biome_category

uniform int biome_category;

This uniform identifies the biome category currently occupied by the player. It’s value can be compared with the same predefined constants as custom uniforms, the following are recognized:

CAT_NONE, CAT_TAIGA, CAT_EXTREME_HILLS, CAT_JUNGLE, CAT_MESA, CAT_PLAINS, CAT_SAVANNA, CAT_ICY, CAT_THE_END, CAT_BEACH, CAT_FOREST, CAT_OCEAN, CAT_DESERT, CAT_RIVER, CAT_SWAMP, CAT_MUSHROOM, CAT_NETHER

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.