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+# 减面工具 UV 展开优化实现计划
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** `model_decimate.py` 的 UV 展开从 Smart UV Project 换成"锐边 seam + MINIMUM_STRETCH 展开 + 质量门自动回退"，大幅减少 UV 碎岛。
+
+**Architecture:** 纯逻辑（union-find 数岛、翻转/利用率计算）放 `bl_decimate.py` 顶部可单测区；Blender 侧新增 seam 展开路径与 bmesh 指标提取，质量门（翻转/重叠占比 >2%）触发时回退原 smart_project 路径。`MT_SUMMARY` 增加 `uv` 字段，CLI 增加 `--unwrap {seam,smart}`（默认 seam）。
+
+**Tech Stack:** Python 3 标准库、Blender 5.0（bpy/bmesh）、unittest。
+
+**设计文档:** `docs/superpowers/specs/2026-07-16-decimate-uv-seam-unwrap-design.md`
+
+**重要提醒:**
+- 仓库路径含 `#`（`D:\UD\AI\AIC#Project`），**bash 里所有路径必须加引号**
+- Blender：`D:\tools\blender-5.0.0-windows-x64\blender.exe`
+- 冒烟素材：`Tools/ModelTranslator/src/well1500.fbx`（149.9 万面）→ 5000 面
+- 产物（`_low.fbx`）不入 git，只提交代码/文档
+
+## 文件结构
+
+```
+Tools/ModelTranslator/
+  bl_decimate.py            # 修改：纯逻辑区加 3 函数+1 常量；Blender 区重构展开路径
+  model_decimate.py         # 修改：--unwrap 参数 + UV 指标打印
+  tests/test_bl_decimate.py # 修改：追加纯逻辑测试
+  README.md                 # 修改：--unwrap 说明（Task 3）
+```
+
+---
+
+### Task 1: UV 指标纯逻辑（TDD）
+
+**Files:**
+- Modify: `Tools/ModelTranslator/tests/test_bl_decimate.py`（文件末尾 `if __name__` 之前追加）
+- Modify: `Tools/ModelTranslator/bl_decimate.py`（纯逻辑区，`within_tolerance` 之后、`# ---------------- 以下仅在 Blender 内执行` 之前）
+
+- [ ] **Step 1: 追加失败测试**
+
+在 `tests/test_bl_decimate.py` 的 `if __name__ == "__main__":` 之前插入：
+
+```python
+class TestCountIslands(unittest.TestCase):
+    def test_no_faces(self):
+        self.assertEqual(bd.count_islands(0, []), 0)
+
+    def test_no_pairs_each_face_is_island(self):
+        self.assertEqual(bd.count_islands(3, []), 3)
+
+    def test_chain_merges_to_one(self):
+        self.assertEqual(bd.count_islands(4, [(0, 1), (1, 2), (2, 3)]), 1)
+
+    def test_two_groups(self):
+        self.assertEqual(bd.count_islands(5, [(0, 1), (3, 4)]), 3)  # {0,1} {2} {3,4}
+
+    def test_duplicate_pairs_ok(self):
+        self.assertEqual(bd.count_islands(2, [(0, 1), (1, 0), (0, 1)]), 1)
+
+
+class TestFlippedFraction(unittest.TestCase):
+    def test_empty_is_zero(self):
+        self.assertEqual(bd.flipped_fraction([]), 0.0)
+
+    def test_mixed(self):
+        self.assertAlmostEqual(bd.flipped_fraction([0.1, -0.2, 0.3, 0.4]), 0.25)
+
+    def test_all_positive(self):
+        self.assertEqual(bd.flipped_fraction([0.1, 0.2]), 0.0)
+
+
+class TestFillRatio(unittest.TestCase):
+    def test_sum(self):
+        self.assertAlmostEqual(bd.fill_ratio([0.2, 0.3]), 0.5)
+
+    def test_clamped_to_one(self):
+        self.assertEqual(bd.fill_ratio([0.8, 0.9]), 1.0)
+
+    def test_empty_is_zero(self):
+        self.assertEqual(bd.fill_ratio([]), 0.0)
