---
title: How terrain is generated using the noise router
versions:
  - '1.18.2'
  - '1.19'
tags:
  - worldgen
  - noise
  - density
---

The noise router is a piece of configuration in [noise settings](/worldgen/noise-settings/). It's a collection of [density functions](/guides/density-functions/), some used for the biome layout, aquifers, or ore veins.

## Final density
The density function that decides the terrain is f`final_density`. This density function will be computed for every block position. If it returns a value greater than n`0` the default block will be placed, otherwise either air or the default fluid will be placed.

With this information we can make the most basic noise router, one where every density function is set to n`0`. As predicted, this will result in a void world. Similarly, setting j`"final_density": 1` will result in a world completely filled with stone.

**`data/minecraft/worldgen/noise_settings/overworld.json`**
```json
{
  "sea_level": 63,
  "disable_mob_generation": false,
  "aquifers_enabled": false,
  "ore_veins_enabled": false,
  "legacy_random_source": false,
  "default_block": {
    "Name": "minecraft:stone"
  },
  "default_fluid": {
    "Name": "minecraft:water",
    "Properties": {
      "level": "0"
    }
  },
  "noise": {
    "min_y": -64,
    "height": 384,
    "size_horizontal": 2,
    "size_vertical": 2{#[1.18.2] ,
    "sampling": {
      "xz_scale": 1,
      "y_scale": 1,
      "xz_factor": 80,
      "y_factor": 160
    },
    "bottom_slide": {
      "target": 0,
      "size": 0,
      "offset": 0
    },
    "top_slide": {
      "target": 0,
      "size": 0,
      "offset": 0
    },
    "terrain_shaper": {
      "offset": 0,
      "factor": 0,
      "jaggedness": 0
    } #}
  },
  "noise_router": {
    "barrier": 0,
    "fluid_level_floodedness": 0,
    "fluid_level_spread": 0,
    "lava": 0,
    "temperature": 0,
    "vegetation": 0,
    "continents": 0,
    "erosion": 0,
    "depth": 0,
    "ridges": 0,
    "initial_density_without_jaggedness": 0,
    "final_density": 0,
    "vein_toggle": 0,
    "vein_ridged": 0,
    "vein_gap": 0
  },
  "spawn_target": [],
  "surface_rule": {
    "type": "minecraft:sequence",
    "sequence": []
  }
}
```

## Flat world
Let's continue with a simple density function that creates a flat world at Y=n`128`. Instead of n`0`, we now have this as the f`final_density`:
```json
{
  "type": "minecraft:y_clamped_gradient",
  "from_y": -64,
  "to_y": 320,
  "from_value": 1,
  "to_value": -1
}
```
The image below illustrates how s`y_clamped_gradient` works. In this example positions at Y=n`-64` will get a density of n`1` and positions at Y=n`320` will get a density of n`-1`.

![illustration of Y coordinates getting mapped the [-1, 1] range](https://user-images.githubusercontent.com/17352009/170406782-f7331402-0149-47e1-871e-6aff0c1ab1be.png)

And the result looks like this:

![a flat world](https://user-images.githubusercontent.com/17352009/170412400-52b1db55-3daf-48a9-b436-22119fe9ba06.png)


## First noise
To bring some variety to the world we need noise. We can improve the existing density function by adding a noise to it, like this:
```json
{
  "type": "minecraft:add",
  "argument1": {
    "type": "minecraft:y_clamped_gradient",
    "from_y": -64,
    "to_y": 320,
    "from_value": 1,
    "to_value": -1
  },
  "argument2": {
    "type": "minecraft:noise",
    "noise": "minecraft:gravel",
    "xz_scale": 2,
    "y_scale": 0
  }
}
```

We get the following result. The height of the terrain is based on a noise that varies along the X and Z coordinates.

![terrain with random elevations](https://user-images.githubusercontent.com/17352009/170411319-2a797950-95c4-4b90-b1a5-ff2ae4ae66ef.png)

To make the terrain smoother, we can stretch the noise by altering the f`xz_scale` field. This is the result with j`"xz_scale": 0.5`:

![terrain with smooth hills](https://user-images.githubusercontent.com/17352009/170411382-6a84f017-5c71-4e63-b90d-c17104ef57b1.png)

To get overhangs, the noise also needs to vary along the Y coordinate. The following is with j`"xz_scale": 1` and j`"y_scale": 1`.

![](https://user-images.githubusercontent.com/17352009/170412018-757999be-4595-4be8-9943-a3d3395a2add.png)

## Splines
🚧 *to be continued* 🚧
