Fantasy-Map-Generator/_bmad-output/planning-artifacts/implementation-readiness-report-2026-03-12.md

Implementation Readiness Assessment Report

Date: 2026-03-12 Project: Fantasy-Map-Generator

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Document Inventory

Document	File	Status
PRD	_bmad-output/planning-artifacts/prd.md	✅ Found (whole)
Architecture	_bmad-output/planning-artifacts/architecture.md	✅ Found (whole)
Epics & Stories	_bmad-output/planning-artifacts/epics.md	✅ Found (whole)
UX Design	—	⚠️ Not found (desktop-first tool, no UX doc — expected)

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PRD Analysis

Total FRs: 27 (FR1–FR27) Total NFRs: 17 (NFR-P1–P6, NFR-C1–C4, NFR-M1–M5, NFR-B1–B2)

PRD completeness: Complete. All requirements clearly numbered, testable, and scoped to the brownfield WebGL layer framework feature.

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Epic Coverage Validation

FR Coverage Matrix

FR	PRD Requirement (summary)	Epic / Story	Status
FR1	Single shared WebGL2 context	Epic 1 / Story 1.2	✅ Covered
FR2	Canvas at z-index derived from anchor SVG layer	Epic 1 / Story 1.2	✅ Covered
FR3	Register layer by anchor ID + render callback	Epic 1 / Story 1.3	✅ Covered
FR4	Maintain registry of all registered layers	Epic 1 / Story 1.3	✅ Covered
FR5	Sync WebGL viewport to D3 zoom transform	Epic 1 / Story 1.3	✅ Covered
FR6	Update WebGL transform on D3 zoom/pan change	Epic 1 / Story 1.3	✅ Covered
FR7	Convert map-space → WebGL clip-space coordinates	Epic 1 / Story 1.1	✅ Covered
FR8	Toggle layer visibility without GPU teardown	Epic 1 / Story 1.3	✅ Covered
FR9	Resize canvas on SVG viewport change	Epic 1 / Story 1.2	✅ Covered
FR10	Recalculate z-index on layer stack reorder	Epic 1 / Story 1.3	✅ Covered
FR11	Dispose registered layer + release GPU resources	Epic 1 / Story 1.3	✅ Covered
FR12	Render all relief icons via instanced rendering (single draw call)	Epic 2 / Story 2.2	✅ Covered
FR13	Position each relief icon at SVG-space cell coordinate	Epic 2 / Story 2.2	✅ Covered
FR14	Scale icons per zoom level and user scale setting	Epic 2 / Story 2.2	✅ Covered
FR15	Per-icon rotation from terrain dataset	Epic 2 / Stories 2.1 + 2.2	✅ Covered
FR16	Configurable opacity on relief icons	Epic 2 / Story 2.2	✅ Covered
FR17	Re-render when terrain dataset changes	Epic 2 / Story 2.2	✅ Covered
FR18	Detect WebGL2 unavailable → auto SVG fallback	Epic 1 / Story 1.2 + Epic 2 / Story 2.3	✅ Covered
FR19	SVG fallback visually identical to WebGL output	Epic 2 / Stories 2.2 + 2.3	✅ Covered
FR20	Canvas pointer-events: none — SVG layers remain interactive	Epic 2 / Story 2.2	✅ Covered
FR21	Existing Layers panel controls work unchanged	Epic 2 / Story 2.2	✅ Covered
FR22	Register new layer without z-index/lifecycle knowledge	Epic 1 / Story 1.3	✅ Covered
FR23	Render callback receives D3 transform state	Epic 1 / Story 1.3	✅ Covered
FR24	Same visibility/dispose API for all layers	Epic 1 / Story 1.3	✅ Covered
FR25	Coordinate sync testable via Vitest mock transform	Epic 1 / Story 1.1	✅ Covered
FR26	WebGL2 fallback testable via mock canvas	Epic 1 / Story 1.1 + Epic 2 / Story 2.3	✅ Covered
FR27	Registration API testable without real WebGL context	Epic 1 / Story 1.3	✅ Covered

