docs/bevy/examples/3d/fog_volumes.rs 2.5 K · 80 lines · raw · history

1 //! Demonstrates fog volumes with voxel density textures.
2 //!
3 //! We render the Stanford bunny as a fog volume. Parts of the bunny become
4 //! lighter and darker as the camera rotates. This is physically-accurate
5 //! behavior that results from the scattering and absorption of the directional
6 //! light.
7
8 use bevy::{
9 camera::Hdr,
10 light::{FogVolume, VolumetricFog, VolumetricLight},
11 math::vec3,
12 prelude::*,
13 };
14
15 /// Entry point.
16 fn main() {
17 App::new()
18 .add_plugins(DefaultPlugins.set(WindowPlugin {
19 primary_window: Some(Window {
20 title: "Bevy Fog Volumes Example".into(),
21 ..default()
22 }),
23 ..default()
24 }))
25 .insert_resource(GlobalAmbientLight::NONE)
26 .add_systems(Startup, setup)
27 .add_systems(Update, rotate_camera)
28 .run();
29 }
30
31 /// Spawns all the objects in the scene.
32 fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
33 // Spawn a fog volume with a voxelized version of the Stanford bunny.
34 commands.spawn((
35 Transform::from_xyz(0.0, 0.5, 0.0),
36 FogVolume {
37 density_texture: Some(asset_server.load("volumes/bunny.ktx2")),
38 density_factor: 1.0,
39 // Scatter as much of the light as possible, to brighten the bunny
40 // up.
41 scattering: 1.0,
42 ..default()
43 },
44 ));
45
46 // Spawn a bright directional light that illuminates the fog well.
47 commands.spawn((
48 Transform::from_xyz(1.0, 1.0, -0.3).looking_at(vec3(0.0, 0.5, 0.0), Vec3::Y),
49 DirectionalLight {
50 shadow_maps_enabled: true,
51 illuminance: 32000.0,
52 ..default()
53 },
54 // Make sure to add this for the light to interact with the fog.
55 VolumetricLight,
56 ));
57
58 // Spawn a camera.
59 commands.spawn((
60 Camera3d::default(),
61 Transform::from_xyz(-0.75, 1.0, 2.0).looking_at(vec3(0.0, 0.0, 0.0), Vec3::Y),
62 Hdr,
63 VolumetricFog {
64 // Make this relatively high in order to increase the fog quality.
65 step_count: 64,
66 // Disable ambient light.
67 ambient_intensity: 0.0,
68 ..default()
69 },
70 ));
71 }
72
73 /// Rotates the camera a bit every frame.
74 fn rotate_camera(mut cameras: Query<&mut Transform, With<Camera3d>>) {
75 for mut camera_transform in cameras.iter_mut() {
76 *camera_transform =
77 Transform::from_translation(Quat::from_rotation_y(0.01) * camera_transform.translation)
78 .looking_at(vec3(0.0, 0.5, 0.0), Vec3::Y);
79 }
80 }