feat(trellis): per-request UV atlas method, bump trellis to v0.2.1

docs/api/lemonade.md

@@ -772,6 +772,7 @@ This endpoint is not part of the OpenAI API, so it is a Lemonade-specific extens
 | `image` | Yes | Base64-encoded input image (optionally a `data:` URL). |
 | `resolution` | No | Cascade resolution: `512`, `1024`, or `1536`. Default: `512`. |
 | `bg_removal` | No | Background removal mode: `threshold` or `birefnet`. Use `birefnet` for photos with real backgrounds. |
+| `uv` | No | UV atlas method: `xatlas` (default) or `box`. `xatlas` runs a full UV unwrap giving every face unique atlas space — best quality, but chart computation is superlinear in face count. `box` is a faster 6-plane projection with occlusion-aware bucket assignment and depth-tested rasterization; small texture artifacts remain possible in concave regions. |
 | `seed` | No | Random seed for reproducibility. |
 | `response_format` | No | Output encoding. Only formats the backend natively produces are accepted (currently `glb`); other values are rejected with `400 Bad Request`. Default: `glb`. |
 

src/cpp/resources/backend_versions.json

@@ -122,9 +122,9 @@
     "cuda": "v0.1.1"
   },
   "trellis": {
-    "vulkan": "v0.1.5",
-    "rocm-stable": "v0.1.5",
-    "cuda": "v0.1.5"
+    "vulkan": "v0.1.6",
+    "rocm-stable": "v0.1.6",
+    "cuda": "v0.1.6"
   },
   "openmoss": {
     "vulkan": "v0.1.2",

src/cpp/server/backends/trellis/trellis_server.cpp

@@ -183,6 +183,9 @@ void TrellisServer::model_3d_generations(const json& request, httplib::DataSink&
     if (request.contains("bg_removal") && request["bg_removal"].is_string()) {
         fields.push_back({"bg_removal", request["bg_removal"].get<std::string>(), "", ""});
     }
+    if (request.contains("uv") && request["uv"].is_string()) {
+        fields.push_back({"uv", request["uv"].get<std::string>(), "", ""});
+    }
 
     auto fail = [&sink](const std::string& message) {
         const std::string payload =

src/cpp/server/server.cpp

@@ -3502,6 +3502,12 @@ void Server::handle_3d_generations(const httplib::Request& req, httplib::Respons
         if (request_json.contains("seed") && !request_json["seed"].is_number_integer()) {
             return reject("'seed' must be an integer");
         }
+        if (request_json.contains("uv")) {
+            const auto& u = request_json["uv"];
+            if (!u.is_string() || (u != "box" && u != "xatlas")) {
+                return reject("'uv' must be 'box' or 'xatlas'");
+            }
+        }
 
         std::string requested_model = request_json["model"];
         try {