minecraft-assets/assets/minecraft/blockstates/bamboo_block.json

{
  "variants": {
    "axis=x": {
      "model": "minecraft:block/bamboo_block_x"
    },
    "axis=y": {
      "model": "minecraft:block/bamboo_block_y"
    },
    "axis=z": {
      "model": "minecraft:block/bamboo_block_z"
    }
  }
}