scrolling_fog/
scrolling_fog.rs

1//! Showcases a `FogVolume`'s density texture being scrolled over time to create
2//! the effect of fog moving in the wind.
3//!
4//! The density texture is a repeating 3d noise texture and the `density_texture_offset`
5//! is moved every frame to achieve this.
6//!
7//! The example also utilizes the jitter option of `VolumetricFog` in tandem
8//! with temporal anti-aliasing to improve the visual quality of the effect.
9//!
10//! The camera is looking at a pillar with the sun peaking behind it. The light
11//! interactions change based on the density of the fog.
12
13use bevy::{
14    anti_alias::taa::TemporalAntiAliasing,
15    image::{
16        ImageAddressMode, ImageFilterMode, ImageLoaderSettings, ImageSampler,
17        ImageSamplerDescriptor,
18    },
19    light::{DirectionalLightShadowMap, FogVolume, VolumetricFog, VolumetricLight},
20    post_process::bloom::Bloom,
21    prelude::*,
22};
23
24/// Initializes the example.
25fn main() {
26    App::new()
27        .add_plugins(DefaultPlugins.set(WindowPlugin {
28            primary_window: Some(Window {
29                title: "Bevy Scrolling Fog".into(),
30                ..default()
31            }),
32            ..default()
33        }))
34        .insert_resource(DirectionalLightShadowMap { size: 4096 })
35        .add_systems(Startup, setup)
36        .add_systems(Update, scroll_fog)
37        .run();
38}
39
40/// Spawns all entities into the scene.
41fn setup(
42    mut commands: Commands,
43    mut meshes: ResMut<Assets<Mesh>>,
44    mut materials: ResMut<Assets<StandardMaterial>>,
45    assets: Res<AssetServer>,
46) {
47    // Spawn camera with temporal anti-aliasing and a VolumetricFog configuration.
48    commands.spawn((
49        Camera3d::default(),
50        Transform::from_xyz(0.0, 2.0, 0.0).looking_at(Vec3::new(-5.0, 3.5, -6.0), Vec3::Y),
51        Msaa::Off,
52        TemporalAntiAliasing::default(),
53        Bloom::default(),
54        VolumetricFog {
55            ambient_intensity: 0.0,
56            jitter: 0.5,
57            ..default()
58        },
59    ));
60
61    // Spawn a directional light shining at the camera with the VolumetricLight component.
62    commands.spawn((
63        DirectionalLight {
64            shadow_maps_enabled: true,
65            ..default()
66        },
67        Transform::from_xyz(-5.0, 5.0, -7.0).looking_at(Vec3::new(0.0, 0.0, 0.0), Vec3::Y),
68        VolumetricLight,
69    ));
70
71    // Spawn ground mesh.
72    commands.spawn((
73        Mesh3d(meshes.add(Cuboid::new(64.0, 1.0, 64.0))),
74        MeshMaterial3d(materials.add(StandardMaterial {
75            base_color: Color::BLACK,
76            perceptual_roughness: 1.0,
77            ..default()
78        })),
79        Transform::from_xyz(0.0, -0.5, 0.0),
80    ));
81
82    // Spawn pillar standing between the camera and the sun.
83    commands.spawn((
84        Mesh3d(meshes.add(Cuboid::new(2.0, 9.0, 2.0))),
85        MeshMaterial3d(materials.add(Color::BLACK)),
86        Transform::from_xyz(-10.0, 4.5, -11.0),
87    ));
88
89    // Load a repeating 3d noise texture. Make sure to set ImageAddressMode to Repeat
90    // so that the texture wraps around as the density texture offset is moved along.
91    // Also set ImageFilterMode to Linear so that the fog isn't pixelated.
92    let noise_texture = assets
93        .load_builder()
94        .with_settings(|settings: &mut _| {
95            *settings = ImageLoaderSettings {
96                sampler: ImageSampler::Descriptor(ImageSamplerDescriptor {
97                    address_mode_u: ImageAddressMode::Repeat,
98                    address_mode_v: ImageAddressMode::Repeat,
99                    address_mode_w: ImageAddressMode::Repeat,
100                    mag_filter: ImageFilterMode::Linear,
101                    min_filter: ImageFilterMode::Linear,
102                    mipmap_filter: ImageFilterMode::Linear,
103                    ..default()
104                }),
105                ..default()
106            }
107        })
108        .load("volumes/fog_noise.ktx2");
109
110    // Spawn a FogVolume and use the repeating noise texture as its density texture.
111    commands.spawn((
112        Transform::from_xyz(0.0, 32.0, 0.0).with_scale(Vec3::splat(64.0)),
113        FogVolume {
114            density_texture: Some(noise_texture),
115            density_factor: 0.05,
116            ..default()
117        },
118    ));
119}
120
121/// Moves fog density texture offset every frame.
122fn scroll_fog(time: Res<Time>, mut query: Query<&mut FogVolume>) {
123    for mut fog_volume in query.iter_mut() {
124        fog_volume.density_texture_offset += Vec3::new(0.0, 0.0, 0.04) * time.delta_secs();
125    }
126}
scrolling_fog/scrolling_fog.rs

scrolling_fog/
scrolling_fog.rs
