bevy/docs/cargo_features.md
Joona Aalto 0e30b68b20
Add mesh picking backend and MeshRayCast system parameter (#15800)
# Objective

Closes #15545.

`bevy_picking` supports UI and sprite picking, but not mesh picking.
Being able to pick meshes would be extremely useful for various games,
tools, and our own examples, as well as scene editors and inspectors.
So, we need a mesh picking backend!

Luckily,
[`bevy_mod_picking`](https://github.com/aevyrie/bevy_mod_picking) (which
`bevy_picking` is based on) by @aevyrie already has a [backend for
it](74f0c3c0fb/backends/bevy_picking_raycast/src/lib.rs)
using [`bevy_mod_raycast`](https://github.com/aevyrie/bevy_mod_raycast).
As a side product of adding mesh picking, we also get support for
performing ray casts on meshes!

## Solution

Upstream a large chunk of the immediate-mode ray casting functionality
from `bevy_mod_raycast`, and add a mesh picking backend based on
`bevy_mod_picking`. Huge thanks to @aevyrie who did all the hard work on
these incredible crates!

All meshes are pickable by default. Picking can be disabled for
individual entities by adding `PickingBehavior::IGNORE`, like normal.
Or, if you want mesh picking to be entirely opt-in, you can set
`MeshPickingBackendSettings::require_markers` to `true` and add a
`RayCastPickable` component to the desired camera and target entities.

You can also use the new `MeshRayCast` system parameter to cast rays
into the world manually:

```rust
fn ray_cast_system(mut ray_cast: MeshRayCast, foo_query: Query<(), With<Foo>>) {
    let ray = Ray3d::new(Vec3::ZERO, Dir3::X);

    // Only ray cast against entities with the `Foo` component.
    let filter = |entity| foo_query.contains(entity);

    // Never early-exit. Note that you can change behavior per-entity.
    let early_exit_test = |_entity| false;

    // Ignore the visibility of entities. This allows ray casting hidden entities.
    let visibility = RayCastVisibility::Any;

    let settings = RayCastSettings::default()
        .with_filter(&filter)
        .with_early_exit_test(&early_exit_test)
        .with_visibility(visibility);

    // Cast the ray with the settings, returning a list of intersections.
    let hits = ray_cast.cast_ray(ray, &settings);
}
```

This is largely a direct port, but I did make several changes to match
our APIs better, remove things we don't need or that I think are
unnecessary, and do some general improvements to code quality and
documentation.

### Changes Relative to `bevy_mod_raycast` and `bevy_mod_picking`

- Every `Raycast` and "raycast" has been renamed to `RayCast` and "ray
cast" (similar reasoning as the "Naming" section in #15724)
- `Raycast` system param has been renamed to `MeshRayCast` to avoid
naming conflicts and to be explicit that it is not for colliders
- `RaycastBackend` has been renamed to `MeshPickingBackend`
- `RayCastVisibility` variants are now `Any`, `Visible`, and
`VisibleInView` instead of `Ignore`, `MustBeVisible`, and
`MustBeVisibleAndInView`
- `NoBackfaceCulling` has been renamed to `RayCastBackfaces`, to avoid
implying that it affects the rendering of backfaces for meshes (it
doesn't)
- `SimplifiedMesh` and `RayCastBackfaces` live near other ray casting
API types, not in their own 10 LoC module
- All intersection logic and types are in the same `intersections`
module, not split across several modules
- Some intersection types have been renamed to be clearer and more
consistent
	- `IntersectionData` -> `RayMeshHit` 
	- `RayHit` -> `RayTriangleHit`
- General documentation and code quality improvements

### Removed / Not Ported

- Removed unused ray helpers and types, like `PrimitiveIntersection`
- Removed getters on intersection types, and made their properties
public
- There is no `2d` feature, and `Raycast::mesh_query` and
`Raycast::mesh2d_query` have been merged into `MeshRayCast::mesh_query`,
which handles both 2D and 3D
- I assume this existed previously because `Mesh2dHandle` used to be in
`bevy_sprite`. Now both the 2D and 3D mesh are in `bevy_render`.
- There is no `debug` feature or ray debug rendering
- There is no deferred API (`RaycastSource`)
- There is no `CursorRayPlugin` (the picking backend handles this)

### Note for Reviewers

In case it's helpful, the [first
commit](281638ef10)
here is essentially a one-to-one port. The rest of the commits are
primarily refactoring and cleaning things up in the ways listed earlier,
as well as changes to the module structure.

It may also be useful to compare the original [picking
backend](74f0c3c0fb/backends/bevy_picking_raycast/src/lib.rs)
and [`bevy_mod_raycast`](https://github.com/aevyrie/bevy_mod_raycast) to
this PR. Feel free to mention if there are any changes that I should
revert or something I should not include in this PR.

## Testing

I tested mesh picking and relevant components in some examples, for both
2D and 3D meshes, and added a new `mesh_picking` example. I also
~~stole~~ ported over the [ray-mesh intersection
benchmark](dbc5ef32fe/benches/ray_mesh_intersection.rs)
from `bevy_mod_raycast`.

---

## Showcase

Below is a version of the `2d_shapes` example modified to demonstrate 2D
mesh picking. This is not included in this PR.


https://github.com/user-attachments/assets/7742528c-8630-4c00-bacd-81576ac432bf

And below is the new `mesh_picking` example:


https://github.com/user-attachments/assets/b65c7a5a-fa3a-4c2d-8bbd-e7a2c772986e

There is also a really cool new `mesh_ray_cast` example ported over from
`bevy_mod_raycast`:


https://github.com/user-attachments/assets/3c5eb6c0-bd94-4fb0-bec6-8a85668a06c9

---------

Co-authored-by: Aevyrie <aevyrie@gmail.com>
Co-authored-by: Trent <2771466+tbillington@users.noreply.github.com>
Co-authored-by: François Mockers <mockersf@gmail.com>
2024-10-13 17:24:19 +00:00

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Markdown

<!-- MD041 - This file will be included in docs and should not start with a top header -->
<!-- markdownlint-disable-file MD041 -->
## Cargo Features
Bevy exposes many features to customise 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](https://www.khronos.org/gltf/) support|
|bevy_mesh_picking_backend|Provides an implementation for picking meshes|
|bevy_pbr|Adds PBR rendering|
|bevy_picking|Provides picking functionality|
|bevy_remote|Enable the Bevy Remote Protocol|
|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_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](https://github.com/bevyengine/bevy/tree/latest/examples#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.|
|avif|AVIF image format support|
|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|
|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|
|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|
|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_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_change_detection|Enables source location tracking for change detection, 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|