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feat: update architecture document with detailed project context and functional requirements for WebGL layer framework
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@ -1,5 +1,15 @@
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---
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stepsCompleted: ["step-01-init"]
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stepsCompleted:
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[
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"step-01-init",
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"step-02-context",
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"step-03-starter",
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"step-04-decisions",
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"step-05-patterns",
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"step-06-structure",
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"step-07-validation",
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"step-08-complete"
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]
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inputDocuments:
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- "_bmad-output/planning-artifacts/prd.md"
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- "_bmad-output/planning-artifacts/research/technical-WebGL-SVG-layered-rendering-research-2026-03-12.md"
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@ -8,8 +18,665 @@ workflowType: "architecture"
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project_name: "Fantasy-Map-Generator"
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user_name: "Azgaar"
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date: "2026-03-12"
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status: "complete"
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lastStep: 8
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completedAt: "2026-03-12"
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---
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# Architecture Decision Document
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# Architecture Decision Document — Fantasy-Map-Generator WebGL Layer Framework
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_This document builds collaboratively through step-by-step discovery. Sections are appended as we work through each architectural decision together._
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**Project:** Fantasy-Map-Generator
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**Author:** Azgaar (via Winston/Architect)
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**Date:** 2026-03-12
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**Status:** Complete — Ready for Implementation
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---
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## 1. Project Context Analysis
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### 1.1 Scope Summary
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This architecture addresses a **brownfield, isolated subsystem replacement** in FMG's rendering pipeline. The surface area is:
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- **New:** `WebGL2LayerFramework` TypeScript class (`src/modules/webgl-layer-framework.ts`)
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- **Refactored:** `src/renderers/draw-relief-icons.ts` — migrated to use the framework instead of ad-hoc context management
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- **Added:** Unit tests (`src/modules/webgl-layer-framework.test.ts`)
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- **Unchanged:** All 32 SVG layers, D3 data pipeline, `public/modules/` legacy JS, globe renderer, SVG export
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### 1.2 Functional Requirements Coverage
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| FR Category | Count | Architectural Component |
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| ------------------------------------ | ----- | ----------------------------------------------------------------- |
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| Framework Core (FR1–FR4) | 4 | `WebGL2LayerFramework` class |
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| Coordinate Sync (FR5–FR7) | 3 | `syncTransform()` method + orthographic camera |
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| Layer Lifecycle (FR8–FR11) | 4 | `setVisible()`, `ResizeObserver`, `dispose()` |
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| Relief Rendering (FR12–FR17) | 6 | `draw-relief-icons.ts` refactored |
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| Compatibility & Fallback (FR18–FR19) | 2 | `detectWebGL2()` guard in framework init |
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| Interaction (FR20–FR21) | 2 | `pointer-events: none` on canvas; existing Layers panel unchanged |
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| Developer API (FR22–FR24) | 3 | `register(config)` public method |
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| Testability (FR25–FR27) | 3 | Pure functions / injectable dependencies |
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**Total: 27 FRs — all addressed.**
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### 1.3 Non-Functional Constraints Shaping Architecture
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| NFR | Architectural Impact |
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| ----------------------------------------------- | ------------------------------------------------------------------------------------------- |
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| NFR-P6: No GPU teardown on hide | `setVisible(false)` must set `mesh.visible = false` only — NOT call `dispose()` |
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| NFR-C3: Max 2 WebGL contexts (1 globe + 1 map) | Single `THREE.WebGLRenderer` shared across all registered layers |
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| NFR-M3: Global Module Pattern | `window.WebGL2LayerFramework = new WebGL2LayerFrameworkClass()` at module bottom |
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| NFR-B1/B2: Bundle size ≤ 50KB gzip increase | Three.js already present; named imports only (`import { WebGLRenderer, ... } from 'three'`) |
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| NFR-M5: ≥ 80% Vitest coverage on framework core | Pure coordinate functions and registration API must be injected/mockable |
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### 1.4 Critical Brownfield Constraints Discovered in Codebase
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| Constraint | Detail | Architectural Response |
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| --------------------------------- | ------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------ |
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| Existing WebGL relief renderer | `draw-relief-icons.ts` already has a working Three.js renderer | Framework wraps/extends it — not replace from scratch |
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| `undrawRelief` tears down GPU | Current implementation disposes renderer on hide — violates NFR-P6 | Framework `setVisible(false)` replaces teardown pattern |
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| Canvas placement is wrong | Currently `insertAdjacentElement("afterend", map)` — canvas sits above all SVG layers | Framework uses positioned wrapper; MVP uses z-index above SVG (see Decision 3) |
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| Globals `viewX`, `viewY`, `scale` | Coordinate sync uses raw window globals | Framework abstracts to `syncTransform()` callable function; tests inject mock values |
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| `#map { position: absolute }` | SVG has no positioned parent container | Framework wraps SVG in `#map-container` on init |
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---
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## 2. Technology Stack
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No new dependencies are introduced. The framework uses only technologies already in the project:
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| Technology | Version | Role in This Feature |
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| ---------- | -------- | ----------------------------------------------------------- |
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| TypeScript | ^5.9.3 | Framework implementation language |
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| Three.js | ^0.183.2 | WebGL renderer, orthographic camera, scene management |
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| Vite | ^7.3.1 | Bundling (tree-shaking Three.js named imports) |
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| Vitest | ^4.0.18 | Unit tests for coordinate sync and framework API |
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| D3 | ^7.9.0 | Source of zoom transform values (`viewX`, `viewY`, `scale`) |
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**Three.js imports used (tree-shaken):**
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```typescript
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import {
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WebGLRenderer,
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Scene,
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OrthographicCamera,
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BufferGeometry,
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BufferAttribute,
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Mesh,
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MeshBasicMaterial,
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TextureLoader,
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SRGBColorSpace,
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LinearMipmapLinearFilter,
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LinearFilter,
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DoubleSide
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} from "three";
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```
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---
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## 3. Core Architectural Decisions
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### Decision 1: Single Shared WebGL Context via `WebGL2LayerFramework`
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**Decision:** A new `WebGL2LayerFrameworkClass` TypeScript module manages a single `THREE.WebGLRenderer` instance shared by all registered WebGL layers. It replaces `draw-relief-icons.ts`'s module-level renderer with a centralized framework.
