directional_light.md

Directional Light

Directional light is similar to ambient light, but with explicit direction. Surfaces that directly face to the light are brighter than surfaces with other directions.

We use DirectionalLightBundle to create a directional light.

commands.spawn(DirectionalLightBundle {
    directional_light: DirectionalLight {
        illuminance: 20000.,
        ..default()
    },
    transform: Transform::default().looking_to(Vec3::new(-1., -1., -0.1), Vec3::Y),
    ..default()
});

We use illuminance of directional_light to set the brightness of the light. The larger the brighter. See the table for valid values for illuminance.

The transform of DirectionalLightBundle sets the direction of the light. We can use the method looking_to to set the direction. In the example, we set the direction to (-1, -1, -0.1) (so the light comes from the direction (1, 1, 0.1)).

We place a Plane to indicate the x-z plane and put a Cube on it. We set our camera position to (2, 2, 3) and make it looking at the origin.

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, PbrBundle, StandardMaterial},
    render::mesh::{
        shape::{Cube, Plane},
        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., 2., 3.).looking_at(Vec3::ZERO, Vec3::Y),
        ..default()
    });

    commands.spawn(PbrBundle {
        mesh: meshes.add(Cube::new(1.).into()).into(),
        transform: Transform::from_xyz(0., 0.5, 0.),
        material: materials.add(StandardMaterial::default()).into(),
        ..default()
    });

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

    commands.spawn(DirectionalLightBundle {
        directional_light: DirectionalLight {
            illuminance: 20000.,
            ..default()
        },
        transform: Transform::default().looking_to(Vec3::new(-1., -1., -0.1), Vec3::Y),
        ..default()
    });
}

Result:

➡️ Next: Point Light

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