates how to add custom primitives and useful traits for them.
Random Sampling Demonstrates how to sample random points from mathematical primitives
Rendering Primitives Shows off rendering for all math primitives as both Meshes and Gizmos
Sampling Primitives Demonstrates all the primitives which can be sampled.
Smooth Follow Demonstrates how to make an entity smoothly follow another using interpolation

Movement

Example Description
Run physics in a fixed timestep Handles input, physics, and rendering in an industry-standard way by using a fixed timestep

Picking

Example Description
Mesh Picking Demonstrates picking meshes
Showcases simple picking events and usage Demonstrates how to use picking events to spawn simple objects
Sprite Picking Demonstrates picking sprites and sprite atlases

Reflection

Example Description
Custom Attributes Registering and accessing custom attributes on reflected types
Dynamic Types How dynamic types are used with reflection
Function Reflection Demonstrates how functions can be called dynamically using reflection
Generic Reflection Registers concrete instances of generic types that may be used with reflection
Reflection Demonstrates how reflection in Bevy provides a way to dynamically interact with Rust types
Reflection Types Illustrates the various reflection types available
Type Data Demonstrates how to create and use type data

Remote Protocol

Example Description
client A simple command line client that can control Bevy apps via the BRP
server A Bevy app that you can connect to with the BRP and edit

Scene

Example Description
Scene Demonstrates loading from and saving scenes to files

Shaders

These examples demonstrate how to implement different shaders in user code.

A shader in its most common usage is a small program that is run by the GPU per-vertex in a mesh (a vertex shader) or per-affected-screen-fragment (a fragment shader.) The GPU executes these programs in a highly parallel way.

There are also compute shaders which are used for more general processing leveraging the GPU's parallelism.

Example Description
Animated A shader that uses dynamic data like the time since startup
Array Texture A shader that shows how to reuse the core bevy PBR shading functionality in a custom material that obtains the base color from an array texture.
Compute - Game of Life A compute shader that simulates Conway's Game of Life
Custom Vertex Attribute A shader that reads a mesh's custom vertex attribute
Custom phase item Demonstrates how to enqueue custom draw commands in a render phase
Extended Material A custom shader that builds on the standard material
GPU readback A very simple compute shader that writes to a buffer that is read by the cpu
Instancing A shader that renders a mesh multiple times in one draw call using low level rendering api
Instancing Shows that multiple instances of a cube are automatically instanced in one draw call
Material A shader and a material that uses it
Material A shader and a material that uses it on a 2d mesh
Material - GLSL A shader that uses the GLSL shading language
Material - Screenspace Texture A shader that samples a texture with view-independent UV coordinates
Material Prepass A shader that uses the various textures generated by the prepass
Post Processing - Custom Render Pass A custom post processing effect, using a custom render pass that runs after the main pass
Shader Defs A shader that uses "shaders defs" (a bevy tool to selectively toggle parts of a shader)
Specialized Mesh Pipeline Demonstrates how to write a specialized mesh pipeline
Storage Buffer A shader that shows how to bind a storage buffer using a custom material.
Texture Binding Array (Bindless Textures) A shader that shows how to bind and sample multiple textures as a binding array (a.k.a. bindless textures).

State

Example Description
Computed States Advanced state patterns using Computed States.
Custom State Transition Behavior Creating and working with custom state transition schedules.
States Illustrates how to use States to control transitioning from a Menu state to an InGame state.
Sub States Using Sub States for hierarchical state handling.

Stress Tests

These examples are used to test the performance and stability of various parts of the engine in an isolated way.

Due to the focus on performance it's recommended to run the stress tests in release mode:

cargo run --release --example <example name>
Example Description
Bevymark A heavy sprite rendering workload to benchmark your system with Bevy
Many Animated Sprites Displays many animated sprites in a grid arrangement with slight offsets to their animation timers. Used for performance testing.
Many Buttons Test rendering of many UI elements
Many Cubes Simple benchmark to test per-entity draw overhead. Run with the sphere argument to test frustum culling
Many Foxes Loads an animated fox model and spawns lots of them. Good for testing skinned mesh performance. Takes an unsigned integer argument for the number of foxes to spawn. Defaults to 1000
Many Gizmos Test rendering of many gizmos
Many Glyphs Simple benchmark to test text rendering.
Many Lights Simple benchmark to test rendering many point lights. Run with WGPU_SETTINGS_PRIO=webgl2 to restrict to uniform buffers and max 256 lights
Many Sprites Displays many sprites in a grid arrangement! Used for performance testing. Use --colored to enable color tinted sprites.
Text Pipeline Text Pipeline benchmark
Transform Hierarchy Various test cases for hierarchy and transform propagation performance

Time

Example Description
Time handling Explains how Time is handled in ECS
Timers Illustrates ticking Timer resources inside systems and handling their state
Virtual time Shows how Time<Virtual> can be used to pause, resume, slow down and speed up a game.

