minecraft-assets/assets/minecraft/blockstates/purpur_pillar.json

{
    "variants": {
        "axis=y": { "model": "purpur_pillar_top" },
        "axis=z": { "model": "purpur_pillar_top", "x": 90 },
        "axis=x": { "model": "purpur_pillar_top", "x": 90, "y": 90 }
    }
}