Bevy 3d Lighting Agent Skill

Bevy 3D lighting

When to use

Load this when a 3D scene needs lights. Materials stay on bevy-3d-materials. Spawn light entities; clustering and shadow extraction stay engine-owned.

ECS shape

• Module: bevy::light says it provides directional, point, and spot lights, plus light probes, atmosphere, volumetrics, and shadow configuration.
• Feature: bevy_light is described the same way on the crate feature list.
• PBR page names: DirectionalLightViewEntities, ExtractedDirectionalLight, ExtractedPointLight, ExtractedRectLight, GpuClusteredLight (point, spot, or rectangle), DistanceFog, LightProbePlugin, ContactShadows.
• Systems: light clustering and extraction are engine-owned. Gameplay only spawns light entities.

Light choice

| Need | Spawn |

| --- | --- |

| Sun | DirectionalLight plus CascadeShadowConfig on one entity. |

| Local omni | PointLight (intensity in lumens, range in meters). |

| Cone | SpotLight with inner_angle and outer_angle in radians. |

| Distance haze | DistanceFog on the camera entity. |

| Local image-based lighting | LightProbe with EnvironmentMapLight cubemap handles. |

bevy_solari is the experimental raytraced-lighting Cargo feature. These examples use the raster lights in bevy::light.

[dependencies]
bevy = "0.20"

use bevy::light::{
    CascadeShadowConfig, CascadeShadowConfigBuilder, DirectionalLightShadowMap, SunDisk,
};

fn spawn_sun(mut commands: Commands) {
    commands.insert_resource(DirectionalLightShadowMap { size: 4096 });
    let cascades: CascadeShadowConfig = CascadeShadowConfigBuilder {
        num_cascades: 4,
        minimum_distance: 0.1,
        first_cascade_far_bound: 10.0,
        maximum_distance: 500.0,
        overlap_proportion: 0.2,
    }
    .into();
    commands.spawn((
        DirectionalLight {
            illuminance: 10_000.0,
            shadow_maps_enabled: true,
            shadow_depth_bias: DirectionalLight::DEFAULT_SHADOW_DEPTH_BIAS,
            shadow_normal_bias: DirectionalLight::DEFAULT_SHADOW_NORMAL_BIAS,
            color: Color::srgb(1.0, 0.96, 0.9),
            ..default()
        },
        cascades,
        SunDisk::EARTH,
        Transform::from_rotation(Quat::from_euler(EulerRot::XYZ, -0.8, 0.4, 0.0)),
    ));
}

pub struct SunPlugin;

impl Plugin for SunPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, spawn_sun);
    }
}

fn spawn_local_lights(mut commands: Commands) {
    commands.spawn((
        PointLight {
            intensity: 800.0,
            range: 8.0,
            radius: 0.1,
            shadow_maps_enabled: false,
            color: Color::srgb(1.0, 0.65, 0.3),
            ..default()
        },
        Transform::from_xyz(2.0, 1.5, 0.0),
    ));
    commands.spawn((
        SpotLight {
            intensity: 4_000.0,
            range: 18.0,
            inner_angle: 0.2,
            outer_angle: 0.45,
            shadow_maps_enabled: true,
            color: Color::WHITE,
            ..default()
        },
        Transform::from_xyz(0.0, 2.2, 1.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));
}

fn spawn_fog_camera(mut commands: Commands) {
    commands.spawn((
        Camera3d::default(),
        DistanceFog {
            color: Color::srgb(0.65, 0.7, 0.78),
            directional_light_color: Color::srgb(1.0, 0.9, 0.7),
            directional_light_exponent: 8.0,
            falloff: FogFalloff::Linear {
                start: 20.0,
                end: 90.0,
            },
        },
        Transform::from_xyz(0.0, 2.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));
}

fn orbit_sun(time: Res<Time>, mut suns: Query<&mut Transform, With<DirectionalLight>>) {
    for mut transform in &mut suns {
        transform.rotation = Quat::from_euler(
            EulerRot::XYZ,
            -std::f32::consts::FRAC_PI_2 + time.elapsed_secs() * 0.04,
            0.35,
            0.0,
        );
    }
}