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**Rationale:**
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- Browser WebGL context limit (8–16 per page) requires minimizing context creation
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- The globe renderer already holds context #1; the map framework holds context #2 — this is the budget maximum (NFR-C3)
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- A single `THREE.Scene` with `renderOrder` per layer handles draw ordering within the shared context
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- The existing `draw-relief-icons.ts` will be refactored to register with this framework instead of managing its own renderer
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**Alternatives rejected:**
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- One canvas per layer: would exceed context limit at 3+ WebGL layers
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- Raw WebGL2 without Three.js: Three.js already present; adds no bundle cost; handles context loss/restore, shader compilation, VBO management
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### Decision 2: Layer Registration API
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**Decision:** The framework exposes a `register(config: WebGLLayerConfig)` method. Callers provide an `id`, `anchorLayerId` (SVG element ID for z-position reference), `renderOrder` (Three.js scene draw order), `setup(scene)` callback, and `dispose()` callback. The framework manages canvas lifecycle; layer-specific GPU resource creation happens in `setup`.
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```typescript
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interface WebGLLayerConfig {
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id: string;
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anchorLayerId: string; // e.g. "terrain" — SVG <g> whose DOM position sets z-index
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renderOrder: number; // Three.js renderOrder for objects in this layer
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setup: (scene: THREE.Scene) => void; // called once after WebGL2 context confirmed
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dispose: (scene: THREE.Scene) => void; // called on framework.unregister(id)
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}
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```
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**What the framework manages:**
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- Canvas element creation, sizing, positioning
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- `THREE.WebGLRenderer` + `THREE.Scene` initialization
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- Z-index derivation from anchor SVG layer DOM position
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- Visibility toggle (`visible = false/true` on registered `THREE.Object3D` groups)
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- Canvas resize via `ResizeObserver`
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- D3 zoom/pan → orthographic camera sync
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**What each layer module manages:**
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- Creating `THREE.Mesh` / `BufferGeometry` / textures in `setup(scene)`
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- Clearing and rebuilding geometry when data changes (called by `drawRelief` equivalent)
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- Cleaning up GPU objects in `dispose(scene)`
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### Decision 3: Canvas Z-Index Positioning — MVP vs. Phase 2
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**MVP Decision:** The canvas is inserted as a sibling to `#map` in `#map-container` (a new `position: relative` wrapper div). The z-index is computed from the anchor SVG layer's page position in the DOM stack.
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**Known limitation:** Because all 32 SVG layers are inside `#map` (a single SVG element), CSS z-index cannot interleave the canvas between SVG layer groups. In MVP, the canvas renders **above the entire SVG** (higher z-index than `#map`). SVG layers that should visually overlay terrain icons (religion fills, borders, labels) will appear underneath the canvas.
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**Why this is acceptable for MVP:**
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- The visual impact is limited: relief icons appear in terrain cells (mountains, forests), while labels/burg icons appear in civilized cells — overlap is uncommon in practice
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- The current codebase ALREADY exhibits this same behavior (`draw-relief-icons.ts` places canvas after `#map` in DOM order with no z-index)
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- `pointer-events: none` preserves all interaction; the UX regression is purely visual
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**Phase 2 fix — DOM-Split Architecture:**
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```
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#map-container (position: relative)
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├── svg#map-back (layers 1–11, z-index: 1)
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├── canvas#terrainCanvas (z-index: 2, pointer-events: none)
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└── svg#map-front (layers 13–32 + interaction, z-index: 3)
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```
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This requires moving layer `<g>` elements between two SVG elements and syncing D3 transforms to both — deferred to Phase 2.
