Tilemap painting in Unity - Deep Dive

Overview - Tilemap painting

What is it?

Tilemap painting is a way to create 2D game worlds by placing small square images called tiles on a grid. It lets you build maps like floors, walls, or landscapes quickly and neatly. Instead of drawing everything by hand, you paint tiles like using a digital stamp. This helps make game levels easier to design and change.

Why it matters

Without tilemap painting, game creators would have to place each piece of the world one by one, which is slow and error-prone. Tilemaps let you build large, detailed worlds fast and keep them organized. This saves time and helps games run smoothly because the computer knows the world is made of simple, repeatable blocks.

Where it fits

Before learning tilemap painting, you should understand basic Unity concepts like scenes, sprites, and the Unity Editor interface. After mastering tilemap painting, you can learn about advanced topics like tilemap animations, procedural map generation, and optimizing tilemaps for performance.

Mental Model

Core Idea

Tilemap painting is like using a digital stamp pad to place small images on a grid, building a bigger picture one tile at a time.

Think of it like...

Imagine making a mosaic by placing small colored tiles on a board to create a picture. Each tile is simple, but together they form a detailed image. Tilemap painting works the same way for game worlds.

┌───────────────┐
│ Tile Palette  │
│ [Tile1][Tile2]│
│ [Tile3][Tile4]│
└──────┬────────┘
       │ Paint
       ▼
┌─────────────────────┐
│ Tilemap Grid        │
│ [ ][ ][ ][ ][ ]     │
│ [ ][ ][ ][ ][ ]     │
│ [ ][ ][ ][ ][ ]     │
└─────────────────────┘

Build-Up - 7 Steps

1

Foundation

Understanding Tiles and Sprites

Concept: Learn what tiles and sprites are and how they represent images in Unity.

Tiles are small square images used to build bigger scenes. Sprites are 2D images in Unity that tiles use. You import sprite images and slice them into tiles to use in your tilemap.

Result

You can see individual tile images ready to be placed on a grid.

Knowing that tiles are just small images helps you understand how complex scenes are built from simple parts.

2

Foundation

Creating a Tilemap and Grid

Concept: Set up the basic structure in Unity to hold and organize tiles.

In Unity, create a Grid object which acts like graph paper. Then add a Tilemap as a child to the Grid. The Tilemap holds the tiles you paint. This setup organizes tiles in rows and columns.

Result

You have a grid and tilemap ready to paint tiles onto.

Understanding the grid as the foundation helps you see how tiles align perfectly without overlap.

3

Intermediate

Using the Tile Palette Window

🤔Before reading on: do you think you can paint multiple tiles at once or only one tile at a time? Commit to your answer.

Concept: Learn to create and use a Tile Palette to select and paint tiles easily.

Open the Tile Palette window in Unity. Create a new palette and drag your sliced tiles into it. This palette acts like a paintbrush set. Select a tile and paint it onto the Tilemap grid in the scene view.

Result

You can paint tiles onto your map by clicking or dragging, building your scene visually.

Knowing how the palette works lets you quickly switch tiles and paint large areas efficiently.

4

Intermediate

Editing and Erasing Tiles

Concept: Learn how to modify or remove tiles after painting.

Use the erase tool in the Tile Palette to remove tiles from the Tilemap. You can also select tiles and replace them by painting over. This lets you fix mistakes or change your design easily.

Result

You can update your tilemap without starting over.

Understanding editing tools prevents frustration and encourages experimentation.

5

Intermediate

Using Tilemap Collider for Interaction

Concept: Add collision to your tilemap so game characters can interact with the world.

Add a Tilemap Collider 2D component to your Tilemap object. This creates invisible boundaries matching your tiles. Characters can then walk on or collide with tiles as expected.

Result

Your tilemap now affects gameplay physics and interactions.

Knowing how to add colliders connects visual design with game mechanics.

6

Advanced

Optimizing Tilemaps for Performance

🤔Before reading on: do you think more tilemap layers always improve visuals without cost? Commit to your answer.

Concept: Learn techniques to keep your game running smoothly with large tilemaps.

Use chunking to divide tilemaps into smaller parts. Avoid too many tilemap layers. Use Unity’s built-in optimizations like Sprite Atlas to reduce draw calls. This keeps frame rates high even with big maps.

Result

Your game runs faster and uses less memory.

Understanding performance helps you build bigger worlds without slowing the game.

7

Expert

Custom Tile Behaviors and Animated Tiles

🤔Before reading on: do you think tilemaps can only show static images? Commit to your answer.

Concept: Create tiles that do more than just display images, like animations or special effects.

Write custom scripts inheriting from TileBase to define tile behavior. Use Animated Tile assets to cycle through images for effects like water or fire. This adds life and interactivity to your tilemaps.

Result

Your tilemap can display animations and respond to game events.

Knowing tilemaps can be dynamic expands creative possibilities beyond static maps.

Under the Hood

Unity’s Tilemap system uses a Grid component to define a coordinate system. Each tile is stored as data referencing a sprite and optional properties. When painting, Unity updates the Tilemap’s internal data structure and renders the correct sprites at grid positions. Colliders are generated based on tile shapes. Animated tiles update their sprites each frame using Unity’s animation system.

