chore(task): archive 08-03-use-low-poly-scrub-bush

.trellis/tasks/archive/2026-08/08-03-use-low-poly-scrub-bush/check.jsonl

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+{"_example": "Fill with {\"file\": \"<path>\", \"reason\": \"<why>\"}. Put spec/research files only — no code paths. Run `python3 .trellis/scripts/get_context.py --mode packages` to list available specs. Delete this line once real entries are added."}

.trellis/tasks/archive/2026-08/08-03-use-low-poly-scrub-bush/implement.jsonl

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+{"_example": "Fill with {\"file\": \"<path>\", \"reason\": \"<why>\"}. Put spec/research files only — no code paths. Run `python3 .trellis/scripts/get_context.py --mode packages` to list available specs. Delete this line once real entries are added."}

.trellis/tasks/archive/2026-08/08-03-use-low-poly-scrub-bush/prd.md

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+# Use low-poly scrub bush asset
+
+## Goal
+
+Prefer the new custom low-poly scrub bush asset for scrub edge instances and
+validate `nantaizi-lake-innovation-valley` Blender/Cesium/preview output.
+
+The user supplied `assets/models/custom/bush_low/bush_low.glb`. The goal is to
+test whether using it reduces scrub bush mesh cost and improves Follow
+smoothness without losing scrub ground cover or breaking material tinting.
+
+## Requirements
+
+1. Update `blender/generate_scene.py` to prefer
+   `assets/models/custom/bush_low/bush_low.glb` for scrub edge bushes.
+2. Keep `assets/models/custom/bush/bush.glb` as a fallback if the low asset is
+   missing or fails to import.
+3. Preserve deterministic scrub edge sampling and current scrub density budget:
+   `SCRUB_BUSH_SPACING = 1.8`, `SCRUB_BUSH_LIMIT_PER_PATCH = 60`.
+4. Preserve existing material tint behavior based on material names containing
+   `leaf`, `trunk`, or `twig`.
+5. Rebuild `nantaizi-lake-innovation-valley` stages `blender,cesium,preview`.
+6. Measure and report:
+   - `SCENE_DONE.scrub_bushes`
+   - GLB total nodes
+   - scrub bush node count
+   - scrub bush mesh vertex/index bytes or primitive counts from GLB digest
+   - output GLB size
+7. Do not change road/building/tree/vehicle route behavior.
+
+## Acceptance Criteria
+
+- [ ] `generate_scene.py` prefers `bush_low.glb` and falls back to `bush.glb`.
+- [ ] `python3 -m py_compile blender/generate_scene.py` passes.
+- [ ] `python3 -m unittest blender/tests/test_pure.py` passes.
+- [ ] `npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json --stages blender,cesium,preview` passes.
+- [ ] GLB digest confirms scrub bush nodes remain about `266` and scrub ground
+      metadata remains present.
+- [ ] Task report/changelog records whether `bush_low` meaningfully reduced
+      mesh cost and whether it is worth keeping.
+
+## Out Of Scope
+
+- Compressing textures or changing baked material export.
+- Replacing the preview car asset.
+- Runtime LOD implementation.
+- Further changing scrub density unless low asset validation shows it is needed.

.trellis/tasks/archive/2026-08/08-03-use-low-poly-scrub-bush/report.md

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+# Low-poly scrub bush experiment report
+
+## Outcome
+
+Do not adopt `assets/models/custom/bush_low/bush_low.glb` as the default scrub
+edge bush.
+
+The asset successfully reduced geometry cost, but user validation found the
+visual result unsatisfactory. The default generator was restored to
+`assets/models/custom/bush/bush.glb`.
+
+## Measurements
+
+Commands used during the experiment:
+
+```bash
+python3 -m py_compile blender/generate_scene.py
+python3 -m unittest blender/tests/test_pure.py
+npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json --stages blender,cesium,preview
+node scripts/glb-digest.js outputs/nantaizi-lake-innovation-valley/nantaizi-lake-innovation-valley.glb --out /tmp/nantaizi-bush-low-glb-digest.json
+node scripts/glb-digest.js assets/models/custom/bush/bush.glb --out /tmp/bush-original-digest.json
+node scripts/glb-digest.js assets/models/custom/bush_low/bush_low.glb --out /tmp/bush-low-asset-digest.json
+```
+
+Low-poly asset geometry:
+
+- Original `bush.glb`: `9.10 MB`, `63,762` vertices, `67,536` indices.
+- Experimental `bush_low.glb`: `5.79 MB`, `4,044` vertices, `4,050` indices.
+- Texture count stayed at `6`, so file size did not fall proportionally with
+  geometry.
+
+Nantaizi rebuild while using `bush_low.glb`:
+
+- `SCENE_DONE.scrub_bushes`: `266`
+- GLB nodes: `830`
+- Scrub bush nodes: `266`
+- Scrub bush shared mesh: `4,044` vertices, `4,050` indices
+- GLB size: `27.51 MB`
+- Metadata scrub polygons: `5`
+
+## Decision
+
+This proved geometry reduction works, but this particular low-poly model is not
+good enough visually. Keep the current density budget and original default bush
+asset for now. The next useful direction is a better-authored low-poly bush:
+same approximate silhouette/volume as the original, lower geometry, and reduced
+or compressed texture payload.

.trellis/tasks/archive/2026-08/08-03-use-low-poly-scrub-bush/task.json

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+{
+  "id": "use-low-poly-scrub-bush",
+  "name": "use-low-poly-scrub-bush",
+  "title": "Use low-poly scrub bush asset",
+  "description": "Prefer the new custom low-poly scrub bush asset and validate nantaizi output.",
+  "status": "completed",
+  "dev_type": null,
+  "scope": null,
+  "package": null,
+  "priority": "P2",
+  "creator": "dingkang",
+  "assignee": "dingkang",
+  "createdAt": "2026-08-03",
+  "completedAt": "2026-08-03",
+  "branch": null,
+  "base_branch": "main",
+  "worktree_path": null,
+  "commit": null,
+  "pr_url": null,
+  "subtasks": [],
+  "children": [],
+  "parent": null,
+  "relatedFiles": [],
+  "notes": "",
+  "meta": {}
+}