unity-tilemap-2d

Imported from gamedev-skills/awesome-gamedev-agent-skills (skills/unity/unity-tilemap-2d/SKILL.md) via skills.sh. Install upstream with npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill unity-tilemap-2d. Copyright stays with the author.

Unity 2D Tilemap

Author and script tile-based 2D levels in Unity 6.3 LTS with the Grid/Tilemap system, the Tile Palette, colliders, and runtime painting. Targets Unity 6.3 LTS (6000.3).

Package note: the core Tilemap (Grid, Tilemap, Tile, TilemapCollider2D) is built in, and so is the Tile Palette with its default brush. Rule Tiles, Animated Tiles, and the extra brushes (Random, Line, GameObject, Group) live in the separate "2D Tilemap Extras" package (com.unity.2d.tilemap.extras, 6.0.x for Unity 6.3) — install it via Package Manager before using RuleTile.

When to use

• Use when laying out a 2D level by painting tiles, setting up a Grid + Tilemap, adding collision to the map, using auto-tiling Rule Tiles, or generating/editing tiles from script.
• Use when scenes contain a Grid with Tilemap children, or *.asset tile/palette files.

When not to use: level design practice (pacing, blockout, layout principles) → level-design. 3D tile/grid placement → Unity's own 3D tooling (ProBuilder / grid brushes; no dedicated skill here). The platformer character that moves over the tiles → platformer / unity-physics.

Core workflow

1. Create the grid: GameObject → 2D Object → Tilemap → Rectangular (the Grid's Cell Layout also offers Hexagonal and Isometric for hex/iso levels). This makes a Grid with a child Tilemap (+ TilemapRenderer). Use one Tilemap per layer (background, ground, foreground) and set each renderer's sorting.
2. Open the Tile Palette (Window → 2D → Tile Palette), drag in a sliced sprite sheet to create Tile assets, then paint with the brush tools.
3. Add collision to the solid layer: TilemapCollider2D. For one merged collider (far cheaper and gap-free), also add CompositeCollider2D (+ a Rigidbody2D set to Static) and set the tilemap collider's Composite Operation to Merge.
4. Auto-tile with Rule Tiles (2D Tilemap Extras) so edges/corners pick the right sprite automatically instead of hand-placing every variant.
5. Edit at runtime via script with cell coordinates (Vector3Int): SetTile, GetTile, SetTilesBlock, converting world↔cell with the Grid/Tilemap.
6. Verify in Play mode: confirm collisions (Physics Debugger), sorting order, and that RefreshAllTiles ran after bulk edits.

Patterns

1. Painting tiles at runtime (cell coordinates)

using UnityEngine;
using UnityEngine.Tilemaps;

public class TilePainter : MonoBehaviour
{
    [SerializeField] private Tilemap tilemap;   // assign the target Tilemap
    [SerializeField] private TileBase groundTile;

    // World position -> cell, then place a tile.
    public void PaintAt(Vector3 worldPos)
    {
        Vector3Int cell = tilemap.WorldToCell(worldPos);
        tilemap.SetTile(cell, groundTile);
    }

    public bool IsSolid(Vector3 worldPos)
        => tilemap.GetTile(tilemap.WorldToCell(worldPos)) != null;
}

2. Bulk fill a region (faster than per-cell SetTile)

// SetTilesBlock writes a whole BoundsInt in one call — use it for procedural rooms/floors.
public void FillFloor(Tilemap map, TileBase tile, int width, int height)
{
    var bounds = new BoundsInt(0, 0, 0, width, height, 1);
    var tiles  = new TileBase[width * height];
    for (int i = 0; i < tiles.Length; i++) tiles[i] = tile;
    map.SetTilesBlock(bounds, tiles);
}

3. Clearing and refreshing

tilemap.SetTile(cell, null);   // null erases the tile at that cell
tilemap.RefreshTile(cell);     // re-evaluate just this cell's rule/animated neighbors (cheap)
// RefreshAllTiles() re-evaluates the ENTIRE map — reserve it for full regenerations, not per-edit.

Pitfalls

• RuleTile type not found — it's not built in. Install the 2D Tilemap Extras package (com.unity.2d.tilemap.extras) via Package Manager.
• A collider per tile tanks performance / leaves seams — add a CompositeCollider2D with a static Rigidbody2D and set Composite Operation to Merge to merge the whole layer into one smooth shape.
• No "Used By Composite" checkbox, or an obsolete warning on usedByComposite — Unity 6 replaced it with Composite Operation (Collider2D.compositeOperation). Old usedByComposite = true maps to CompositeOperation.Merge; write that instead.
• Small gaps remain between merged tiles — raise the Tilemap Collider 2D's Extrusion Factor so neighbouring tile shapes fall within the Composite Collider 2D's Vertex Distance.
• Confusing world and cell coordinates — SetTile/GetTile take a Vector3Int cell, not a world position. Always convert with WorldToCell / CellToWorld.
• Tiles render behind/in front of sprites unexpectedly — set each TilemapRenderer's Sorting Layer and Order in Layer; multiple tilemaps need explicit ordering.
• Rule/animated tiles don't update after script edits — refresh after writes, but prefer the targeted RefreshTile(cell) for a few edits; RefreshAllTiles() re-evaluates every tile on the map and stalls large levels. Reserve the full refresh for whole-map regenerations.
• Painting onto the wrong layer — the active target Tilemap in the Tile Palette determines where paint lands; check the "Active Tilemap" dropdown.

References

• Primary docs: Unity Manual "Tilemaps" (https://docs.unity3d.com/Manual/tilemaps/work-with-tilemaps/tilemap-reference.html), ScriptReference/Tilemaps.Tilemap, ScriptReference/Collider2D-compositeOperation, the Manual "Tilemap Collider 2D component reference", and the 2D Tilemap Extras package manual (https://docs.unity3d.com/Packages/com.unity.2d.tilemap.extras@6.0/manual/index.html) for Rule Tiles. (@6.0 is the version that ships with Unity 6.3 LTS; the old @1.6 docs are for Unity 2021-era projects.)

Related skills

• level-design — engine-agnostic blockout, pacing, and tile layout practice.
• procedural-gen — generating the tile data (noise, RNG, dungeons) you feed to SetTilesBlock.
• platformer / roguelike — genres that compose this skill with movement and generation.