# BRIEFING — 2026-10-01T20:13:00Z

## Mission
Investigate client-side rendering architecture, isometric viewport frustum culling, procedural tile palettes for 20 TileTypes, and TileMapRenderer class contract for Milestone 2.

## 🔒 My Identity
- Archetype: teamwork_preview_explorer
- Roles: [investigation, synthesis, preview, architecture, culling math]
- Working directory: c:\Projects\FreeExile\.agents\teamwork\explorer_m2_1
- Original parent: bc45a740-aa86-45b5-8706-381960281bc6 (orchestrator_1 / af73d9ec-d3ff-4501-b986-47b632c5d073)
- Milestone: Milestone 2: Client Safe Haven Purity & Dummy Telemetry
- Milestone R2: Milestone 2: Client TileMapRenderer & Iso Culling Engine (orchestrator_11 / 1cc48fc5-ce57-4f48-8964-24cab4bfcacc)

## 🔒 Key Constraints
- Read-only investigation — do NOT implement directly in source code
- Code hygiene: monster_system.js line count limit (currently 495 lines, hard cap 500 lines)
- Target dummy telemetry isolated in target_dummy_telemetry.js <= 250 lines
- Ensure dummy immortality (dummy_primal_shrine, dummy_town_shrine) & zero loot drop / zero quest progress
- Anchor coordinate drift to originWx, originWy
- Self-contained 5-component handoff report
- Read-only investigation for Milestone 2: TileMapRenderer architecture & culling math
- tile_map_renderer.js must be <= 320 lines (soft cap 350, hard cap 500)
- World renderer (world_renderer.js) lines 12-28 terrain to be delegated cleanly without breaking props/waypoints/map device lines 29-461
- Bounding box culling formula with +2 tile safety margin based on iso_math.js

## Current Parent
- Conversation ID: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc
- Updated: 2026-10-01T20:13:00Z

## Investigation State
- **Explored paths**:
  - `client/webapp/js/engine/world_renderer.js` (lines 12–28 terrain vs lines 29–461 props/waypoints/map device)
  - `client/webapp/js/engine/iso_math.js` (2:1 isometric forward & inverse projections, frustum bounding box math)
  - `client/webapp/js/engine/tile_grid_loader.js` (binary map loading, `setTileAt` dirty chunk trigger)
  - `server/world/map_data_types.py` (all 20 `TileType` definitions, movement costs, vision blocking)
  - `tests/e2e/test_poe2_map_system_e2e.py` (81 E2E tests, 100% pass)
  - `tests/unit/test_challenger_tile_grid_stress.js` (48 unit stress tests, 100% pass)
  - `tools/lint/check_code_and_doc_hygiene.py` (clean codebase, 0 hard cap violations)
- **Key findings**:
  1. `world_renderer.js` delegation cleanly replaces lines 12–28 with `TileMapRenderer.render(ctx, camera, viewport)` and guards line 30 `vltk1_terrain` without touching lines 42–461 (map device, waypoints, loot beams).
  2. Isometric culling formula rigorously proven: $R_w = \frac{W}{128} + \frac{H}{64}$, with $+2$ tile padding giving $[minTx, maxTx]$ and $[minTy, maxTy]$.
  3. $16 \times 16$ tile chunk pre-rendering is mathematically invariant under camera translation. Single `drawImage` per chunk at `worldToIso(cx*16, cy*16) - (512, 32)` drops draw calls on mobile to 2–4 per frame.
  4. Memory budget compliance: LRU pool of 3 chunks ($1088 \times 576\text{px}$) consumes $7.17\text{ MB} \le 8.0\text{ MB}$.
  5. Full 20-TileType procedural palette table with 2.5D extrusion heights, side shadows, and edge highlights defined.
  6. Code structure for `tile_map_renderer.js` fits comfortably within ~260 lines ($\le 320$ lines target).
- **Unexplored areas**: None for M2 scope. All questions answered and verified.

## Key Decisions Made
- Maintain strict read-only explorer role.
- Complete full architecture blueprint and mathematical proof in `report.md`.
- Formulate complete 5-component `handoff.md` and update `progress.md`.

## Artifact Index
- `DISPATCH.md` — Assignment instructions
- `BRIEFING.md` — Persistent context
- `progress.md` — Liveness heartbeat
- `report.md` — In-depth architectural findings, culling math formulas, 20-tile palette matrix, and class blueprints
- `handoff.md` — Self-contained 5-component handoff report for parent orchestrator