FR Coverage: 27/27 — 100% ✅

NFR Coverage Matrix

NFR	Requirement	Story	Status
NFR-P1	<16ms @ 1k icons	Story 2.2, 3.1	✅ Covered
NFR-P2	<100ms @ 10k icons	Story 3.1	✅ Covered
NFR-P3	Toggle <4ms	Story 1.3, 3.1	✅ Covered
NFR-P4	Pan/zoom latency <8ms	Story 1.3, 3.1	✅ Covered
NFR-P5	Init <200ms	Story 1.2, 3.1	✅ Covered
NFR-P6	No GPU teardown on hide	Story 1.3, 3.1	✅ Covered
NFR-C1	WebGL2 sole gate, SVG fallback on null	Story 1.2, 2.3	✅ Covered
NFR-C2	Cross-browser visual parity	Story 2.2	✅ Covered
NFR-C3	Max 2 WebGL contexts	Story 1.2	✅ Covered
NFR-C4	Fallback when HW accel disabled	Story 2.3	✅ Covered
NFR-M1	Framework has no layer-specific knowledge	Story 1.3	✅ Covered
NFR-M2	New layer = 1 register() call	Story 1.3	✅ Covered
NFR-M3	Global Module Pattern	Story 1.2	✅ Covered
NFR-M4	Sync formula documented in code	Story 1.1	✅ Covered
NFR-M5	≥80% Vitest coverage on framework core	Story 1.1, 1.3	✅ Covered
NFR-B1	Named Three.js imports only	Story 3.2	✅ Covered
NFR-B2	≤50KB gzip bundle increase	Story 3.2	✅ Covered

NFR Coverage: 17/17 — 100% ✅

Missing Requirements: NONE

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UX Alignment Assessment

UX Document Status

Not found — expected and acceptable. This project introduces a WebGL rendering layer into a developer/worldbuilder tool. The PRD explicitly states: "No new keyboard shortcuts or UI controls are introduced by the framework itself" and "The existing layer visibility toggle is reused." The canvas element carries aria-hidden="true" (purely decorative/visual). No user-facing UI changes are in scope for this feature.

Alignment Issues

None. All user-interaction requirements (FR20, FR21) are captured in Story 2.2 with specific, testable ACs. The Layers panel is unchanged by design. pointer-events: none on the canvas is validated in Story 1.2 DOM setup.

Warnings

⚠️ Minor: If future phases (Phase 2 DOM-split, Phase 3 full GPU migration) introduce user-facing controls or new panel elements, a UX document should be created at that time. No action required for MVP.

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Epic Quality Review

Epic Structure Validation

Epic 1: WebGL Layer Framework Module

• User value: ⚠️ This is a technical foundation epic. However, for this brownfield project type, this is correct and necessary — the user value is delivered by Epic 2 (fast terrain rendering); Epic 1 is the required platform. Architecture explicitly calls this a "Platform MVP." Categorized as acceptable for this project context.
• Independence: ✅ Epic 1 stands fully alone. All three stories within it are sequentially independent.
• Brownfield indicator: ✅ No "set up from starter template" story needed — this is brownfield insertion. The framework is added to an existing codebase.

Epic 2: Relief Icons Layer Migration

• User value: ✅ Clear user outcome — worldbuilders experience fast terrain rendering with no perceived lag. Journey 1 (Katrin's dense continent) maps directly here.
• Independence: ✅ Uses Epic 1 output only. No forward dependency on Epic 3.
• Story 2.1→2.2 dependency: ✅ Correct sequence. Story 2.1 (rotation verification) is a prerequisite investigation that 2.2 builds upon — this is a valid intra-epic sequential dependency, not a forward dependency.

Epic 3: Quality & Bundle Integrity

• User value: ⚠️ No direct end-user value — these are quality gates. However, for a performance-critical feature with hard NFR targets, a dedicated validation epic is standard and warranted. The NFR targets (16ms, 100ms, 50KB) are measurable commitments.
• Independence: ✅ Epic 3 requires Epics 1+2 complete, which is the natural final phase.

Story Quality Assessment

Story Sizing

Story	Size Assessment	Verdict
1.1: Pure functions + TDD scaffold	Small — 3 pure functions + test file	✅ Well-sized
1.2: Init, canvas, DOM setup	Medium — constructor, init(), ResizeObserver, D3 zoom	✅ Well-sized
1.3: Layer lifecycle + render loop	Medium-large — 7 public methods + private render	⚠️ See note
2.1: Rotation verification	Tiny — investigation + optional fix	✅ Well-sized
2.2: Refactor draw-relief-icons.ts	Medium — register() call + 3 window globals + buildReliefScene	✅ Well-sized
2.3: Fallback verification	Small — Vitest test + visual verification	✅ Well-sized
3.1: Performance benchmarking	Small — measurement + documentation	✅ Well-sized
3.2: Bundle size audit	Small — build + analysis	✅ Well-sized

Story 1.3 note: This story covers 7 public methods (register, unregister, setVisible, clearLayer, requestRender, syncTransform, and the private render dispatch loop). This is the densest story. It is cohesive — all methods form a single logical unit (the layer management and render loop). It would be reasonable to split into 1.3a (register/unregister/setVisible/clearLayer) and 1.3b (requestRender/syncTransform/render loop) if a developer finds it too large. Not a blocker, but flagged for developer discretion.

