Unity 2D Tilemap Tutorial for Procedural Level Generation

Welcome to the ultimate guide on creating dynamic, procedurally generated levels using Unity's 2D Tilemap system. If you've ever dreamed of building games with endless replayability, where every playthrough offers a new and unique world, then you've come to the right place. Procedural generation can seem like a complex and intimidating topic, but this tutorial will break it down into clear, manageable steps.

We will journey from the very basics of setting up a Unity project for tilemaps to implementing powerful algorithms that can generate organic caves, structured dungeons, and natural-looking terrain. You will learn not just the theory but also the practical C# code needed to bring these random worlds to life. We'll cover everything from generating the map data to visualizing it, adding collision for your players, and using advanced tools like Rule Tiles to make your levels look beautiful automatically.

This tutorial is designed for beginners who have a basic understanding of the Unity editor and some familiarity with C# scripting. By the end, you'll have a solid foundation in procedural generation techniques that you can adapt and expand upon for your own unique game projects.

Getting Started: Setting Up Your Unity Project

Before we can write a single line of generation code, we need to prepare our project. A proper foundation is key to a smooth workflow. Let's get Unity ready for tile-based creation.

First, create a new project in Unity Hub. Make sure you select the 2D (Core) template. This template comes with several packages and settings pre-configured for 2D development, which will save us some time.

Once the project is open, we need to verify that the necessary tool is installed. Go to the top menu and select Window > Package Manager. In the Package Manager window, make sure the filter is set to "Unity Registry". In the search bar, type "2D Tilemap Editor". It should already be installed and have a green checkmark next to it if you used the 2D template. If not, simply select it and click the "Install" button. This package gives us all the tools we need to work with tilemaps.

Now, let's create our first tilemap. In the Hierarchy window, which lists all the objects in your scene, right-click > 2D Object > Tilemap. You will notice that this doesn't just create one object; it creates a "Grid" GameObject with a child "Tilemap" GameObject. The Grid object is crucial because it defines the cell size and layout for all tilemaps that are its children. This allows you to have multiple tilemap layers—for example, a background layer, a main ground layer, and a foreground layer—that all align perfectly.

To draw on our tilemap, we need a palette of tiles. Think of this as an artist's paint palette. Go to Window > 2D > Tile Palette. This will open a new window. It will be empty at first. Click the "Create New Palette" button. Give your palette a name, like "LevelPalette", and choose a location to save it inside your project's Assets folder.

Of course, a palette is useless without colors, or in our case, tiles. Tiles are created from sprites. You'll need a sprite sheet for your level's art. This is a single image file containing all the different tile variations you want to use. For this tutorial, you can find many free tile assets on sites like Itch.io or the Unity Asset Store. Once you have a sprite sheet image, import it into your Unity project.

Select the imported image in your Project window. In the Inspector, you'll need to change a few settings. Set the "Texture Type" to "Sprite (2D and UI)". Set the "Sprite Mode" to "Multiple". This tells Unity that the image contains multiple separate sprites. Finally, find the "Pixels Per Unit" setting. This is important for scale. If your tiles are, for instance, 16x16 pixels, setting Pixels Per Unit to 16 means that one tile will equal one unit in Unity's world space. Click "Apply" to save these changes.

Now, click the "Sprite Editor" button in the Inspector. In the Sprite Editor window, click the "Slice" dropdown. Change the "Type" to "Grid By Cell Size". In the "Pixel Size" fields, enter the dimensions of your individual tiles (e.g., 16 for X and 16 for Y). Click the "Slice" button, and you should see blue outlines appear around each tile in your sheet. Click "Apply" in the top right of the Sprite Editor window and then close it.

You have successfully prepared your art. Now, drag the sprite sheet asset from your Project window directly into the Tile Palette window. Unity will ask where you want to save the new Tile assets it's about to create. Choose a folder, and Unity will automatically generate a separate Tile asset for each sliced sprite.

You are now ready to build! In the Tile Palette window, you can select a tile, choose the brush tool, and click and drag in your Scene view to paint tiles onto the tilemap. Try it out to make sure everything is working before we move on to automation.

The Algorithms: Core of Procedural Generation

With our project set up, we can now dive into the exciting part: the code that will generate our levels. The fundamental idea behind our procedural generation is to first create a data model of our map, and then use that model to place the actual tiles. We will represent our map as a two-dimensional array of integers, where a 0 might represent an empty space and a 1 might represent a solid floor tile.

Create a new C# script in your project. Let's call it MapGenerator. This script will be the brain of our operation, containing the logic for our generation algorithms.

