biome

uniform int biome;

This uniform identifies the biome currently occupied by the player. It’s value can be compared with the same predefined constants as custom uniforms using biome, for example: BIOME_PLAINS, BIOME_RIVER, BIOME_DESERT, BIOME_SWAMP, etc. For more information on biomes, see the Minecraft Wiki.

This uniform functions similarly to the value available for custom unfiroms in Optifine, however Iris additionally provides them as standard uniforms.