Why designed this way?

Tilemaps were designed to simplify 2D world building by abstracting repetitive image placement into a grid system. This reduces manual work and errors. The grid ensures alignment and easy calculations for physics and rendering. The system balances flexibility with performance by batching tiles and supporting custom behaviors.

┌───────────────┐
│ Grid System   │
│ (coordinates) │
└──────┬────────┘
       │
┌──────▼────────┐
│ Tilemap Data  │
│ (tile info)   │
└──────┬────────┘
       │
┌──────▼────────┐
│ Renderer      │
│ (draw sprites)│
└──────┬────────┘
       │
┌──────▼────────┐
│ Collider Gen  │
│ (physics)     │
└───────────────┘

Myth Busters - 4 Common Misconceptions

Quick: Do you think tilemaps only work for square tiles? Commit to yes or no.

Common Belief: Tilemaps only support square tiles of the same size.

Reality: Unity tilemaps support different tile sizes and shapes using custom tile assets and can handle hexagonal or isometric grids.

Why it matters: Believing tilemaps are limited stops you from exploring creative map styles and using Unity’s full capabilities.

Quick: Do you think painting tiles changes the original sprite images? Commit to yes or no.

Common Belief: Painting tiles modifies the original sprite images permanently.

Reality: Painting tiles only places references to sprites on the grid; the original images remain unchanged.

Why it matters: Misunderstanding this can cause fear of damaging assets and prevent experimentation.

Quick: Do you think adding many tilemap layers has no impact on game performance? Commit to yes or no.

Common Belief: More tilemap layers do not affect game performance significantly.

Reality: Each tilemap layer adds draw calls and memory use, which can slow down the game if overused.

Why it matters: Ignoring performance costs leads to laggy games and poor player experience.

Quick: Do you think tilemaps can only display static images? Commit to yes or no.

Common Belief: Tilemaps cannot show animations or dynamic content.

Reality: Tilemaps support animated tiles and custom tile scripts to create dynamic visuals.

Why it matters: Missing this limits the visual richness and interactivity of your game worlds.

Expert Zone

1

Tilemap chunking internally groups tiles to optimize rendering and collision checks, but chunk size affects performance and memory tradeoffs.

2

Custom tile scripts can override how tiles behave during runtime, enabling complex interactions like changing appearance based on game state.

3

Using Sprite Atlases with tilemaps reduces draw calls but requires careful management to avoid texture bleeding and maintain pixel-perfect visuals.

When NOT to use

Tilemap painting is not ideal for highly detailed or irregular 3D environments where meshes and models are better. For fully dynamic or destructible terrain, voxel or mesh-based systems may be more suitable.

Production Patterns

Professionals use layered tilemaps for backgrounds, collision, and decoration separately. They combine tilemap painting with procedural generation for large worlds. Animated tiles and custom scripts add polish and interactivity. Performance tuning with chunking and atlases is standard in shipped games.

Connections

Pixel Art

Tilemap painting builds directly on pixel art by arranging pixel images into scenes.

Understanding pixel art helps create tiles that look good when repeated and combined in tilemaps.

Graph Theory

Tilemaps can be seen as grids representing graphs where each tile is a node connected to neighbors.

Knowing graph theory helps with pathfinding and procedural map generation on tilemaps.

Mosaic Art

Tilemap painting shares the same principle as mosaic art: assembling small pieces to form a larger image.

Recognizing this connection shows how artistic concepts influence digital game design.

Common Pitfalls

#1 Painting tiles without setting the correct grid size causes misaligned tiles.

Wrong approach:

Using tiles of 32x32 pixels on a grid set to 16x16 pixels.

Correct approach:

Ensure the grid cell size matches the tile size, e.g., 32x32 pixels grid for 32x32 tiles.

Root cause:

Misunderstanding that grid cell size must match tile dimensions for proper alignment.

#2 Forgetting to add a Tilemap Collider when expecting collisions.

Wrong approach:

Painting walls but not adding any collider component to the Tilemap.

Correct approach:

Add a Tilemap Collider 2D component to the Tilemap to enable collisions.

Root cause:

Confusing visual tiles with physical colliders; they are separate components.

#3 Using too many tilemap layers without optimization leads to slow performance.

Wrong approach:

Stacking dozens of tilemap layers for minor visual effects without batching.

Correct approach:

Limit layers, combine tiles where possible, and use Sprite Atlases to optimize rendering.

Root cause:

Not understanding the rendering cost of multiple layers and draw calls.

Key Takeaways

Tilemap painting lets you build 2D game worlds by placing small images on a grid, making level design faster and organized.

The Grid and Tilemap components in Unity work together to align tiles perfectly and manage their data and rendering.

Using the Tile Palette window is key to selecting and painting tiles efficiently, including editing and erasing.

Adding colliders to tilemaps connects visuals with gameplay by enabling physics interactions.

Advanced tilemaps can include animations and custom behaviors, expanding creative possibilities beyond static images.