Algorithm 1: Simple Random Walk

The Random Walk algorithm, also known as Drunkard's Walk, is a fantastic starting point. It's simple to understand and produces surprisingly organic, natural-looking cave systems. The concept is to imagine a "digger" or "walker" that starts at a point on the map and then moves in a random direction for a set number of steps, carving out a path of floor tiles as it goes.

The process looks like this:

1. Initialize a 2D array for your map data.

2. Pick a starting position for the walker, for example, the center of the map.

3. Start a loop that runs for a predefined number of iterations (the "walk length").

4. Inside the loop, mark the walker's current position in the array as a floor tile.

5. Choose a random direction (up, down, left, or right).

6. Update the walker's position based on that direction.

7. Add a check to make sure the walker doesn't go outside the map boundaries.

8. Repeat until the loop finishes.

This basic algorithm is powerful, but you can easily extend it. What if you had multiple walkers starting from different points? These small variations can lead to much more complex and interesting level layouts.

Algorithm 2: Perlin Noise

For creating more top-down, terrain-like maps, such as islands or continents, Perlin Noise is an invaluable tool. Perlin Noise is not completely random; it generates a smoothly transitioning pattern of values. Think of it like a procedurally generated cloud texture.

Unity provides a built-in function for this: Mathf.PerlinNoise. This function takes two coordinates (an x and a y) and returns a float value between 0.0 and 1.0. To use Perlin Noise, you iterate through every cell of your map grid and use the noise value to decide whether to place a tile. To control the "zoom level" of the noise, you multiply the coordinates by a scale factor. A smaller scale value zooms out, creating larger, smoother features.

The implementation steps are:

1. Define map dimensions, a noise scale, and a random offset.

2. Loop through every x and y position of your map.

3. Get the Perlin value for that position, adjusted by your scale and offset.

4. Compare this value to a threshold. For example, if the value is greater than 0.5, place a ground tile. Otherwise, leave it empty.

5. After the loops complete, you'll have a map that resembles a natural landscape.

Algorithm 3: Cellular Automata

Cellular Automata is an algorithm that excels at creating organic cave structures. It works by simulating a simple form of life or growth. The state of each cell in the grid (whether it's a wall or a floor) is determined by the state of its neighbors.

The process typically starts with a map filled with random noise (e.g., 45% of the map is walls). Then, you apply a set of simple rules to it over several iterations to "smooth" it out.

A common rule set is:

• A wall tile becomes a floor tile if it has too few wall neighbors.

• A floor tile becomes a wall tile if it has a large number of wall neighbors.

By running this smoothing process for 4 or 5 iterations, the initial random noise coalesces into large, smooth, and very natural-looking cave systems.

Visualizing the Map and Adding Collision

Generating a 2D array of numbers is great, but it's not a level yet. We need to translate that data into actual tiles in our scene. For this, we'll create a second script, let's call it TilemapVisualizer.

This script will have a public method that takes the generated 2D array and loops through it. Whenever it finds a cell that should have a tile, it uses the command tilemap.SetTile(position, tile) to place the correct tile in the scene.

Now for collision. Select your Tilemap GameObject in the Hierarchy.

1. Click Add Component and add a Tilemap Collider 2D. This creates a collider for every single tile.

2. For better performance, click Add Component again and add a Composite Collider 2D.

3. Unity will add a Rigidbody 2D. Change its Body Type to Static.

4. Finally, go back to the Tilemap Collider 2D and check the box that says Used by Composite.

This merges all the individual colliders into one single, optimized collider for your level.

Advanced Workflow: Rule Tiles

Manually placing edge and corner tiles is tedious. Rule Tiles automate this. A Rule Tile is a special type of tile that automatically changes its sprite based on its neighbors. You can create one from the Assets menu (Create > 2D > Tiles > Rule Tile) after installing the 2D Tilemap Extras package.

In the Rule Tile's inspector, you can define rules. For example: "If the tile above me is not this tile, use the top-edge sprite." By setting up rules for all edges and corners, you can simply paint with one single Rule Tile, and it will automatically create a beautiful, finished-looking environment.

Conclusion

You have now explored the complete pipeline of procedural level generation in Unity. We started with the essential project setup, delved into powerful algorithms like Random Walk, Perlin Noise, and Cellular Automata, and learned how to translate that data into a visual and collidable level.

The true power of procedural generation lies in experimentation. Tweak the parameters of the algorithms. Combine them. The techniques you've learned here are the building blocks for creating your own unique worlds, full of endless variety and surprise. Now go forth and generate something amazing