feat: add on-demand format conversion support (FBX, STL, USDZ, MP4, GIF)

- Discover /creations/resourceConvert endpoint via browser inspection
- Add resource_convert() method to api.py and api_complete.py
- Extend MODEL_FORMAT_KEYS with fbx, stl, usdz, mp4, gif
- Update get_model_urls() and download_model() with include_converted flag
- Update CLI with --converted flag for formats and download commands
- Update reverse engineering docs with native vs converted format tables

hunyuan3dweb/api.py

@@ -19,7 +19,9 @@ API_BASE = f"{BASE_URL}/api/3d"
 class Hunyuan3DAPI:
     """腾讯混元3D API客户端"""
 
-    # 模型下载格式键名（与腾讯混元3D API返回的 urlResult 字段对应）
+    # 模型下载格式键名
+    # 原生格式：直接来自 API urlResult
+    # 转换格式：通过 /creations/resourceConvert 从 OBJ(zip) 转换得到
     MODEL_FORMAT_KEYS = [
         "glb",          # 带PBR贴图的GLB二进制模型
         "obj",          # OBJ模型（通常打包在zip中）
@@ -35,6 +37,11 @@ class Hunyuan3DAPI:
         "pbrNormalImage",     # PBR法线贴图
         "invisible_wall",     # 不可见碰撞墙
         "air_wall",           # 空气墙（碰撞体）
+        "fbx",          # FBX 格式（转换）
+        "stl",          # STL 格式（转换）
+        "usdz",         # USDZ 格式（转换，用于 iOS AR）
+        "mp4",          # MP4 视频格式（转换）
+        "gif",          # GIF 动图格式（转换）
     ]
 
     def __init__(self, cookies: Optional[str] = None):
@@ -200,10 +207,41 @@ class Hunyuan3DAPI:
             "creationsId": creation_id
         })
 
-    def get_model_urls(self, creation_id: str) -> Dict[str, Optional[str]]:
+    def resource_convert(self, source_url: str, target_formats: List[str]) -> Dict[str, str]:
+        """
+        调用资源转换接口将 OBJ(zip) 转换为其他格式
+
+        Args:
+            source_url: OBJ zip 文件的 URL（来自 urlResult['obj']）
+            target_formats: 目标格式列表，如 ["usdz", "fbx"]
+
+        Returns:
+            格式键名 -> 转换后下载URL 的字典
+        """
+        data = {
+            "sourceResource": [
+                {"format": "zip", "url": source_url}
+            ],
+            "targetFormatList": target_formats
+        }
+        resp = self._make_request("POST", "/creations/resourceConvert", data=data)
+        result = {}
+        for item in resp.get("convertResult", []):
+            fmt = item.get("format")
+            url = item.get("url")
+            if fmt and url:
+                result[fmt] = url
+        return result
+
+    def get_model_urls(self, creation_id: str, include_converted: bool = False) -> Dict[str, Optional[str]]:
         """
         获取指定创作所有可用格式的下载URL
 
+        Args:
+            creation_id: 创作ID
+            include_converted: 是否包含转换格式（fbx/stl/usdz/mp4/gif），
+                               启用时会调用 resourceConvert 接口
+
         Returns:
             格式键名 -> 下载URL 的字典，空值已被过滤
         """
@@ -220,14 +258,26 @@ class Hunyuan3DAPI:
             return {}
 
         url_result = result_list[0].get("urlResult", {})
-        return {
+        urls = {
             key: val
             for key in self.MODEL_FORMAT_KEYS
             if (val := url_result.get(key)) and val not in (None, "", {})
         }
 
+        if include_converted:
+            obj_url = urls.get("obj")
+            if obj_url:
+                converted = self.resource_convert(
+                    obj_url,
+                    ["fbx", "stl", "usdz", "mp4", "gif"]
+                )
+                urls.update(converted)
+
+        return urls
+
     def download_model(self, creation_id: str, format_key: str = "glb",
-                       output_path: Optional[str] = None) -> str:
+                       output_path: Optional[str] = None,
+                       include_converted: bool = False) -> str:
         """
         下载指定格式的模型文件
 
@@ -239,7 +289,7 @@ class Hunyuan3DAPI:
         Returns:
             实际保存的本地文件路径
         """
-        urls = self.get_model_urls(creation_id)
+        urls = self.get_model_urls(creation_id, include_converted=include_converted)
         if format_key not in urls:
             available = ", ".join(urls.keys())
             raise ValueError(