sunlight.md

Sunlight

For sunlight, we can use FogFalloff::from_visibility_colors together with directional_light_color and directional_light_exponent in FogSettings.

commands.spawn((
    Camera3dBundle::default(),
    FogSettings {
        color: Color::rgb(0.5, 0.5, 0.5),
        falloff: FogFalloff::from_visibility_colors(10., Color::BLUE, Color::WHITE),
        directional_light_color: Color::WHITE,
        directional_light_exponent: 50.,
        ..default()
    },
));

The from_visibility_colors takes visibility, extinction_color and inscattering_color as its parameters. The visibility parameter is a distance from the camera where objects in the range remain their materials. The inscattering color parameter is the color of the sun. The extinction color parameter is the color when the sun goes weak.

The directional_light_color controls the brightness of the sun. The directional_light_exponent specifies the size of the sun. The larger the value, the smaller the sun.

The color of FogSettings controls the diffusion of the sun.

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(0.5, 0.5, 0.5),
            falloff: FogFalloff::from_visibility_colors(10., Color::BLUE, Color::WHITE),
            directional_light_color: Color::WHITE,
            directional_light_exponent: 50.,
            ..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(2., -0.2, 0.5), Vec3::Y),
        ..default()
    });
}

Result:

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