Clean stale tuft density comment

.trellis/spec/guides/artifact-parity-guide.md

@@ -172,7 +172,6 @@ capturedAt / durationMs / label
 |---|---|---|
 | D1 | `export_cesium.py` 旧回退表 | `"Office White Metal Facade"` 四张表里都有，但 `catalog` 里已无此材质——只作为旧 `.blend` 回退兼容保留 |
 | D2 | `scene-layers.js` vs `catalog.py` | 同一批图层的颜色两侧各自手调，无一致性保证（**这是刻意的**，见[图层表](../pipeline/layer-registry.md#为什么颜色刻意不同步)） |
-| D3 | `generate_scene.py` `tuft_density_wave` | 注释仍在跟已删除的 hedge banding 作对比 |
 
 **碰到它们不要顺手修**——修复会改变产物或扩大 diff，属于独立决定。
 
@@ -189,7 +188,7 @@ capturedAt / durationMs / label
 | 一次改十个地方再跑校验 | 差异定位不到具体改动 |
 | 改 stage 打印格式 | 静默破坏契约 |
 | 摘要里保留不稳定字段 | 检查变噪音，最终被忽略 |
-| 顺手修 D1–D3 | 改变产物或扩大 diff |
+| 顺手修 D1 / D2 | 改变产物或扩大 diff |
 
 ---
 

.trellis/tasks/08-03-clean-tuft-density-comment/check.jsonl

@@ -0,0 +1,2 @@
+{"file": ".trellis/spec/blender/index.md", "reason": "Check the generate_scene.py edit remains within Blender layer constraints."}
+{"file": ".trellis/spec/guides/artifact-parity-guide.md", "reason": "Verify D3 is removed only after the stale comment is corrected."}

.trellis/tasks/08-03-clean-tuft-density-comment/implement.jsonl

@@ -0,0 +1,2 @@
+{"file": ".trellis/spec/blender/index.md", "reason": "Blender layer constraints and validation expectations for generate_scene.py changes."}
+{"file": ".trellis/spec/guides/artifact-parity-guide.md", "reason": "Contains the D3 known-defect entry and parity guidance for comment-only changes."}

.trellis/tasks/08-03-clean-tuft-density-comment/prd.md

@@ -0,0 +1,51 @@
+# Clean stale tuft density comment
+
+## Goal
+
+Clean up the documented D3 comment debt around `tuft_density_wave()` so the
+code and Trellis specs no longer reference a deleted hedge-banding comparison.
+
+This is a documentation/comment correction only. It should not change Blender
+scene generation behavior or generated artifacts.
+
+## Background
+
+- `.trellis/spec/guides/artifact-parity-guide.md` records D3:
+  `generate_scene.py` `tuft_density_wave` has a stale comment comparing lawn
+  tuft density with deleted hedge banding.
+- `blender/generate_scene.py:354` defines `tuft_density_wave(x, y)`.
+- The current function body is still valid deterministic scatter logic; only
+  the explanatory comment is stale.
+
+## Requirements
+
+1. Update the comment above `tuft_density_wave()` to describe the current lawn
+   tuft spacing intent without referencing removed hedge banding behavior.
+2. Remove or update the D3 entry in
+   `.trellis/spec/guides/artifact-parity-guide.md` so it no longer lists this
+   as an outstanding known defect after the code comment is corrected.
+3. Do not change `tuft_density_wave()` math, tuft sampling thresholds, grass
+   material behavior, object names, counts, or scene output.
+4. Do not change D1 or D2.
+5. Do not change parity ignore lists.
+
+## Acceptance Criteria
+
+- [ ] `blender/generate_scene.py` no longer has a stale hedge-banding
+      comparison near `tuft_density_wave()`.
+- [ ] `.trellis/spec/guides/artifact-parity-guide.md` no longer records D3 as
+      outstanding.
+- [ ] `python3 -m py_compile blender/generate_scene.py` passes.
+- [ ] `python3 -m unittest blender/tests/test_pure.py` passes.
+- [ ] `git diff` shows no change to `tuft_density_wave()` executable code.
+
+## Out Of Scope
+
+- Any Blender/Cesium artifact-changing behavior.
+- Full parity capture, because the task is comment/spec-only and acceptance
+  explicitly verifies no executable code changed.
+- D1 / D2 cleanup.
+
+## Open Questions
+
+None.

.trellis/tasks/08-03-clean-tuft-density-comment/task.json

@@ -0,0 +1,26 @@
+{
+  "id": "clean-tuft-density-comment",
+  "name": "clean-tuft-density-comment",
+  "title": "Clean stale tuft density comment",
+  "description": "",
+  "status": "in_progress",
+  "dev_type": null,
+  "scope": null,
+  "package": null,
+  "priority": "P2",
+  "creator": "dingkang",
+  "assignee": "dingkang",
+  "createdAt": "2026-08-03",
+  "completedAt": null,
+  "branch": null,
+  "base_branch": "main",
+  "worktree_path": null,
+  "commit": null,
+  "pr_url": null,
+  "subtasks": [],
+  "children": [],
+  "parent": null,
+  "relatedFiles": [],
+  "notes": "",
+  "meta": {}
+}