Bevy Shaders Agent Skill

Bevy shaders and materials

When to use

Load this when a surface needs a custom material or a full-screen effect. StandardMaterial field lists stay on bevy-3d-materials. Shader source is WGSL loaded as an asset.

ECS shape

• Shader asset: AssetServer loads a Shader from a path. ShaderRef::Handle or a path string points a material at that asset.
• Material: implement Material, derive AsBindGroup, and register MaterialPlugin::<T>. The engine extracts materials. Do not schedule a shader compiler.
• Full-screen: Bloom is a camera component from bevy::post_process. It requires an HDR camera, which the component requests itself.

Examples

[dependencies]
bevy = "0.20"

A material stores a color uniform and names its fragment shader. Register the plugin before any system spawns that material.

use bevy::pbr::{Material, MaterialPlugin};
use bevy::render::render_resource::AsBindGroup;
use bevy::shader::ShaderRef;

#[derive(Asset, TypePath, AsBindGroup, Clone)]
struct PulseMaterial {
    #[uniform(0)]
    color: LinearRgba,
}

impl Material for PulseMaterial {
    fn fragment_shader() -> ShaderRef {
        "shaders/pulse.wgsl".into()
    }
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugins(MaterialPlugin::<PulseMaterial>::default())
        .run();
}

Spawn uses the same mesh and material components as a PBR surface. The asset store owns the material.

use bevy::pbr::Material;
use bevy::render::render_resource::AsBindGroup;
use bevy::shader::ShaderRef;

#[derive(Asset, TypePath, AsBindGroup, Clone)]
struct PulseMaterial {
    #[uniform(0)]
    color: LinearRgba,
}

impl Material for PulseMaterial {
    fn fragment_shader() -> ShaderRef {
        "shaders/pulse.wgsl".into()
    }
}

fn spawn_pulse(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<PulseMaterial>>,
) {
    let mesh = meshes.add(Cuboid::new(1.0, 1.0, 1.0));
    let material = materials.add(PulseMaterial {
        color: LinearRgba::rgb(0.2, 0.7, 0.9),
    });
    commands.spawn((
        Mesh3d(mesh),
        MeshMaterial3d(material),
        Transform::default(),
    ));
}

Load the shader yourself when the handle must be explicit. ShaderRef accepts that handle.

use bevy::shader::{Shader, ShaderRef};

#[derive(Resource)]
struct PulseShader(Handle<Shader>);

fn load_pulse(asset_server: Res<AssetServer>, mut commands: Commands) {
    let handle: Handle<Shader> = asset_server.load("shaders/pulse.wgsl");
    commands.insert_resource(PulseShader(handle));
}

fn shader_ref(shader: Res<PulseShader>) -> ShaderRef {
    shader.0.clone().into()
}

Bloom is the full-screen pass. Intensity is the scene-wide scatter amount.

use bevy::post_process::bloom::Bloom;

fn spawn_bloom_camera(mut commands: Commands) {
    commands.spawn((
        Camera3d::default(),
        Bloom {
            intensity: 0.2,
            ..default()
        },
    ));
}

Same job, Bevy types

| Design | Bevy idiom |

| --- | --- |

| ShaderMaterial | Material plus a WGSL path in fragment_shader |

| Spatial shader | Vertex and fragment ShaderRef on that material |

| Full-screen pass | Bloom (or another bevy::post_process component) on the camera |

Scope

WGSL entry points live in the shader file the ShaderRef names. Bindings are the AsBindGroup fields on the material struct. Pipeline specialization stays inside the material plugin.

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 | A scene-tree script hung on the entity |

| 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 Godot shader language or hint syntax. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No Godot types in Bevy code. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.
• 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

Official pages stay on unversioned bevy.org URLs. The library pin on bevy-master stays 0.20.0. Custom surfaces use Material, AsBindGroup, and MaterialPlugin. StandardMaterial field lists stay on bevy-3d-materials.

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 - StandardMaterial surface fields.
• bevy-asset-scenes - Asset handles.

Complements

• bevy-3d-lighting - Lights are not shaders.
• godot-shaders-basics - Equivalent Godot skill.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.