ModelTranslator: bl_decimate 抽取 UV 几何到 sidecar JSON

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Tools/ModelTranslator/bl_decimate.py

@@ -326,6 +326,21 @@ def _do_unwrap(obj, mode, warnings):
     return m
 
 
+def _collect_uv_polygons(obj):
+    """提取每个面的 UV 多边形（归一化坐标）：[[[u,v], ...], ...]，供外部 PIL 绘图。
+    无 UV 层返回空列表。"""
+    import bmesh
+    bm = bmesh.new()
+    bm.from_mesh(obj.data)
+    uv = bm.loops.layers.uv.active
+    polys = []
+    if uv is not None:
+        for f in bm.faces:
+            polys.append([[l[uv].uv.x, l[uv].uv.y] for l in f.loops])
+    bm.free()
+    return polys
+
+
 def main():
     import bpy
     import json
@@ -364,6 +379,17 @@ def main():
             warnings.append("修正 %d 轮后仍超差：%d 面（目标 %d ±3%%）" % (MAX_RETRY, cur, target))
 
     uv_info = _do_unwrap(obj, unwrap_mode, warnings)
+    uv_png = os.path.splitext(os.path.abspath(out_fbx))[0] + "_uv.png"
+    uv_polys_json = os.path.splitext(os.path.abspath(out_fbx))[0] + "_uv.polys.json"
+    uv_preview = None
+    try:
+        polys = _collect_uv_polygons(obj)
+        os.makedirs(os.path.dirname(uv_polys_json), exist_ok=True)
+        with open(uv_polys_json, "w", encoding="utf-8") as fp:
+            json.dump(polys, fp)
+        uv_preview = uv_png   # 目标 PNG；实际绘制由 model_decimate（系统 Python + PIL）完成
+    except Exception as e:
+        warnings.append("UV 几何导出失败（%s），跳过观察图" % e)
     out_dir = os.path.dirname(os.path.abspath(out_fbx))
     os.makedirs(out_dir, exist_ok=True)
     # 仅导出合并后的对象；整场景导出会把 armature/empty 等非 mesh 带进 _low.fbx
@@ -373,7 +399,11 @@ def main():
     print("MT_SUMMARY " + json.dumps(
         {"src": os.path.basename(src), "fbx": os.path.basename(out_fbx),
          "tris_before": orig, "tris_after": cur, "target": target,
-         "uv": uv_info, "warnings": warnings}, ensure_ascii=False))
+         "uv": uv_info,
+         "uv_preview": uv_preview,
+         "uv_polys": uv_polys_json if uv_preview else None,
+         "warnings": warnings},
+        ensure_ascii=False))
 
 
 if __name__ == "__main__" and "--" in sys.argv: