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volumetric_fog.rs
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volumetric_fog.rs
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//! Demonstrates volumetric fog and lighting (light shafts or god rays).
use bevy::{
color::palettes::css::RED,
core_pipeline::{bloom::Bloom, tonemapping::Tonemapping, Skybox},
math::vec3,
pbr::{FogVolume, VolumetricFog, VolumetricLight},
prelude::*,
};
const DIRECTIONAL_LIGHT_MOVEMENT_SPEED: f32 = 0.02;
/// The current settings that the user has chosen.
#[derive(Resource)]
struct AppSettings {
/// Whether volumetric spot light is on.
volumetric_spotlight: bool,
/// Whether volumetric point light is on.
volumetric_pointlight: bool,
}
impl Default for AppSettings {
fn default() -> Self {
Self {
volumetric_spotlight: true,
volumetric_pointlight: true,
}
}
}
// Define a struct to store parameters for the point light's movement.
#[derive(Component)]
struct MoveBackAndForthHorizontally {
min_x: f32,
max_x: f32,
speed: f32,
}
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.insert_resource(ClearColor(Color::Srgba(Srgba {
red: 0.02,
green: 0.02,
blue: 0.02,
alpha: 1.0,
})))
.insert_resource(AmbientLight::NONE)
.init_resource::<AppSettings>()
.add_systems(Startup, setup)
.add_systems(Update, tweak_scene)
.add_systems(Update, (move_directional_light, move_point_light))
.add_systems(Update, adjust_app_settings)
.run();
}
/// Initializes the scene.
fn setup(mut commands: Commands, asset_server: Res<AssetServer>, app_settings: Res<AppSettings>) {
// Spawn the glTF scene.
commands.spawn(SceneRoot(asset_server.load(
GltfAssetLabel::Scene(0).from_asset("models/VolumetricFogExample/VolumetricFogExample.glb"),
)));
// Spawn the camera.
commands
.spawn((
Camera3d::default(),
Camera {
hdr: true,
..default()
},
Transform::from_xyz(-1.7, 1.5, 4.5).looking_at(vec3(-1.5, 1.7, 3.5), Vec3::Y),
Tonemapping::TonyMcMapface,
Bloom::default(),
))
.insert(Skybox {
image: asset_server.load("environment_maps/pisa_specular_rgb9e5_zstd.ktx2"),
brightness: 1000.0,
..default()
})
.insert(VolumetricFog {
// This value is explicitly set to 0 since we have no environment map light
ambient_intensity: 0.0,
..default()
});
// Add the point light
commands.spawn((
Transform::from_xyz(-0.4, 1.9, 1.0),
PointLight {
shadows_enabled: true,
range: 150.0,
color: RED.into(),
intensity: 1000.0,
..default()
},
VolumetricLight,
MoveBackAndForthHorizontally {
min_x: -1.93,
max_x: -0.4,
speed: -0.2,
},
));
// Add the spot light
commands.spawn((
Transform::from_xyz(-1.8, 3.9, -2.7).looking_at(Vec3::ZERO, Vec3::Y),
SpotLight {
intensity: 5000.0, // lumens
color: Color::WHITE,
shadows_enabled: true,
inner_angle: 0.76,
outer_angle: 0.94,
..default()
},
VolumetricLight,
));
// Add the fog volume.
commands.spawn((
FogVolume::default(),
Transform::from_scale(Vec3::splat(35.0)),
));
// Add the help text.
commands.spawn((
create_text(&app_settings),
Node {
position_type: PositionType::Absolute,
top: Val::Px(12.0),
left: Val::Px(12.0),
..default()
},
));
}
fn create_text(app_settings: &AppSettings) -> Text {
format!(
"{}\n{}\n{}",
"Press WASD or the arrow keys to change the direction of the directional light",
if app_settings.volumetric_pointlight {
"Press P to turn volumetric point light off"
} else {
"Press P to turn volumetric point light on"
},
if app_settings.volumetric_spotlight {
"Press L to turn volumetric spot light off"
} else {
"Press L to turn volumetric spot light on"
}
)
.into()
}
/// A system that makes directional lights in the glTF scene into volumetric
/// lights with shadows.
