bevy/docs/cargo_features.md
Patrick Walton 1c765c9ae7
Add support for specular tints and maps per the KHR_materials_specular glTF extension. (#14069)
This commit allows specular highlights to be tinted with a color and for
the reflectance and color tint values to vary across a model via a pair
of maps. The implementation follows the [`KHR_materials_specular`] glTF
extension. In order to reduce the number of samplers and textures in the
default `StandardMaterial` configuration, the maps are gated behind the
`pbr_specular_textures` Cargo feature.

Specular tinting is currently unsupported in the deferred renderer,
because I didn't want to bloat the deferred G-buffers. A possible fix
for this in the future would be to make the G-buffer layout more
configurable, so that specular tints could be supported on an opt-in
basis. As an alternative, Bevy could force meshes with specular tints to
render in forward mode. Both of these solutions require some more
design, so I consider them out of scope for now.

Note that the map is a *specular* map, not a *reflectance* map. In Bevy
and Filament terms, the reflectance values in the specular map range
from [0.0, 0.5], rather than [0.0, 1.0]. This is an unfortunate
[`KHR_materials_specular`] specification requirement that stems from the
fact that glTF is specified in terms of a specular strength model, not
the reflectance model that Filament and Bevy use. A workaround, which is
noted in the `StandardMaterial` documentation, is to set the
`reflectance` value to 2.0, which spreads the specular map range from
[0.0, 1.0] as normal.

The glTF loader has been updated to parse the [`KHR_materials_specular`]
extension. Note that, unless the non-default `pbr_specular_textures` is
supplied, the maps are ignored. The `specularFactor` value is applied as
usual. Note that, as with the specular map, the glTF `specularFactor` is
twice Bevy's `reflectance` value.

This PR adds a new example, `specular_tint`, which demonstrates the
specular tint and map features. Note that this example requires the
[`KHR_materials_specular`] Cargo feature.

[`KHR_materials_specular`]:
https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_specular

## Changelog

### Added

* Specular highlights can now be tinted with the `specular_tint` field
in `StandardMaterial`.
* Specular maps are now available in `StandardMaterial`, gated behind
the `pbr_specular_textures` Cargo feature.
* The `KHR_materials_specular` glTF extension is now supported, allowing
for customization of specular reflectance and specular maps. Note that
the latter are gated behind the `pbr_specular_textures` Cargo feature.
2025-01-26 20:38:46 +00:00

7.6 KiB

Cargo Features

Bevy exposes many features to customize the engine. Enabling them add functionalities but often come at the cost of longer compilation times and extra dependencies.

Default Features

The default feature set enables most of the expected features of a game engine, like rendering in both 2D and 3D, asset loading, audio and UI. To help reduce compilation time, consider disabling default features and enabling only those you need.

feature name description
android-game-activity Android GameActivity support. Default, choose between this and android-native-activity.
android_shared_stdcxx Enable using a shared stdlib for cxx on Android
animation Enable animation support, and glTF animation loading
bevy_animation Provides animation functionality
bevy_asset Provides asset functionality
bevy_audio Provides audio functionality
bevy_color Provides shared color types and operations
bevy_core_pipeline Provides cameras and other basic render pipeline features
bevy_gilrs Adds gamepad support
bevy_gizmos Adds support for rendering gizmos
bevy_gltf glTF support
bevy_mesh_picking_backend Provides an implementation for picking meshes
bevy_pbr Adds PBR rendering
bevy_picking Provides picking functionality
bevy_render Provides rendering functionality
bevy_scene Provides scene functionality
bevy_sprite Provides sprite functionality
bevy_sprite_picking_backend Provides an implementation for picking sprites
bevy_state Enable built in global state machines
bevy_text Provides text functionality
bevy_ui A custom ECS-driven UI framework
bevy_ui_picking_backend Provides an implementation for picking UI
bevy_window Windowing layer
bevy_winit winit window and input backend
custom_cursor Enable winit custom cursor support
default_font Include a default font, containing only ASCII characters, at the cost of a 20kB binary size increase
hdr HDR image format support
ktx2 KTX2 compressed texture support
multi_threaded Enables multithreaded parallelism in the engine. Disabling it forces all engine tasks to run on a single thread.
png PNG image format support
smaa_luts Include SMAA Look Up Tables KTX2 Files
sysinfo_plugin Enables system information diagnostic plugin
tonemapping_luts Include tonemapping Look Up Tables KTX2 files. If everything is pink, you need to enable this feature or change the Tonemapping method for your Camera2d or Camera3d.
vorbis OGG/VORBIS audio format support
webgl2 Enable some limitations to be able to use WebGL2. Please refer to the WebGL2 and WebGPU section of the examples README for more information on how to run Wasm builds with WebGPU.
x11 X11 display server support
zstd For KTX2 supercompression

