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https://github.com/bevyengine/bevy
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01aedc8431
# Objective Now that we can consolidate Bundles and Components under a single insert (thanks to #2975 and #6039), almost 100% of world spawns now look like `world.spawn().insert((Some, Tuple, Here))`. Spawning an entity without any components is an extremely uncommon pattern, so it makes sense to give spawn the "first class" ergonomic api. This consolidated api should be made consistent across all spawn apis (such as World and Commands). ## Solution All `spawn` apis (`World::spawn`, `Commands:;spawn`, `ChildBuilder::spawn`, and `WorldChildBuilder::spawn`) now accept a bundle as input: ```rust // before: commands .spawn() .insert((A, B, C)); world .spawn() .insert((A, B, C); // after commands.spawn((A, B, C)); world.spawn((A, B, C)); ``` All existing instances of `spawn_bundle` have been deprecated in favor of the new `spawn` api. A new `spawn_empty` has been added, replacing the old `spawn` api. By allowing `world.spawn(some_bundle)` to replace `world.spawn().insert(some_bundle)`, this opened the door to removing the initial entity allocation in the "empty" archetype / table done in `spawn()` (and subsequent move to the actual archetype in `.insert(some_bundle)`). This improves spawn performance by over 10%:  To take this measurement, I added a new `world_spawn` benchmark. Unfortunately, optimizing `Commands::spawn` is slightly less trivial, as Commands expose the Entity id of spawned entities prior to actually spawning. Doing the optimization would (naively) require assurances that the `spawn(some_bundle)` command is applied before all other commands involving the entity (which would not necessarily be true, if memory serves). Optimizing `Commands::spawn` this way does feel possible, but it will require careful thought (and maybe some additional checks), which deserves its own PR. For now, it has the same performance characteristics of the current `Commands::spawn_bundle` on main. **Note that 99% of this PR is simple renames and refactors. The only code that needs careful scrutiny is the new `World::spawn()` impl, which is relatively straightforward, but it has some new unsafe code (which re-uses battle tested BundlerSpawner code path).** --- ## Changelog - All `spawn` apis (`World::spawn`, `Commands:;spawn`, `ChildBuilder::spawn`, and `WorldChildBuilder::spawn`) now accept a bundle as input - All instances of `spawn_bundle` have been deprecated in favor of the new `spawn` api - World and Commands now have `spawn_empty()`, which is equivalent to the old `spawn()` behavior. ## Migration Guide ```rust // Old (0.8): commands .spawn() .insert_bundle((A, B, C)); // New (0.9) commands.spawn((A, B, C)); // Old (0.8): commands.spawn_bundle((A, B, C)); // New (0.9) commands.spawn((A, B, C)); // Old (0.8): let entity = commands.spawn().id(); // New (0.9) let entity = commands.spawn_empty().id(); // Old (0.8) let entity = world.spawn().id(); // New (0.9) let entity = world.spawn_empty(); ```
95 lines
3.6 KiB
Rust
95 lines
3.6 KiB
Rust
//! Demonstrates how to use transparency in 3D.
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//! Shows the effects of different blend modes.
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//! The `fade_transparency` system smoothly changes the transparency over time.
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use bevy::prelude::*;
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fn main() {
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App::new()
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.insert_resource(Msaa { samples: 4 })
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup)
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.add_system(fade_transparency)
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.run();
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}
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fn setup(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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) {
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// opaque plane, uses `alpha_mode: Opaque` by default
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commands.spawn(PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Plane { size: 6.0 })),
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material: materials.add(Color::rgb(0.3, 0.5, 0.3).into()),
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..default()
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});
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// transparent sphere, uses `alpha_mode: Mask(f32)`
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commands.spawn(PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Icosphere {
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radius: 0.5,
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subdivisions: 3,
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})),
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material: materials.add(StandardMaterial {
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// Alpha channel of the color controls transparency.
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// We set it to 0.0 here, because it will be changed over time in the
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// `fade_transparency` function.
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// Note that the transparency has no effect on the objects shadow.
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base_color: Color::rgba(0.2, 0.7, 0.1, 0.0),
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// Mask sets a cutoff for transparency. Alpha values below are fully transparent,
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// alpha values above are fully opaque.
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alpha_mode: AlphaMode::Mask(0.5),
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..default()
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}),
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transform: Transform::from_xyz(1.0, 0.5, -1.5),
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..default()
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});
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// transparent cube, uses `alpha_mode: Blend`
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commands.spawn(PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
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// Notice how there is no need to set the `alpha_mode` explicitly here.
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// When converting a color to a material using `into()`, the alpha mode is
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// automatically set to `Blend` if the alpha channel is anything lower than 1.0.
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material: materials.add(Color::rgba(0.5, 0.5, 1.0, 0.0).into()),
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transform: Transform::from_xyz(0.0, 0.5, 0.0),
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..default()
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});
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// opaque sphere
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commands.spawn(PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Icosphere {
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radius: 0.5,
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subdivisions: 3,
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})),
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material: materials.add(Color::rgb(0.7, 0.2, 0.1).into()),
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transform: Transform::from_xyz(0.0, 0.5, -1.5),
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..default()
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});
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// light
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commands.spawn(PointLightBundle {
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point_light: PointLight {
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intensity: 1500.0,
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shadows_enabled: true,
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..default()
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},
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transform: Transform::from_xyz(4.0, 8.0, 4.0),
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..default()
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});
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// camera
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commands.spawn(Camera3dBundle {
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transform: Transform::from_xyz(-2.0, 3.0, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
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..default()
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});
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}
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/// Fades the alpha channel of all materials between 0 and 1 over time.
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/// Each blend mode responds differently to this:
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/// - `Opaque`: Ignores alpha channel altogether, these materials stay completely opaque.
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/// - `Mask(f32)`: Object appears when the alpha value goes above the mask's threshold, disappears
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/// when the alpha value goes back below the threshold.
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/// - `Blend`: Object fades in and out smoothly.
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pub fn fade_transparency(time: Res<Time>, mut materials: ResMut<Assets<StandardMaterial>>) {
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let alpha = (time.time_since_startup().as_secs_f32().sin() / 2.0) + 0.5;
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for (_, material) in materials.iter_mut() {
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material.base_color.set_a(alpha);
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}
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}
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