Bevy tilemap

When to use

Load this before storing a grid of tiles. Bevy draws cells with Sprite and a TextureAtlas. The grid itself is a resource and a set of entities you own.

ECS shape

• Resource: TileGrid owns width, height, and one cell id per slot.
• Component: TileCell stores the grid coordinate on the sprite entity.
• Draw: TextureAtlasLayout::from_grid slices a sheet. Sprite::from_atlas_image picks a cell index.
• Schedule: spawn the grid in Startup. Autotile rules are a plain function over neighbor ids.

Examples

[dependencies]
bevy = "0.20"

The grid is the source of truth. Sprites are a view of it.

#[derive(Resource)]
struct TileGrid {
    width: i32,
    height: i32,
    cells: Vec<u16>,
}

impl TileGrid {
    fn index(&self, x: i32, y: i32) -> Option<usize> {
        if x < 0 || y < 0 || x >= self.width || y >= self.height {
            return None;
        }
        Some((y * self.width + x) as usize)
    }

    fn get(&self, x: i32, y: i32) -> u16 {
        self.index(x, y).map(|i| self.cells[i]).unwrap_or(0)
    }
}

#[derive(Component)]
struct TileCell {
    x: i32,
    y: i32,
}

A 4 by 4 sheet of 16-pixel tiles becomes one layout asset. Each solid cell spawns a sprite.

#[derive(Resource)]
struct TileGrid {
    width: i32,
    height: i32,
    cells: Vec<u16>,
}

impl TileGrid {
    fn get(&self, x: i32, y: i32) -> u16 {
        if x < 0 || y < 0 || x >= self.width || y >= self.height {
            return 0;
        }
        self.cells[(y * self.width + x) as usize]
    }
}

#[derive(Component)]
struct TileCell {
    x: i32,
    y: i32,
}

fn spawn_tiles(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    mut layouts: ResMut<Assets<TextureAtlasLayout>>,
    grid: Res<TileGrid>,
) {
    let layout = layouts.add(TextureAtlasLayout::from_grid(
        UVec2::splat(16),
        4,
        4,
        None,
        None,
    ));
    let image = asset_server.load("tiles.png");
    let tile = 16.0;
    for y in 0..grid.height {
        for x in 0..grid.width {
            let id = grid.get(x, y);
            if id == 0 {
                continue;
            }
            commands.spawn((
                Sprite::from_atlas_image(
                    image.clone(),
                    TextureAtlas {
                        layout: layout.clone(),
                        index: id as usize,
                    },
                ),
                Transform::from_xyz(x as f32 * tile, y as f32 * tile, 0.0),
                TileCell { x, y },
            ));
        }
    }
    commands.spawn(Camera2d);
}

Four-neighbor bits pick an atlas index. Empty neighbors stay zero.

#[derive(Resource)]
struct TileGrid {
    width: i32,
    height: i32,
    cells: Vec<u16>,
}

impl TileGrid {
    fn get(&self, x: i32, y: i32) -> u16 {
        if x < 0 || y < 0 || x >= self.width || y >= self.height {
            return 0;
        }
        self.cells[(y * self.width + x) as usize]
    }
}

#[derive(Component)]
struct TileCell {
    x: i32,
    y: i32,
}

fn autotile_index(grid: &TileGrid, x: i32, y: i32) -> usize {
    let solid = |nx: i32, ny: i32| u16::from(grid.get(nx, ny) != 0);
    let mask = solid(x, y + 1)
        | (solid(x + 1, y) << 1)
        | (solid(x, y - 1) << 2)
        | (solid(x - 1, y) << 3);
    mask as usize
}

fn repaint(grid: Res<TileGrid>, mut tiles: Query<(&TileCell, &mut Sprite)>) {
    for (cell, mut sprite) in &mut tiles {
        if let Some(atlas) = sprite.texture_atlas.as_mut() {
            atlas.index = autotile_index(&grid, cell.x, cell.y);
        }
    }
}

Same job, Bevy types

Design	Bevy idiom
TileSet atlas	TextureAtlasLayout::from_grid plus Sprite::from_atlas_image
TileMap layer	TileGrid resource and one entity per visible cell
Autotile	A function from neighbor ids to an atlas index

Scope

There is no engine tilemap type. Collision from the grid is a physics concern on bevy-physics-2d. Streaming a larger world means spawning and despawning TileCell entities from the same resource.

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 TileMap or TileSet types. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No named tilemap crate as the chosen solution. 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. Cells draw with Sprite and TextureAtlas. There is no engine tile-map type.

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-procedural-generation - Seeded layouts.
• bevy-data-resources - Map resource.

Complements

• godot-tilemap-mastery - Equivalent Godot skill.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.