Procedural caves are a popular feature in many sandbox and exploration games. Instead of manually designing cave systems, procedural generation allows developers to create natural-looking underground environments automatically.

Games such as Minecraft, Terraria, and No Man’s Sky use procedural cave generation to build massive underground worlds.

One of the most common techniques used for cave generation is Cellular Automata.

What Is Cellular Automata?

Cellular automata is a simulation technique where a grid of cells evolves over time based on simple rules.

Each cell can be either:

• Wall
• Empty space

By repeatedly applying rules to neighboring cells, the map slowly turns into natural cave shapes.

Step 1: Creating the Cave Grid

First, we create a 2D grid that represents the cave layout.

int width = 100;
int height = 100;

int[,] map = new int[width, height];

In this grid:

• 1 = wall
• 0 = empty space

Step 2: Randomly Fill the Map

Next, we fill the grid with random walls.

void RandomFillMap()
{
    for (int x = 0; x < width; x++)
    {
        for (int y = 0; y < height; y++)
        {
            if (Random.value < 0.45f)
                map[x, y] = 1;
            else
                map[x, y] = 0;
        }
    }
}

This creates a noisy map that will later evolve into caves.

Step 3: Apply Cellular Automata Rules

We now simulate cave formation using neighbor rules.

int GetNeighbourWallCount(int x, int y)
{
    int count = 0;

    for(int nx = x - 1; nx <= x + 1; nx++)
    {
        for(int ny = y - 1; ny <= y + 1; ny++)
        {
            if(nx == x && ny == y)
                continue;

            if(nx < 0 || ny < 0 || nx >= width || ny >= height)
                count++;
            else
                count += map[nx, ny];
        }
    }

    return count;
}

Step 4: Smooth the Cave

We apply smoothing iterations to create natural cave shapes.

void SmoothMap()
{
    for(int x = 0; x < width; x++)
    {
        for(int y = 0; y < height; y++)
        {
            int neighbours = GetNeighbourWallCount(x, y);

            if(neighbours > 4)
                map[x, y] = 1;
            else if(neighbours < 4)
                map[x, y] = 0;
        }
    }
}

Running this function multiple times gradually produces cave-like structures.

Step 5: Converting the Grid into a Mesh

Once the cave map is generated, we need to convert it into a visible mesh in Unity.

A common technique for this is the Marching Squares algorithm.

This algorithm analyzes the surrounding cells and generates triangles to form cave walls.

The result is a smooth cave mesh rather than a blocky grid.

Adding Vertical Cave Depth

For 3D cave systems, you can extend the grid into a 3D volume.

int[,,] caveVolume = new int[width, height, depth];

This allows caves to have multiple levels and tunnels.

Connecting Cave Rooms

Sometimes cave systems create isolated rooms. To fix this, you can connect regions using tunnels.

Typical approach:

• Detect separate cave regions
• Find closest points between regions
• Create tunnels between them

This ensures the player can explore the entire cave network.

Adding Cave Decorations

After generating caves, you can populate them with objects such as:

• Stalagmites
• Crystals
• Underground lakes
• Minerals
• Enemies

Instantiate(crystalPrefab, position, Quaternion.identity);

Performance Tips

• Generate caves per chunk
• Use mesh simplification
• Use object pooling for cave props
• Generate caves asynchronously

Games Using Procedural Cave Generation

• Minecraft
• Terraria
• Deep Rock Galactic
• No Man’s Sky

Procedural cave generation allows these games to create massive underground systems with minimal manual design.

Final Thoughts

Procedural cave generation adds depth and exploration to procedural worlds.

By combining cellular automata, mesh generation, and chunk-based terrain systems, you can create complex underground environments that feel organic and natural.

Once integrated with your terrain generator, caves can become a core part of your game’s world design.