fn keep_nearest_point_shadows(
    camera: Query<&GlobalTransform, With<Camera3d>>,
    mut lights: Query<(&GlobalTransform, &mut PointLight)>,
) {
    let Ok(view) = camera.single() else {
        return;
    };
    let origin = view.translation();
    let mut ranked: Vec<(f32, Mut<PointLight>)> = lights
        .iter_mut()
        .map(|(transform, light)| (transform.translation().distance(origin), light))
        .collect();
    ranked.sort_by(|a, b| a.0.total_cmp(&b.0));
    for (index, (_, light)) in ranked.iter_mut().enumerate() {
        light.shadow_maps_enabled = index < 4;
    }
}

pub struct LightingPlugin;

impl Plugin for LightingPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, (spawn_local_lights, spawn_fog_camera))
            .add_systems(Update, (orbit_sun, keep_nearest_point_shadows).chain());
    }
}

Expert Knowledge Delta

Target: Bevy 0.20+.

Core ECS types: Component, Resource, Query, Commands, Startup, Update, Fixed / FixedMain (bevy::time), .chain(), Plugin, DefaultPlugins, MinimalPlugins. Messages and observers are an ownership slot. See bevy-events-messaging for their APIs. Systems run in parallel unless .chain() orders the ones that conflict.

Who owns state

| Piece | Owner | Who may mutate | Schedule |

| --- | --- | --- | --- |

| Data on one entity | Component | One system via Query | Update or FixedMain |

| One value for the whole app | Resource | One system | Startup to insert, then the schedule that reads it |

| Spawn | Commands | The spawning system | Startup for the initial world; later schedules for runtime spawn |

| Order that must not race | .chain() | The chained systems only | Same schedule |

| Plugin boundary | Plugin | build registers systems and resources | Before the app runs |

Borrow rule: two systems that both mutably query the same component must be ordered (.chain()) or split so only one writes. Unrelated systems stay parallel. That is the ECS page rule, not a guess at a system-set API.

Decision

| If you need | Do this | Do not |

| --- | --- | --- |

| Per-entity data | Component + Query | One script that owns the whole actor |

| App-wide config or clock | Resource | Copy the value onto every entity |

| Stable simulation step | FixedMain and the Fixed clock | Tie simulation to raw frame Update |

| Startup spawn | Commands in Startup | Spawn from a render system |

| Cross-system notice that is not shared state | Message or observer slot in bevy-events-messaging | A new event type invented in this file |

| An API outside the documented set | Check the official docs first | A made-up crate or API |

Load references/ecs-ownership.md for the ownership table.

NEVER

• Do not pin /0.20.0/ in docs URLs. WHY: links stay on latest; the 0.20 target is stated once in prose.
• Do not mutably query the same component from two unordered systems. WHY: the schedule runs systems in parallel unless .chain() orders them.
• Do not invent a physics, navigation, networking, or XR crate here. WHY: this skill only names documented Bevy crates and modules.

• No light-node types from another engine. WHY: a ported node API will not cluster, extract, or cast cascades the way bevy::light does.
• No foreign engine types in Bevy code. WHY: the schedule, queries, and light components only exist on Bevy entities.
• No invented APIs or unnamed third-party crates as the chosen solver. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

The library pin on bevy-master stays 0.20.0. Load references/ecs-ownership.md when deciding whether a light value is a component or a resource. Do not load it for material authoring.

Official Documentation

• Assets - Official asset catalog. No third-party crate was selected.
• Examples - Example tree on the latest branch.
• ECS - Component, systems, Query, Startup, Update, and .chain().
• Plugins - Plugin, DefaultPlugins, MinimalPlugins, and add_plugins.

Related Skills

Prerequisites

• bevy-master - Hub and schedules.
• bevy-ecs-composition - Components and systems.
• bevy-3d-materials - Lit surfaces.
• bevy-camera-systems - Camera the lights affect.

Complements

• bevy-3d-world-building - Place light entities in a level.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.