Minecraft structures

Most structures are placed on a region grid. The world is divided into squares of spacing chunks, and one candidate position is chosen inside each square with a random number generator seeded from the region coordinates, the world seed and a per-structure salt. Separation is the minimum gap kept between neighbouring regions, which stops two structures from generating right next to each other across a region border.

After picking the position, Minecraft checks the biome or terrain there. That is why the map marks some layers as candidates: the grid position is exact, the biome check is not performed unless the generation engine is available. Read the data reference →