+```
+
+- [ ] **Step 2: 运行确认失败**
+
+Run: `cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && python -m unittest tests.test_bl_decimate -v`
+Expected: ERROR（`module 'bl_decimate' has no attribute 'count_islands'` 等）
+
+- [ ] **Step 3: 写实现**
+
+在 `bl_decimate.py` 的 `within_tolerance` 函数之后、`# ---------------- 以下仅在 Blender 内执行` 注释之前插入：
+
+```python
+UV_BAD_TOL = 0.02   # 质量门：UV 翻转/重叠面占比超此值则回退 smart_project
+
+
+def count_islands(n_faces, adjacent_pairs):
+    """union-find 数 UV 岛：n_faces 个面，adjacent_pairs 为 UV 连续的面索引对。"""
+    parent = list(range(n_faces))
+
+    def find(i):
+        while parent[i] != i:
+            parent[i] = parent[parent[i]]
+            i = parent[i]
+        return i
+
+    for a, b in adjacent_pairs:
+        ra, rb = find(a), find(b)
+        if ra != rb:
+            parent[ra] = rb
+    return len({find(i) for i in range(n_faces)})
+
+
+def flipped_fraction(signed_areas):
+    """UV 面签名面积为负（翻转）的占比。"""
+    if not signed_areas:
+        return 0.0
+    return sum(1 for a in signed_areas if a < 0) / float(len(signed_areas))
+
+
+def fill_ratio(abs_areas):
+    """UV 空间利用率：面积和（重叠会虚高，截断到 1.0）。"""
+    return min(1.0, sum(abs_areas))
+```
+
+- [ ] **Step 4: 运行确认通过**
+
+Run: `cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && python -m unittest tests.test_bl_decimate -v`
+Expected: 19 个测试全部 PASS（原 8 + 新 11）
+
+- [ ] **Step 5: Commit**
+
+```bash
+cd "D:/UD/AI/AIC#Project" && git add Tools/ModelTranslator/bl_decimate.py Tools/ModelTranslator/tests/test_bl_decimate.py && git commit -m "ModelTranslator: UV 岛数/翻转/利用率纯逻辑（TDD）"
+```
+
+---
+
+### Task 2: seam 展开路径 + 质量门 + CLI 参数
+
+**Files:**
+- Modify: `Tools/ModelTranslator/bl_decimate.py`（Blender 区：替换 `_smart_unwrap`，`main()` 接线）
+- Modify: `Tools/ModelTranslator/model_decimate.py`（`--unwrap` + UV 指标打印）
+
+- [ ] **Step 1: bl_decimate.py 替换 `_smart_unwrap` 为新展开体系**
+
+把现有 `_smart_unwrap` 函数（`def _smart_unwrap(obj):` 到其 `bpy.ops.object.mode_set(mode='OBJECT')` 整个函数）整体替换为：
+
+```python
+SEAM_ANGLE_DEG = 66.0   # 锐边阈值：两面夹角超此值标 seam
+PACK_MARGIN = 0.002     # 岛间距 ≈ 2048 图 4px
+
+
+def _clear_uv_layers(mesh):
+    while mesh.uv_layers:
+        mesh.uv_layers.remove(mesh.uv_layers[0])
+
+
+def _unwrap_smart(obj):
+    """Smart UV Project（原路径，也是质量门的回退路径）。"""
+    import bpy
+    import math
+    _clear_uv_layers(obj.data)
+    bpy.context.view_layer.objects.active = obj
+    bpy.ops.object.mode_set(mode='EDIT')
+    bpy.ops.mesh.select_all(action='SELECT')
+    bpy.ops.uv.smart_project(angle_limit=math.radians(66.0), island_margin=PACK_MARGIN)
+    bpy.ops.object.mode_set(mode='OBJECT')
+
+
+def _unwrap_seam(obj, warnings):
+    """锐边标 seam -> MINIMUM_STRETCH/ANGLE_BASED 展开 -> pack。碎岛远少于投影式。"""
