Biome Squisher

Instead of placing new biomes over the vanilla biome map, the library squishes vanilla biomes outward to open a hole for each injected biome. Borders between biomes stay in place, and each biome shrinks or grows by a share of its area, so rarities relative to one another are kept. Biomes that are squished shrink in a uniform way rather than being cut out entirely.

The injection is defined in datapacks. A series file names the dimension and the biome space to affect, and lists the squishers and the levels they apply to. Each injection states which biome it adds, where it is placed, and how large the injection is, from 0 for nothing up to 1 for the entire biome space. Multiple mods can inject into the same location, and their injections are layered on top of one another in a deterministic order, so they coexist without breaking each other's biomes.

Biome Squisher works on the noise biome source, and the math for squishing is handled by the library so mod authors do not have to deal with the edge cases themselves. It also provides an API for injecting extra biomes into the biome map. The library is server-side only, runs on Fabric, NeoForge and Quilt, and requires Fabric API on every loader.