docs/bevy/examples/3d/transparency_3d.rs 4.4 K · 115 lines · raw · history

1 //! Demonstrates how to use transparency in 3D.
2 //! Shows the effects of different blend modes.
3 //! The `fade_transparency` system smoothly changes the transparency over time.
4
5 use bevy::{math::ops, prelude::*};
6
7 fn main() {
8 App::new()
9 .add_plugins(DefaultPlugins)
10 .add_systems(Startup, setup)
11 .add_systems(Update, fade_transparency)
12 .run();
13 }
14
15 fn setup(
16 mut commands: Commands,
17 mut meshes: ResMut<Assets<Mesh>>,
18 mut materials: ResMut<Assets<StandardMaterial>>,
19 ) {
20 // Opaque plane, uses `alpha_mode: Opaque` by default
21 commands.spawn((
22 Mesh3d(meshes.add(Plane3d::default().mesh().size(6.0, 6.0))),
23 MeshMaterial3d(materials.add(Color::srgb(0.3, 0.5, 0.3))),
24 ));
25
26 // Transparent sphere, uses `alpha_mode: Mask(f32)`
27 commands.spawn((
28 Mesh3d(meshes.add(Sphere::new(0.5).mesh().ico(3).unwrap())),
29 MeshMaterial3d(materials.add(StandardMaterial {
30 // Alpha channel of the color controls transparency.
31 // We set it to 0.0 here, because it will be changed over time in the
32 // `fade_transparency` function.
33 // Note that the transparency has no effect on the objects shadow.
34 base_color: Color::srgba(0.2, 0.7, 0.1, 0.0),
35 // Mask sets a cutoff for transparency. Alpha values below are fully transparent,
36 // alpha values above are fully opaque.
37 alpha_mode: AlphaMode::Mask(0.5),
38 ..default()
39 })),
40 Transform::from_xyz(1.0, 0.5, -1.5),
41 ));
42
43 // Transparent unlit sphere, uses `alpha_mode: Mask(f32)`
44 commands.spawn((
45 Mesh3d(meshes.add(Sphere::new(0.5).mesh().ico(3).unwrap())),
46 MeshMaterial3d(materials.add(StandardMaterial {
47 base_color: Color::srgba(0.2, 0.7, 0.1, 0.0),
48 alpha_mode: AlphaMode::Mask(0.1),
49 unlit: true,
50 ..default()
51 })),
52 Transform::from_xyz(-1.0, 0.5, -1.5),
53 ));
54
55 // Transparent cube, uses `alpha_mode: Blend`
56 commands.spawn((
57 Mesh3d(meshes.add(Cuboid::default())),
58 // Notice how there is no need to set the `alpha_mode` explicitly here.
59 // When converting a color to a material using `into()`, the alpha mode is
60 // automatically set to `Blend` if the alpha channel is anything lower than 1.0.
61 MeshMaterial3d(materials.add(Color::srgba(0.5, 0.5, 1.0, 0.0))),
62 Transform::from_xyz(0.0, 0.5, 0.0),
63 ));
64
65 // Transparent cube, uses `alpha_mode: AlphaToCoverage`
66 commands.spawn((
67 Mesh3d(meshes.add(Cuboid::default())),
68 MeshMaterial3d(materials.add(StandardMaterial {
69 base_color: Color::srgba(0.5, 1.0, 0.5, 0.0),
70 alpha_mode: AlphaMode::AlphaToCoverage,
71 ..default()
72 })),
73 Transform::from_xyz(-1.5, 0.5, 0.0),
74 ));
75
76 // Opaque sphere
77 commands.spawn((
78 Mesh3d(meshes.add(Sphere::new(0.5).mesh().ico(3).unwrap())),
79 MeshMaterial3d(materials.add(Color::srgb(0.7, 0.2, 0.1))),
80 Transform::from_xyz(0.0, 0.5, -1.5),
81 ));
82
83 // Light
84 commands.spawn((
85 PointLight {
86 shadow_maps_enabled: true,
87 ..default()
88 },
89 Transform::from_xyz(4.0, 8.0, 4.0),
90 ));
91
92 // Camera
93 commands.spawn((
94 Camera3d::default(),
95 Transform::from_xyz(-2.0, 3.0, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
96 ));
97 }
98
99 /// Fades the alpha channel of all materials between 0 and 1 over time.
100 /// Each blend mode responds differently to this:
101 /// - [`Opaque`](AlphaMode::Opaque): Ignores alpha channel altogether, these materials stay completely opaque.
102 /// - [`Mask(f32)`](AlphaMode::Mask): Object appears when the alpha value goes above the mask's threshold, disappears
103 /// when the alpha value goes back below the threshold.
104 /// - [`Blend`](AlphaMode::Blend): Object fades in and out smoothly.
105 /// - [`AlphaToCoverage`](AlphaMode::AlphaToCoverage): Object fades in and out
106 /// in steps corresponding to the number of multisample antialiasing (MSAA)
107 /// samples in use. For example, assuming 8xMSAA, the object will be
108 /// completely opaque, then will be 7/8 opaque (1/8 transparent), then will be
109 /// 6/8 opaque, then 5/8, etc.
110 pub fn fade_transparency(time: Res<Time>, mut materials: ResMut<Assets<StandardMaterial>>) {
111 let alpha = (ops::sin(time.elapsed_secs()) / 2.0) + 0.5;
112 for (_, material) in materials.iter_mut() {
113 material.base_color.set_alpha(alpha);
114 }
115 }