Biomes

Biomes are regions with differing foliage, terrain etc.

Biome List
Lookup table
Biome Noise
1. Noise Octaves
2. Biome map
Further reading

The seed used throughout all of these examples is 3257840388504953787, the seed behind pack.png.

Biome List

There exist 13 distinct Biomes in Beta 1.7.3. They each have unique properties, mainly if they can show rain particles, if it can snow in them, and what their respective foliage and map colors are.

Name	Top Block	Filler Block	Rain	Snow	Foliage Color	Map Color
Rainforest	Grass	Dirt	✅	❌	`#1FF458`	`#8FA360`
Swampland	Grass	Dirt	✅	❌	`#8BAF48`	`#7F9B20`
Seasonal Forest	Grass	Dirt	✅	❌	`#4EE031`	`#9BE023`
Forest	Grass	Dirt	✅	❌	`#4EBA31`	`#566210`
Savanna	Grass	Dirt	✅	❌	`#4EE031`	`#D9E023`
Shrubland	Grass	Dirt	✅	❌	`#4EE031`	`#A1AD20`
Taiga	Grass	Dirt	✅	✅	`#7BB731`	`#2EB153`
Desert	Sand	Dirt	❌	❌	`#4EE031`	`#FA9418`
Plains	Grass	Dirt	✅	❌	`#4EE031`	`#FFD910`
Ice Desert	Grass	Sand	❌	✅	`#C4D339`	`#FFED93`
Tundra	Grass	Dirt	✅	✅	`#C4D339`	`#57EBF9`
Hell	Grass	Dirt	❌	❌	`#4EE031`	`#FF0000`
Sky	Grass	Dirt	❌	❌	`#4EE031`	`#8080FF`

Lookup table

A 64x64 lookup table is generated to more quickly calculate the appropriate biome to use.

Biome GetBiome(float temperature, float humidity) {
    humidity *= temperature;
    if (temperature < 0.1) {
        return tundra;
    }
    if (humidity < 0.2) {
        if (temperature < 0.5) {
            return tundra;
        }
        if (temperature < 0.95) {
            return savanna;
        }
        return desert;
    }
    if (humidity > 0.5 && temperature < 0.7) {
        return swampland;
    }
    if (temperature < 0.5) {
        return taiga;
    }
    if (temperature < 0.97) {
        if (humidity < 0.35) {
            return shrubland;
        }
        return forest;
    }
    if (humidity < 0.45) {
        return plains;
    }
    if (humidity < 0.9) {
        return seasonalForest;
    }
    return rainforest;
}

If mapped to an image, using the foliage/map colors, we get this.

Foliage Colors	Map Colors

_{Temperature is X, Humidity is Y. Range is from 0 to 64 (or 0.0 to 1.0) on both axes. Notch drew this graph back in 2011.}

Biome Noise

The function which determines what biome is use in a chunk is relatively simple. It mainly uses 3 Octave Simplex Noise Generators.

Noise Octaves

The current Chunk Coordinate, scaled to Block-Space (multiplied by 16), is passed in, alongside how many values the generator should return (16x16 for one chunk) and a scaling factor.

Generator	Octaves	Scale
Temperature	`4`	`(0.025, 0.025, 0.25)`
Humidity	`4`	`(0.05, 0.05, 1/3)`
Variation	`2`	`(0.25, 0.25, 0.5882352941176471)`

Each of these return a 16x16 array of 64-Bit floating point numbers, which’re that chunks’ temperature, humidity and variation values.

Temperature	Humidity	Variation

_{Temperature, humidity and variation values from chunk -1,-1 to 1,1. These values are in the 0.0 - 2.0 range.}

Biome map

The final biomes for each section are determined by iterating over the 16x16 array and performing the following actions for each entry.

for (int i = 0; i < 16*16; i++) {
    double vari = variation[i] * 1.1 + 0.5;
    double scale = 0.01;
    double max = 1.0 - scale;
    double temp = (temperature[i] * 0.15 + 0.7) * max + vari * scale;
    scale = 0.002;
    max = 1.0 - scale;
    double humi = (humidity[i] * 0.15 + 0.5) * max + vari * scale;
    temp = 1.0 - (1.0 - temp) * (1.0 - temp);
    // Limit values to 0.0 - 1.0
    if(temp < 0.0) temp = 0.0;
    if(humi < 0.0) humi = 0.0;
    if(temp > 1.0) temp = 1.0;
    if(humi > 1.0) humi = 1.0;

    temperature[i] = temp;
    humidity[i] = humi;
    // Get the biome from the lookup
    biomeMap[i] = GetBiomeFromLookup(temp, humi);
}

The returned biome map can look something like this over a 3x3 chunk area.

Foliage Colors	Map Colors

The temperature and humidity values are changed by this function, resulting in a different set of values, to be used in later generation stages.

Temperature	Humidity	Variation

_{Temperature, humidity and Variation values from chunks -1,-1 to 1,1 after being modified by this function. These values are in the 0.0 - 2.0 range. Variation is not affected.}

This is then passed to the World Generator.