+    import bpy
+    import math
+    _clear_uv_layers(obj.data)
+    obj.data.uv_layers.new()
+    bpy.context.view_layer.objects.active = obj
+    bpy.ops.object.mode_set(mode='EDIT')
+    # 锐边标 seam：接缝只落在硬边处，平滑区域保持整岛
+    bpy.ops.mesh.select_mode(type='EDGE')
+    bpy.ops.mesh.select_all(action='DESELECT')
+    bpy.ops.mesh.edges_select_sharp(sharpness=math.radians(SEAM_ANGLE_DEG))
+    bpy.ops.mesh.mark_seam(clear=False)
+    bpy.ops.mesh.select_all(action='SELECT')
+    try:
+        bpy.ops.uv.unwrap(method='MINIMUM_STRETCH', margin=PACK_MARGIN)
+    except TypeError:  # 老版本无 SLIM 枚举
+        warnings.append("MINIMUM_STRETCH 不可用，展开改用 ANGLE_BASED")
+        bpy.ops.uv.unwrap(method='ANGLE_BASED', margin=PACK_MARGIN)
+    try:
+        bpy.ops.uv.pack_islands(rotate=True, margin=PACK_MARGIN)
+    except RuntimeError:  # headless 上下文不满足时靠 unwrap 自带打包
+        warnings.append("pack_islands 不可用，沿用 unwrap 自带布局")
+    bpy.ops.object.mode_set(mode='OBJECT')
+
+
+def _collect_uv_metrics(obj):
+    """bmesh 提取 UV 指标：岛数（UV 连续边并查集）、利用率、翻转占比、重叠占比。"""
+    import bmesh
+    bm = bmesh.new()
+    bm.from_mesh(obj.data)
+    uv = bm.loops.layers.uv.active
+    pairs = []
+    for e in bm.edges:
+        if len(e.link_faces) != 2:
+            continue
+        f1, f2 = e.link_faces
+        cont = True
+        for v in e.verts:  # 两面在该边两端 UV 一致 => UV 连续（同岛）
+            l1 = next(l for l in f1.loops if l.vert == v)
+            l2 = next(l for l in f2.loops if l.vert == v)
+            if (l1[uv].uv - l2[uv].uv).length > 1e-6:
+                cont = False
+                break
+        if cont:
+            pairs.append((f1.index, f2.index))
+    signed = []
+    for f in bm.faces:
+        area = 0.0
+        loops = f.loops
+        for i in range(len(loops)):
+            a = loops[i][uv].uv
+            b = loops[(i + 1) % len(loops)][uv].uv
+            area += a.x * b.y - b.x * a.y
+        signed.append(area * 0.5)
+    n = len(bm.faces)
+    bm.free()
+    return {"islands": count_islands(n, pairs),
+            "fill": round(fill_ratio([abs(a) for a in signed]), 4),
+            "flipped": round(flipped_fraction(signed), 4),
+            "overlap": _overlap_fraction(obj)}
+
+
+def _overlap_fraction(obj):
+    """uv.select_overlap 统计重叠 UV 面占比；op 上下文不可用返回 None。"""
+    import bpy
+    bpy.context.scene.tool_settings.use_uv_select_sync = True
+    bpy.context.view_layer.objects.active = obj
+    bpy.ops.object.mode_set(mode='EDIT')
+    bpy.ops.mesh.select_all(action='DESELECT')
+    try:
+        bpy.ops.uv.select_overlap()
+    except RuntimeError:
+        return None
+    finally:
+        bpy.ops.object.mode_set(mode='OBJECT')
