moonlight.md

Moonlight

We can use fog to make special light, such as moonlight or sunlight.

To create moonlight, we use FogFalloff::Atmospheric in FogSettings.

commands.spawn((
    Camera3dBundle::default(),
    FogSettings {
        color: Color::rgb(0.25, 0.25, 0.25),
        falloff: FogFalloff::from_visibility_color(3., Color::BLUE),
        ..default()
    },
));

To construct FogFalloff::Atmospheric, we can use FogFalloff::from_visibility_color, which takes a visibility and a color as its two parameters. The visibility parameter is a distance from the camera where objects in the range remain their materials. The color parameter is the color of the moonlight.

The color of FogSettings controls how strong the moonlight is. We use a lower brightness in the example to create a weaker moonlight.

The full code is as follows:

use bevy::{
    app::{App, Startup},
    asset::Assets,
    core_pipeline::core_3d::Camera3dBundle,
    ecs::system::{Commands, ResMut},
    math::Vec3,
    pbr::{
        DirectionalLight, DirectionalLightBundle, FogFalloff, FogSettings, NotShadowCaster,
        PbrBundle, StandardMaterial,
    },
    render::{
        color::Color,
        mesh::{
            shape::{Plane, UVSphere},
            Mesh,
        },
    },
    transform::components::Transform,
    utils::default,
    DefaultPlugins,
};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(2., 1., 2.).looking_at(Vec3::new(0., 0.5, 0.), Vec3::Y),
            ..default()
        },
        FogSettings {
            color: Color::rgb(0.25, 0.25, 0.25),
            falloff: FogFalloff::from_visibility_color(3., Color::BLUE),
            ..default()
        },
    ));

    // left
    commands.spawn(PbrBundle {
        mesh: meshes.add(
            UVSphere {
                radius: 0.5,
                ..default()
            }
            .into(),
        ),
        material: materials.add(StandardMaterial {
            base_color: Color::RED,
            ..default()
        }),
        transform: Transform::from_xyz(-1.25, 0.5, 0.),
        ..default()
    });

    // middle
    commands.spawn(PbrBundle {
        mesh: meshes.add(
            UVSphere {
                radius: 0.5,
                ..default()
            }
            .into(),
        ),
        material: materials.add(StandardMaterial {
            base_color: Color::GREEN,
            ..default()
        }),
        transform: Transform::from_xyz(0., 0.5, 0.),
        ..default()
    });

    // right
    commands.spawn(PbrBundle {
        mesh: meshes.add(
            UVSphere {
                radius: 0.5,
                ..default()
            }
            .into(),
        ),
        material: materials.add(StandardMaterial {
            base_color: Color::BLUE,
            ..default()
        }),
        transform: Transform::from_xyz(1.25, 0.5, 0.),
        ..default()
    });

    // ground
    commands.spawn(PbrBundle {
        mesh: meshes.add(Plane::from_size(5.).into()),
        material: materials.add(StandardMaterial::default()),
        ..default()
    });

    // sky
    commands.spawn((
        PbrBundle {
            mesh: meshes.add(
                UVSphere {
                    radius: 10.,
                    ..default()
                }
                .into(),
            ),
            material: materials.add(StandardMaterial {
                cull_mode: None,
                ..default()
            }),
            ..default()
        },
        NotShadowCaster,
    ));

    // light
    commands.spawn(DirectionalLightBundle {
        directional_light: DirectionalLight {
            illuminance: 20000.,
            shadows_enabled: true,
            ..default()
        },
        transform: Transform::default().looking_to(Vec3::new(-1., -3., 0.), Vec3::Y),
        ..default()
    });
}

Result:

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