fn tweak_scene(
mut commands: Commands,
mut lights: Query<(Entity, &mut DirectionalLight), Changed<DirectionalLight>>,
) {
for (light, mut directional_light) in lights.iter_mut() {
// Shadows are needed for volumetric lights to work.
directional_light.shadows_enabled = true;
commands.entity(light).insert(VolumetricLight);
}
}
/// Processes user requests to move the directional light.
fn move_directional_light(
input: Res<ButtonInput<KeyCode>>,
mut directional_lights: Query<&mut Transform, With<DirectionalLight>>,
) {
let mut delta_theta = Vec2::ZERO;
if input.pressed(KeyCode::KeyW) || input.pressed(KeyCode::ArrowUp) {
delta_theta.y += DIRECTIONAL_LIGHT_MOVEMENT_SPEED;
}
if input.pressed(KeyCode::KeyS) || input.pressed(KeyCode::ArrowDown) {
delta_theta.y -= DIRECTIONAL_LIGHT_MOVEMENT_SPEED;
}
if input.pressed(KeyCode::KeyA) || input.pressed(KeyCode::ArrowLeft) {
delta_theta.x += DIRECTIONAL_LIGHT_MOVEMENT_SPEED;
}
if input.pressed(KeyCode::KeyD) || input.pressed(KeyCode::ArrowRight) {
delta_theta.x -= DIRECTIONAL_LIGHT_MOVEMENT_SPEED;
}
if delta_theta == Vec2::ZERO {
return;
}
let delta_quat = Quat::from_euler(EulerRot::XZY, delta_theta.y, 0.0, delta_theta.x);
for mut transform in directional_lights.iter_mut() {
transform.rotate(delta_quat);
}
}
// Toggle point light movement between left and right.
fn move_point_light(
timer: Res<Time>,
mut objects: Query<(&mut Transform, &mut MoveBackAndForthHorizontally)>,
) {
for (mut transform, mut move_data) in objects.iter_mut() {
let mut translation = transform.translation;
let mut need_toggle = false;
translation.x += move_data.speed * timer.delta_secs();
if translation.x > move_data.max_x {
translation.x = move_data.max_x;
need_toggle = true;
} else if translation.x < move_data.min_x {
translation.x = move_data.min_x;
need_toggle = true;
}
if need_toggle {
move_data.speed = -move_data.speed;
}
transform.translation = translation;
}
}
// Adjusts app settings per user input.
fn adjust_app_settings(
mut commands: Commands,
keyboard_input: Res<ButtonInput<KeyCode>>,
mut app_settings: ResMut<AppSettings>,
mut point_lights: Query<Entity, With<PointLight>>,
mut spot_lights: Query<Entity, With<SpotLight>>,
mut text: Query<&mut Text>,
) {
// If there are no changes, we're going to bail for efficiency. Record that
// here.
let mut any_changes = false;
// If the user pressed P, toggle volumetric state of the point light.
if keyboard_input.just_pressed(KeyCode::KeyP) {
app_settings.volumetric_pointlight = !app_settings.volumetric_pointlight;
any_changes = true;
}
// If the user pressed L, toggle volumetric state of the spot light.
if keyboard_input.just_pressed(KeyCode::KeyL) {
app_settings.volumetric_spotlight = !app_settings.volumetric_spotlight;
any_changes = true;
}
// If there were no changes, bail out.
if !any_changes {
return;
}
// Update volumetric settings.
for point_light in point_lights.iter_mut() {
if app_settings.volumetric_pointlight {
commands.entity(point_light).insert(VolumetricLight);
} else {
commands.entity(point_light).remove::<VolumetricLight>();
}
}
for spot_light in spot_lights.iter_mut() {
if app_settings.volumetric_spotlight {
commands.entity(spot_light).insert(VolumetricLight);
} else {
commands.entity(spot_light).remove::<VolumetricLight>();
}
}
// Update the help text.
for mut text in text.iter_mut() {
*text = create_text(&app_settings);
}
}