osmWorkflow/.trellis/tasks/08-03-extract-building-module/implement.md

Implementation Plan

Checklist

1. Capture a parity baseline before product-code edits.
2. Add blender/osmassets/building.py with the current building assembly and detail helper logic.
3. Import building.py in blender/generate_scene.py.
4. Remove inline _assemble_building() and add_building_details() from generate_scene.py.
5. Replace the building call site with building.assemble(...), passing args["office_overrides"] instead of the full args dict.
6. Run Python validation:
   • python3 -m py_compile blender/osmassets/building.py
   • python3 -m py_compile blender/generate_scene.py
   • python3 -m unittest blender/tests/test_pure.py
7. Capture parity after the refactor.
8. Compare before/after parity snapshots and inspect any non-ignored diff.
9. Update .trellis/spec and docs/changelog.md only for durable status or convention changes discovered during implementation.
10. Commit, archive the task, and record the journal entry.

Validation Commands

node scripts/parity.js capture building-module-before --stages blender,cesium
python3 -m py_compile blender/osmassets/building.py
python3 -m py_compile blender/generate_scene.py
python3 -m unittest blender/tests/test_pure.py
node scripts/parity.js capture building-module-after --stages blender,cesium
node scripts/parity.js compare building-module-before building-module-after

Risk Points

• Passing office_overrides instead of args changes the function contract; verify office_override custom properties and industrial classification via parity.
• Building_<way_id>_Windows mesh construction depends on MeshBatch object naming and add_wall_panel() geometry; copy it mechanically.
• make_prism() can return None on degenerate input, but the current call site filters len(ring) >= 3. Preserve the existing behavior and return tuple shape.
• Do not reorder building material creation or catalog entries; material order affects GLB material indices.
• Parity is mandatory because this is a pure refactor of bpy-layer scene generation.