Load default image from assets in callbacks

app.py

@@ -359,6 +359,15 @@ def preprocess_image_only(img: Optional[Image.Image]) -> Optional[Image.Image]:
     return _preprocess_to_518(img)
 
 
+def _resolve_input_image(image_input: Optional[Image.Image]) -> Image.Image:
+    """Use the bundled example directly from assets when no image is selected."""
+    if image_input is not None:
+        return image_input
+    if DEFAULT_IMAGE.exists() and not _path_is_git_lfs(DEFAULT_IMAGE):
+        return Image.open(DEFAULT_IMAGE).convert("RGBA")
+    raise gr.Error("Upload an input image first.")
+
+
 # ── SLaT I/O ──────────────────────────────────────────────────────────────────
 
 def _save_slat(slat: Any, path: Path) -> None:
@@ -428,12 +437,10 @@ def generate_geometry(
     progress: gr.Progress = gr.Progress(track_tqdm=True),
 ) -> tuple[Dict[str, Any], str, str]:
     """① Hunyuan3D geometry generation."""
-    if image_input is None:
-        raise gr.Error("Upload an input image first.")
     session_dir = CACHE_DIR / str(req.session_hash)
     session_dir.mkdir(parents=True, exist_ok=True)
 
-    rgba = _ensure_rgba(image_input)
+    rgba = _ensure_rgba(_resolve_input_image(image_input))
     if rgba.size != (518, 518):
         progress(0.1, desc="Preprocessing image")
         rgba = _preprocess_to_518(rgba)
@@ -469,14 +476,12 @@ def generate_slat(
     mesh_path = asset_state.get("mesh_path")
     if not mesh_path or not os.path.isfile(mesh_path):
         raise gr.Error("Run **① Geometry** first (or upload a mesh).")
-    if image_input is None:
-        raise gr.Error("Upload an input image.")
     session_dir = CACHE_DIR / str(req.session_hash)
 
     progress(0.1, desc="Loading mesh")
     mesh = trimesh.load(mesh_path, force="mesh")
 
-    rgba = _ensure_rgba(image_input)
+    rgba = _ensure_rgba(_resolve_input_image(image_input))
     if rgba.size != (518, 518):
         rgba = _preprocess_to_518(rgba)
     slat_img = _flatten_rgba(rgba, (0.0, 0.0, 0.0))