+    polys = obj.data.polygons
+    if not len(polys):
+        return 0.0
+    return round(sum(1 for p in polys if p.select) / float(len(polys)), 4)
+
+
+def _do_unwrap(obj, mode, warnings):
+    """按模式展开；seam 质量不达标自动回退 smart。返回 uv 指标 dict（含 mode）。"""
+    if mode == "seam":
+        _unwrap_seam(obj, warnings)
+        m = _collect_uv_metrics(obj)
+        overlap = m["overlap"] or 0.0
+        if m["flipped"] <= UV_BAD_TOL and overlap <= UV_BAD_TOL:
+            m["mode"] = "seam"
+            return m
+        warnings.append("seam 展开质量不达标（翻转 %.1f%% 重叠 %s），回退 smart_project"
+                        % (m["flipped"] * 100,
+                           "%.1f%%" % (m["overlap"] * 100) if m["overlap"] is not None else "未知"))
+        mode = "smart_fallback"
+    _unwrap_smart(obj)
+    m = _collect_uv_metrics(obj)
+    m["mode"] = mode if mode == "smart_fallback" else "smart"
+    return m
+```
+
+- [ ] **Step 2: main() 接线（argv 第 4 参 + uv 字段）**
+
+`main()` 里两处修改。argv 解析行：
+
+```python
+    src, out_fbx, target = argv[0], argv[1], int(argv[2])
+```
+
+改为：
+
+```python
+    src, out_fbx, target = argv[0], argv[1], int(argv[2])
+    unwrap_mode = argv[3] if len(argv) > 3 else "seam"
+```
+
+`_smart_unwrap(obj)` 调用行改为：
+
+```python
+    uv_info = _do_unwrap(obj, unwrap_mode, warnings)
+```
+
+`MT_SUMMARY` 的 dict 加 `"uv": uv_info`：
+
+```python
+    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))
+```
+
+同时把文件顶部 docstring 第 1-2 行更新为：
+
+```python
+"""Blender 内运行：FBX 减面到指定三角面数 + UV 重展（锐边 seam 或 Smart UV Project）。
+调用：blender -b --factory-startup --python bl_decimate.py -- <src.fbx> <out.fbx> <target_tris> [seam|smart]
+"""
+```
+
+- [ ] **Step 3: model_decimate.py 加 --unwrap 与指标打印**
+
+argparse 增加（`--blender` 行之前）：
+
+```python
+    ap.add_argument("--unwrap", choices=("seam", "smart"), default="seam",
+                    help="UV 展开方式：seam=锐边接缝整岛展开（默认），smart=Smart UV Project")
+```
+
+`run_blender_script` 调用改为：
+
+```python
+    s = run_blender_script(blender, "bl_decimate.py",
+                           [args.input, out_fbx, str(args.tris), args.unwrap])
+```
+
+结果打印行之后、警告循环之前加：
+
+```python
+    u = s["uv"]
+    overlap = "%.1f%%" % (u["overlap"] * 100) if u["overlap"] is not None else "n/a"
+    print("  UV: 模式=%s 岛数=%d 利用率=%.1f%% 翻转=%.1f%% 重叠=%s" %
+          (u["mode"], u["islands"], u["fill"] * 100, u["flipped"] * 100, overlap))
+```
+
+文件 docstring 第 1 行的"并 Smart UV 重展"改为"并重展 UV（默认锐边 seam 整岛展开）"。
+
+- [ ] **Step 4: 语法检查 + 全部单测**
+
+Run: `cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && python -m py_compile bl_decimate.py model_decimate.py && python -m unittest discover -s tests -v`
+Expected: 编译通过，40 个测试全部 PASS（29 原有 + 11 新增）