Tools

Example Description
Gamepad Viewer Shows a visualization of gamepad buttons, sticks, and triggers
Scene Viewer A simple way to view glTF models with Bevy. Just run cargo run --release --example scene_viewer /path/to/model.gltf#Scene0, replacing the path as appropriate. With no arguments it will load the FieldHelmet glTF model from the repository assets subdirectory

Transforms

Example Description
3D Rotation Illustrates how to (constantly) rotate an object around an axis
Alignment A demonstration of Transform's axis-alignment feature
Scale Illustrates how to scale an object in each direction
Transform Shows multiple transformations of objects
Translation Illustrates how to move an object along an axis

UI (User Interface)

Example Description
Borders Demonstrates how to create a node with a border
Box Shadow Demonstrates how to create a node with a shadow
Button Illustrates creating and updating a button
CSS Grid An example for CSS Grid layout
Display and Visibility Demonstrates how Display and Visibility work in the UI.
Flex Layout Demonstrates how the AlignItems and JustifyContent properties can be composed to layout nodes and position text
Font Atlas Debug Illustrates how FontAtlases are populated (used to optimize text rendering internally)
Ghost Nodes Demonstrates the use of Ghost Nodes to skip entities in the UI layout hierarchy
Overflow Simple example demonstrating overflow behavior
Overflow Clip Margin Simple example demonstrating the OverflowClipMargin style property
Overflow and Clipping Debug An example to debug overflow and clipping behavior
Relative Cursor Position Showcases the RelativeCursorPosition component
Render UI to Texture An example of rendering UI as a part of a 3D world
Scroll Demonstrates scrolling UI containers
Size Constraints Demonstrates how the to use the size constraints to control the size of a UI node.
Text Illustrates creating and updating text
Text Debug An example for debugging text layout
Text Wrap Debug Demonstrates text wrapping
Transparency UI Demonstrates transparency for UI
UI Illustrates various features of Bevy UI
UI Material Demonstrates creating and using custom Ui materials
UI Scaling Illustrates how to scale the UI
UI Texture Atlas Illustrates how to use TextureAtlases in UI
UI Texture Atlas Slice Illustrates how to use 9 Slicing for TextureAtlases in UI
UI Texture Slice Illustrates how to use 9 Slicing in UI
UI Texture Slice Flipping and Tiling Illustrates how to flip and tile images with 9 Slicing in UI
UI Z-Index Demonstrates how to control the relative depth (z-position) of UI elements
Viewport Debug An example for debugging viewport coordinates
Window Fallthrough Illustrates how to access winit::window::Window's hittest functionality.

Window

Example Description
Clear Color Creates a solid color window
Custom User Event Handles custom user events within the event loop
Low Power Demonstrates settings to reduce power use for bevy applications
Monitor info Displays information about available monitors (displays).
Multiple Windows Demonstrates creating multiple windows, and rendering to them
Scale Factor Override Illustrates how to customize the default window settings
Screenshot Shows how to save screenshots to disk
Transparent Window Illustrates making the window transparent and hiding the window decoration
Window Drag Move Demonstrates drag move and drag resize without window decoration
Window Resizing Demonstrates resizing and responding to resizing a window
Window Settings Demonstrates customizing default window settings

Tests

Example Description
How to Test Systems How to test systems with commands, queries or resources

Platform-Specific Examples

Android

Setup

rustup target add aarch64-linux-android
cargo install cargo-ndk

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].

Alternatively, you can install Android Studio.

Build & Run

To build an Android app, you first need to build shared object files for the target architecture with cargo-ndk:

cargo ndk -t <target_name> -o <project_name>/app/src/main/jniLibs build

For example, to compile to a 64-bit ARM platform:

cargo ndk -t arm64-v8a -o android_example/app/src/main/jniLibs build

Setting the output path ensures the shared object files can be found in target-specific directories under jniLibs where the JNI can find them.

See the cargo-ndk README for other options.

After this you can build it with gradlew:

./gradlew build

Or build it with Android Studio.

Then you can test it in your Android project.

About libc++_shared.so

Bevy may require libc++_shared.so to run on Android, as it is needed by the oboe crate, but typically cargo-ndk does not copy this file automatically.

To include it, you can manually obtain it from NDK source or use a build.rs script for automation, as described in the cargo-ndk README.

Alternatively, you can modify project files to include it when building an APK. To understand the specific steps taken in this project, please refer to the comments within the project files for detailed instructions(app/CMakeList.txt, app/build.gradle, app/src/main/cpp/dummy.cpp).

Debugging

You can view the logs with the following command:

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 information.

Sometimes, running the app complains about an unknown activity. This may be fixed by uninstalling the application:

adb uninstall org.bevyengine.example

Old phones

In its examples, Bevy targets the minimum Android API that Play Store requires to upload and update apps. Users of older phones may want to use an older API when testing. By default, Bevy uses GameAvtivity, which only works for Android API level 31 and higher, so if you want to use older API, you need to switch to NativeActivity.

To use NativeActivity, you need to edit it in cargo.toml manually like this:

bevy = { version = "0.14", default-features = false, features = ["android-native-activity", ...] }

Then build it as the Build & Run section stated above.

About cargo-apk

You can also build an APK with cargo-apk, a simpler and deprecated tool which doesn't support GameActivity. If you want to use this, there is a folder inside the mobile example with instructions.

Example File Description
android mobile/src/lib.rs A 3d Scene with a button and playing sound

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
rustup target add aarch64-apple-ios x86_64-apple-ios aarch64-apple-ios-sim

Build & Run

Using bash:

cd examples/mobile
make run

In an ideal world, this will boot up, install and run the app for the first iOS simulator in your xcrun simctl list devices. If this fails, you can specify the simulator device UUID via:

DEVICE_ID=${YOUR_DEVICE_ID} make run

If you'd like to see xcode do stuff, you can run

open bevy_mobile_example.xcodeproj/

which will open xcode. You then must push the zoom zoom play button and wait for the magic.

Example File Description
ios mobile/src/lib.rs A 3d Scene with a button and playing sound

Wasm

Setup

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.

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 is used to create javascript bindings to this wasm file in the output file examples/wasm/target/wasm_example.js, which can be loaded using this example HTML file.

Then serve examples/wasm directory to browser. i.e.

# 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

WebGL2 and WebGPU

Bevy support for WebGPU is being worked on, but is currently experimental.

To build for WebGPU, you'll need to enable the webgpu feature. This will override the webgl2 feature, and builds with the webgpu feature enabled won't be able to run on browsers that don't support WebGPU.

Bevy has an helper to build its examples:

  • Build for WebGL2: cargo run -p build-wasm-example -- --api webgl2 load_gltf
  • Build for WebGPU: cargo run -p build-wasm-example -- --api webgpu load_gltf

This helper will log the command used to build the examples.

Audio in the browsers

For the moment, everything is single threaded, this can lead to stuttering when playing audio in browsers. Not all browsers react the same way for all games, you will have to experiment for your game.

In browsers, audio is not authorized to start without being triggered by an user interaction. This is to avoid multiple tabs all starting to auto play some sounds. You can find more context and explanation for this on Google Chrome blog. This page also describes a JS workaround to resume audio as soon as the user interact with your game.

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, starting with the steps described in the quick-start guide.

Now, when building the executable, use --profile wasm-release instead of --release:

cargo build --profile wasm-release --example lighting --target wasm32-unknown-unknown

To apply wasm-opt, first locate the .wasm file generated in the --out-dir of the earlier wasm-bindgen-cli command (the filename should end with _bg.wasm), then run:

wasm-opt -Oz --output optimized.wasm examples/wasm/target/lighting_bg.wasm
mv optimized.wasm examples/wasm/target/lighting_bg.wasm

Make sure your final executable size is actually smaller. Some optimizations may not be worth keeping due to compilation time increases.

For a small project with a basic 3d model and two lights, the generated file sizes are, as of July 2022, as follows:

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

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.