Optional Features

feature name description
accesskit_unix Enable AccessKit on Unix backends (currently only works with experimental screen readers and forks.)
android-native-activity Android NativeActivity support. Legacy, should be avoided for most new Android games.
asset_processor Enables the built-in asset processor for processed assets.
async-io Use async-io's implementation of block_on instead of futures-lite's implementation. This is preferred if your application uses async-io.
basis-universal Basis Universal compressed texture support
bevy_ci_testing Enable systems that allow for automated testing on CI
bevy_debug_stepping Enable stepping-based debugging of Bevy systems
bevy_dev_tools Provides a collection of developer tools
bevy_image Load and access image data. Usually added by an image format
bevy_remote Enable the Bevy Remote Protocol
bevy_ui_debug Provides a debug overlay for bevy UI
bmp BMP image format support
dds DDS compressed texture support
debug_glam_assert Enable assertions in debug builds to check the validity of parameters passed to glam
detailed_trace Enable detailed trace event logging. These trace events are expensive even when off, thus they require compile time opt-in
dynamic_linking Force dynamic linking, which improves iterative compile times
embedded_watcher Enables watching in memory asset providers for Bevy Asset hot-reloading
experimental_pbr_pcss Enable support for PCSS, at the risk of blowing past the global, per-shader sampler limit on older/lower-end GPUs
exr EXR image format support
ff Farbfeld image format support
file_watcher Enables watching the filesystem for Bevy Asset hot-reloading
flac FLAC audio format support
ghost_nodes Experimental support for nodes that are ignored for UI layouting
gif GIF image format support
glam_assert Enable assertions to check the validity of parameters passed to glam
ico ICO image format support
ios_simulator Enable support for the ios_simulator by downgrading some rendering capabilities
jpeg JPEG image format support
meshlet Enables the meshlet renderer for dense high-poly scenes (experimental)
meshlet_processor Enables processing meshes into meshlet meshes for bevy_pbr
minimp3 MP3 audio format support (through minimp3)
mp3 MP3 audio format support
pbr_anisotropy_texture Enable support for anisotropy texture in the StandardMaterial, at the risk of blowing past the global, per-shader texture limit on older/lower-end GPUs
pbr_multi_layer_material_textures Enable support for multi-layer material textures in the StandardMaterial, at the risk of blowing past the global, per-shader texture limit on older/lower-end GPUs
pbr_specular_textures Enable support for specular textures in the StandardMaterial, at the risk of blowing past the global, per-shader texture limit on older/lower-end GPUs
pbr_transmission_textures Enable support for transmission-related textures in the StandardMaterial, at the risk of blowing past the global, per-shader texture limit on older/lower-end GPUs
pnm PNM image format support, includes pam, pbm, pgm and ppm
qoi QOI image format support
reflect_functions Enable function reflection
serialize Enable serialization support through serde
shader_format_glsl Enable support for shaders in GLSL
shader_format_spirv Enable support for shaders in SPIR-V
spirv_shader_passthrough Enable passthrough loading for SPIR-V shaders (Only supported on Vulkan, shader capabilities and extensions must agree with the platform implementation)
symphonia-aac AAC audio format support (through symphonia)
symphonia-all AAC, FLAC, MP3, MP4, OGG/VORBIS, and WAV audio formats support (through symphonia)
symphonia-flac FLAC audio format support (through symphonia)
symphonia-isomp4 MP4 audio format support (through symphonia)
symphonia-vorbis OGG/VORBIS audio format support (through symphonia)
symphonia-wav WAV audio format support (through symphonia)
tga TGA image format support
tiff TIFF image format support
trace Tracing support
trace_chrome Tracing support, saving a file in Chrome Tracing format
trace_tracy Tracing support, exposing a port for Tracy
trace_tracy_memory Tracing support, with memory profiling, exposing a port for Tracy
track_location Enables source location tracking for change detection and spawning/despawning, which can assist with debugging
wav WAV audio format support
wayland Wayland display server support
webgpu Enable support for WebGPU in Wasm. When enabled, this feature will override the webgl2 feature and you won't be able to run Wasm builds with WebGL2, only with WebGPU.
webp WebP image format support
zlib For KTX2 supercompression