spot_light.md

Spot Light

Spot light starts from a point, follows a direction and creates a light of a cone shape.

We use SpotLightBundle to create a spot light.

commands.spawn(SpotLightBundle {
    transform: Transform::from_xyz(0., 2., 0.).looking_at(Vec3::new(0., -1., 0.), Vec3::Z),
    ..default()
});

In transform of SpotLightBundle, we use from_xyz and looking_at to set the start position and direction of the light respectively. In the example, the light starts from the position (0, 2, 0) and faces to the direction (0, -1, 0).

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::{PbrBundle, SpotLightBundle, 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(SpotLightBundle {
        transform: Transform::from_xyz(0., 2., 0.).looking_at(Vec3::new(0., -1., 0.), Vec3::Z),
        ..default()
    });
}

Result:

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