Random Minecraft Block Generator

What a block is

A cube, one metre on each side, made of one substance. That is the entire vocabulary of the world, and everything you have ever built was a sentence in it.

A few of the blocks in this list:

• Bedrock
• Cobblestone
• Obsidian
• Sea Pickle
• Blue Ice
• Conduit
• Prismarine
• Air

Air is on that list, and it belongs there. Empty space is a block like any other, with a number, sitting in the same array as stone. The world has no holes in it. It is solid all the way through, and most of it is made of nothing.

Pulling a block

1. Press Generate for one block, which is a decent way to start a build you would never have planned.
2. Ask for five and restrict yourself to those, plus whatever you need to survive. It is the best building exercise there is.
3. Type into Contains to search, useful for pulling every variety of stone or wood.
4. Copy to keep your palette.

Where these blocks come from

Blocks gathered and checked by hand from across the game, a broad selection rather than every block in the current version. The tool picks from that pool in your browser.

The world does not exist until you walk into it

Start a new world. You are given a seed, which is just a number.

That number is the entire world. Not a pointer to it, not a compressed copy of it. The mountains, the caves, the ravine you fell into, the village on the plain, the exact position of every ore in every wall: all of it is a consequence of that one integer and the rules the game applies to it.

Nothing has been drawn. Nobody at the studio placed that cliff. Until you walk towards it, the cliff is not stored anywhere at all. When you get close enough, the game feeds your coordinates and the seed into a function, the function returns numbers, and the numbers become terrain, on the spot.

This is why the world can be effectively endless while the download is small. You are not carrying a world around with you. You are carrying the recipe, and the world is cooked to order.

Give the same seed to a friend on the other side of the planet and they get the same cliff, in the same place, down to the individual block. That is not a copy. It is the same calculation, run again.

The algorithm that won an Academy Award

The function at the heart of it has a name and an owner, and a slightly ridiculous history.

In the early 1980s, a young computer graphics researcher named Ken Perlin was working on the visual effects for the film Tron. He was unhappy with how the results looked. Computer generated surfaces were too clean. Too regular. Everything had the smoothness of a machine, and nothing in the real world is like that. But the alternative, pure randomness, is worse: pure randomness looks like television static, and no landscape is static.

What he wanted was something in between. Randomness that flows. Values that wander unpredictably but never jump, so that any two nearby points are similar and any two distant points are unrelated.

He built it. He described it publicly in a paper in 1985, and it entered the toolkit of every graphics programmer alive. It is called Perlin noise.

In 1997, the Academy of Motion Picture Arts and Sciences gave him an Academy Award for Technical Achievement for it. The citation says it produces natural appearing textures on computer generated surfaces.

So there is an Oscar sitting behind the hills you walked over this morning.

How a mountain is made out of noise

One layer of Perlin noise is disappointing. It gives you gentle rolling hills, all the same size, endlessly. It looks like a duvet.

The trick is to add the noise to itself at different scales, which graphics people call octaves, borrowing the word from music for exactly the right reason.

The first octave is broad and strong: it decides where the continents and the mountain ranges are. The second is twice as fine and half as loud: it puts hills on the mountains. The third puts ridges on the hills. The fourth roughens the surface of the ridges. Stack four to eight of these and you get terrain that has both a shape and a texture, because real landscapes have detail at every scale you care to look at.

Then it happens again for other things. A separate noise field decides where the caves are. Another decides temperature. Another decides rainfall. Put temperature and rainfall together and you have biomes: hot and dry is desert, cold and wet is taiga, and the boundaries between them are soft because noise is soft.

Nobody designed the desert you found. Two numbers crossed a threshold.

Why the world is made of cubes

It would be easy to assume the blocks are a stylistic choice, a look. They are a data structure, and the look came afterwards.

Consider what a cube grid buys you. Every position in the world is three whole numbers, so the game always knows exactly what is where without any geometry. Every block is one entry in an array, so a chunk of the world is a small block of memory. Placing and destroying are the same operation: change a number. And crucially, the terrain you dig into is made of the same stuff as the terrain you build with, so mining and building are the same verb.

That last point is the whole game. Most games separate scenery from inventory. The wall is scenery, the sword is an item, and you cannot turn one into the other. In a cube world the wall is the item. The mountain is a pile of things you can carry.

The blocky look is what you pay for that. It is a low price, and a generation of players decided it was not even a cost.

Questions people ask

What exactly is a seed?

A number that starts the sequence. The generator is not truly random; it is a deterministic function that behaves as though it were. Feed it the same number and it will produce the same world forever, on any machine, in any year.

Is the world really infinite?

Practically, not mathematically. Generation continues as far as you walk, but the numbers describing your position eventually get large enough that the arithmetic itself becomes unreliable, and the terrain starts behaving strangely. The world ends where the mathematics gives up.

What is the point of building with random blocks?

Constraint. Given everything, most people build the same house they built last time. Given four materials chosen by something with no taste, you are forced into decisions you would not have made, and that is where a personal style comes from.

Why is air a block?

Because it is simpler for the world to be a solid grid where every cell holds something, than a grid full of exceptions. Air is the block that means nothing is here. The absence has to be stored too.

References

1. Perlin noise, including the 1985 SIGGRAPH paper and the 1997 Academy Award citation. https://en.wikipedia.org/wiki/Perlin_noise
2. Perlin, K. (1985). An Image Synthesizer. SIGGRAPH Computer Graphics. https://dl.acm.org/doi/10.1145/325165.325247
3. Procedural terrain generation with Perlin noise, on octaves, persistence and layered noise fields for caves and biomes. https://www.jdhwilkins.com/mountains-cliffs-and-caves-a-comprehensive-guide-to-using-perlin-noise-for-procedural-generation/