+
+- [ ] **Step 5: Commit**
+
+```bash
+cd "D:/UD/AI/AIC#Project" && git add Tools/ModelTranslator/bl_decimate.py Tools/ModelTranslator/model_decimate.py && git commit -m "ModelTranslator: 减面 UV 改锐边 seam 展开（质量门回退 smart，--unwrap 可选）"
+```
+
+---
+
+### Task 3: 双模式冒烟对比 + README
+
+**Files:**
+- Modify: `Tools/ModelTranslator/README.md`
+- 产物 `src/well1500_low.fbx`、`/tmp` 对比数据不入 git
+
+- [ ] **Step 1: smart 模式跑基线**（timeout 300000）
+
+Run: `cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && python model_decimate.py src/well1500.fbx --tris 5000 --unwrap smart`
+Expected: 正常完成，记录 `UV: 模式=smart 岛数=N_smart 利用率=F_smart ...`
+
+- [ ] **Step 2: seam 模式（默认）跑对比**（timeout 300000）
+
+Run: `cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && python model_decimate.py src/well1500.fbx --tris 5000`
+Expected: `UV: 模式=seam ...`，且满足验收标准：
+- `岛数` 显著低于 smart 基线（至少降一个数量级或 <1/5）
+- `利用率` ≥ smart 基线的 90%
+- `翻转` ≤ 2%、`重叠` ≤ 2%（未触发回退警告）
+
+不达标则按 systematic-debugging 排查（常见点：`edges_select_sharp` 的 sharpness 语义、`MINIMUM_STRETCH` 枚举名、`pack_islands`/`select_overlap` headless poll 失败——后两者已有降级路径，看警告判断），修复后重跑并把修复单独 commit。
+
+- [ ] **Step 3: 用新低模快速复烘验证**（timeout 600000）
+
+Run: `cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && python model_bake.py src/well1500.fbx src/well1500_low.fbx --size 1024 --samples 16`
+Expected: 5 张 PNG 正常产出、无 error；用下面命令确认 normal/color 非空：
+
+```bash
+cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && "D:/tools/blender-5.0.0-windows-x64/blender.exe" -b --factory-startup --python-expr "
+import bpy
+for n in ('color', 'normal'):
+    img = bpy.data.images.load(r'D:\UD\AI\AIC#Project\Tools\ModelTranslator\out_bake\well1500\well1500_%s.png' % n)
+    uniq = len(set(round(v, 2) for v in img.pixels[:4000]))
+    print('CHECK', n, 'unique=', uniq)
+"
+```
+Expected: 两图 unique 明显 >1
+
+- [ ] **Step 4: README 更新**
+
+`README.md` 中 model_decimate.py 说明条目（"旧 UV 全删，Smart UV Project 重展"那句）改为：
+
+```
+- **model_decimate.py**：多 mesh 自动 join；三角化后 Decimate(collapse) 减到 `--tris`（±3%，最多 2 轮修正）；旧 UV 全删后重展——默认锐边标 seam + MINIMUM_STRETCH 整岛展开（碎岛少、接缝落在硬边），质量不达标（翻转/重叠 >2%）自动回退 Smart UV Project，`--unwrap smart` 可强制旧行为；输出 `<名>_low.fbx`（`-o` 改目录），日志报 UV 岛数/利用率
+```
+
+- [ ] **Step 5: 全部单测最后过一遍 + Commit**
+
+Run: `cd "D:/UD/AI/AIC#Project/Tools/ModelTranslator" && python -m unittest discover -s tests -v`
+Expected: 40/40 PASS
+
+```bash
+cd "D:/UD/AI/AIC#Project" && git add Tools/ModelTranslator/README.md && git commit -m "ModelTranslator: README 补 --unwrap 说明（well1500 双模式冒烟对比通过）"
+```
+
+- [ ] **Step 6: Unity 手动验证（用户操作）**
+
+如需上 Unity 验证：`python model_translator.py out_bake/well1500/well1500.fbx` 后拷 `out/well1500/` 进 `Client/Assets/` 查看接缝表现。此步由用户完成。