fog_volumes/
fog_volumes.rs

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
8use bevy::{
9    camera::Hdr,
10    light::{FogVolume, VolumetricFog, VolumetricLight},
11    math::vec3,
12    prelude::*,
13};
14
15/// Entry point.
16fn 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.
32fn 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.
74fn 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}
fog_volumes/fog_volumes.rs

fog_volumes/
fog_volumes.rs
