120 lines
4.3 KiB
Rust
120 lines
4.3 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::default())
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.add_plugins(DefaultPlugins)
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.add_systems(Startup, setup)
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.add_systems(Update, 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(shape::Plane::from_size(6.0).into()),
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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(
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Mesh::try_from(shape::Icosphere {
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radius: 0.5,
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subdivisions: 3,
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})
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.unwrap(),
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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 unlit sphere, uses `alpha_mode: Mask(f32)`
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commands.spawn(PbrBundle {
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mesh: meshes.add(
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Mesh::try_from(shape::Icosphere {
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radius: 0.5,
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subdivisions: 3,
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})
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.unwrap(),
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),
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material: materials.add(StandardMaterial {
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base_color: Color::rgba(0.2, 0.7, 0.1, 0.0),
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alpha_mode: AlphaMode::Mask(0.5),
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unlit: true,
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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(
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Mesh::try_from(shape::Icosphere {
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radius: 0.5,
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subdivisions: 3,
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})
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.unwrap(),
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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.elapsed_seconds().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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