Appearances：折叠图纸可呈现的外观
GET /appearances 列出 Fold 可用于显示图纸的外观：金属、纸板、瓦楞纸板（单层、双层和三层）、硬纸板、织物、塑料和橡胶、木材 … 每种外观都有其 id（即
/fold 在 appearance 中接受的值）、name、所属组（category），以及会选用它的材料名称（match）。该请求没有正文。
示例
GET /appearances
X-API-KEY: your-api-key
[
{ "id": "cotton-jersey", "name": "Cotton jersey, white", "category": "Apparel and textiles", "match": ["Cotton jersey", "Jersey", "T-shirt", "Single jersey"] },
…
{ "id": "corrugated-bc-kraft", "name": "BC double wall, kraft", "category": "Corrugated", "match": ["BC double", "BC flute", "CB double", "Double wall"] },
…
{ "id": "gc2-board", "name": "GC2 folding boxboard, white back", "category": "Paperboard", "match": ["GC2", "GC1", "Folding boxboard", "Folding boxboard GC2", "FBB", "Boxboard"] },
…
]
如果未向 /fold 提供 appearance，它会选择 match 名称与图纸材料（其 T
选项）相符的外观，否则使用普通白色纸板。