Acceptance Criteria Quality

• ✅ All ACs use Given/When/Then BDD format
• ✅ All performance ACs include specific numeric targets (ms, percentage, KB)
• ✅ Error/fallback conditions covered (fallback path, missing DOM element, context unavailable)
• ✅ Each AC is independently verifiable
• ⚠️ Story 2.2 AC "1,000-icon map renders in <16ms" requires a real browser environment — Vitest alone cannot satisfy this AC. This is intentional (matches NFR-P1 intent) but the developer must understand this requires manual/DevTools measurement, not an automated test assertion.

Dependency Analysis

Forward Dependencies Check

• Story 1.1 → no dependencies ✅
• Story 1.2 → depends on 1.1 (uses detectWebGL2, getLayerZIndex) ✅
• Story 1.3 → depends on 1.2 (requires initialized framework) ✅
• Story 2.1 → no framework dependency (code analysis only) ✅
• Story 2.2 → depends on Epic 1 complete ✅
• Story 2.3 → depends on 2.2 (verifies the refactored module's fallback path) ✅
• Story 3.1 → depends on 2.2 complete ✅
• Story 3.2 → depends on 2.2 complete (needs built module) ✅

No forward dependencies detected. All dependency flows are downstream only.

Architecture/Brownfield Checks

• ✅ No starter template story required (brownfield — confirmed by Architecture doc)
• ✅ No "create all tables upfront" equivalent — no database, no upfront resource creation
• ✅ Window globals (drawRelief, undrawRelief, rerenderReliefIcons) backward-compatibility requirement is explicitly carried into Story 2.2 ACs
• ✅ pendingConfigs[] queue pattern (register before init) is covered in Story 1.3 — the ordering hazard is explicitly tested
• ✅ hasFallback backing-field TypeScript pattern is explicitly called out in Story 1.2 — the known compile-time footgun is documented and tested

Best Practices Compliance

Check	Status	Notes
Epics deliver user value	⚠️ Partial	Epics 1 & 3 are technical; acceptable for this platform MVP context
Epic independence	✅	Each epic functions on prior epics only
No forward dependencies	✅	Clean downstream-only dependency graph
Appropriate story sizing	✅	Story 1.3 marginally large but cohesive
ACs are testable	✅	All numeric, format-specific, verifiable
FR traceability	✅	27/27 FRs traceable to stories
Brownfield handled correctly	✅	No incorrect startup/migration stories
Architecture constraints carried into ACs	✅	backing field, canvas id, pointer-events, etc. all present

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Summary and Recommendations

Overall Readiness Status

✅ READY FOR IMPLEMENTATION

All 27 FRs and 17 NFRs are covered. No critical violations. No blocking issues.

Issues Found

Severity	Count	Items
🔴 Critical	0	—
🟠 Major	0	—
🟡 Minor	3	See below

🟡 Minor — Story 1.3 density: The 7-method scope is cohesive but large. Developer may optionally split into 1.3a (state management: register/unregister/setVisible/clearLayer) and 1.3b (render loop: requestRender/syncTransform/render dispatch). No structural change to epics required.

🟡 Minor — Story 2.2 performance AC: The <16ms render time AC requires browser DevTools measurement, not an automated Vitest assertion. Developer must not attempt to satisfy this in unit tests — it is a manual benchmark. The story AC is correct; this is a documentation awareness item.

🟡 Minor — Epic 3 user value: Stories 3.1 and 3.2 are quality gates, not user-facing features. If team velocity is a concern, these could be folded into Definition of Done criteria for Epic 2 stories rather than standalone stories. No action required unless team prefers this structure.

Recommended Next Steps

1. Begin implementation at Story 1.1 — create src/modules/webgl-layer-framework.ts with the three pure exported functions and the Vitest test file. This is pure TypeScript with zero DOM/WebGL dependencies and is the cleanest entry point.
2. Optionally split Story 1.3 into 1.3a (state management) and 1.3b (render loop) before handing off to the dev agent if the team prefers smaller units.
3. Baseline SVG render times before Story 2.2 — measure current drawRelief() timing on a 1k and 10k icon map before the refactor so the >80% improvement claim can be verified objectively in Story 3.1.
4. No UX document needed for MVP — revisit if Phase 2 (DOM-split) or Phase 3 introduce user-facing panel changes.

Final Note

This assessment identified 3 minor items across quality and sizing categories. Zero critical or major issues were found. The PRD, Architecture, and Epics documents are well-aligned, requirements are fully traced, dependencies are clean, and the brownfield integration constraints are correctly carried into acceptance criteria. The project is ready to hand off to the development agent.

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Assessment completed: 2026-03-12 — Fantasy-Map-Generator WebGL Layer Framework MVP

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