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**Z-index computation formula (MVP):**
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```typescript
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function getLayerZIndex(anchorLayerId: string): number {
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const anchor = document.getElementById(anchorLayerId);
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if (!anchor) return 100;
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// Use the element's index in its parent's children as the z-index base
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const siblings = Array.from(anchor.parentElement?.children ?? []);
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const idx = siblings.indexOf(anchor);
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return idx > 0 ? idx : 100;
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}
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```
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### Decision 4: D3 Zoom → WebGL Orthographic Camera Sync
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**Decision:** The sync formula from the existing `draw-relief-icons.ts` is extracted into a pure, testable function `buildCameraBounds(viewX, viewY, scale, graphWidth, graphHeight)` that returns `{left, right, top, bottom}` for the orthographic camera.
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**Derivation (documented in code):**
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```
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D3 applies transform: translate(viewX, viewY) scale(scale) to #viewbox
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This means: screen_point = map_point * scale + (viewX, viewY)
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Inverting: map_point = (screen_point - (viewX, viewY)) / scale
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Orthographic camera bounds (what map rectangle is visible on screen):
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left = -viewX / scale ← left edge of visible map
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right = (graphWidth - viewX) / scale ← right edge
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top = -viewY / scale ← top edge
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bottom = (graphHeight - viewY) / scale ← bottom edge
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Camera is configured with Y-down convention (top < bottom) to match SVG:
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new OrthographicCamera(left, right, top, bottom, -1, 1)
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where top < bottom (Y increases downward, SVG convention)
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```
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**Why this is testable:** `buildCameraBounds` takes only numbers and returns numbers. Tests inject mock `viewX/viewY/scale` values and assert exact output — no DOM or WebGL required.
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### Decision 5: Visibility Toggle — GPU State Preservation
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**Decision:** `framework.setVisible(id, visible)` toggles the Three.js `Object3D.visible` property of the layer's registered group. The canvas element's `display` style is changed only when ALL registered layers are hidden.
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```typescript
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setVisible(id: string, visible: boolean): void {
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const layer = this.layers.get(id);
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if (!layer) return;
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layer.group.visible = visible;
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// Only hide canvas if ALL layers are invisible (avoids GPU context loss)
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const anyVisible = [...this.layers.values()].some(l => l.group.visible);
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this.canvas.style.display = anyVisible ? "block" : "none";
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if (visible) this.render();
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}
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```
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**This replaces `undrawRelief`'s current behavior** which calls `renderer.dispose()`, `scene = null`, etc. — destroying GPU buffers on every hide. The framework never destroys buffers except on `framework.unregister(id)`.
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### Decision 6: WebGL2 Detection and SVG Fallback
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**Decision:** Framework initialization calls `detectWebGL2()` which attempts `canvas.getContext('webgl2')`. On failure, the framework sets a `hasFallback = true` flag and the relief renderer falls back to `drawSvg()`. All framework methods become no-ops when in fallback mode.
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```typescript
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function detectWebGL2(): boolean {
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const probe = document.createElement("canvas");
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const ctx = probe.getContext("webgl2");
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if (!ctx) return false;
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const ext = ctx.getExtension("WEBGL_lose_context");
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ext?.loseContext();
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return true;
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}
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```
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**Testable:** The detection function is exported and can be called with a mock canvas in Vitest.
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### Decision 7: Frame Rendering — On-Demand, RAF-Coalesced
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**Decision:** The framework exposes a `requestRender()` method that coalesces calls within a single animation frame, preventing redundant GPU draws during rapid pan/zoom events.
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```typescript
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private rafId: number | null = null;
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requestRender(): void {
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if (this.rafId !== null) return;
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this.rafId = requestAnimationFrame(() => {
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this.rafId = null;
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this.render();
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});
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}
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private render(): void {
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this.syncTransform();
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this.renderer.render(this.scene, this.camera);
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}
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```
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This replaces `window.rerenderReliefIcons` which currently does the same RAF coalescing at the module level.
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### Decision 8: ResizeObserver for Canvas Sizing
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**Decision:** The framework attaches a `ResizeObserver` to the `#map-container` element. On resize, it updates canvas dimensions and the orthographic camera aspect ratio, then re-renders.
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```typescript
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private observeResize(): void {
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this.resizeObserver = new ResizeObserver(entries => {
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const { width, height } = entries[0].contentRect;
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this.renderer.setSize(width, height);
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this.requestRender();
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});
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this.resizeObserver.observe(this.container);
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}
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```
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---
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## 4. Implementation Patterns
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### 4.1 Global Module Pattern (Mandatory)
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All TypeScript modules in `src/modules/` and `src/renderers/` follow the project's Global Module Pattern. The framework module must follow it exactly:
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```typescript
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// src/modules/webgl-layer-framework.ts
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// 1. Global type declaration
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declare global {
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var WebGL2LayerFramework: WebGL2LayerFrameworkClass;
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}
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// 2. Class implementation
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class WebGL2LayerFrameworkClass {
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// ...
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}
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// 3. Window registration (LAST LINE)
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window.WebGL2LayerFramework = new WebGL2LayerFrameworkClass();
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```
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### 4.2 Module Import Pattern
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Add to `src/modules/index.ts` as a side-effect import:
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```typescript
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import "./webgl-layer-framework";
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```
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And `draw-relief-icons.ts` remains in `src/renderers/index.ts` — no change to import structure.
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### 4.3 Function Naming Conventions
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| Pattern | Convention | Example |
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| ---------------------- | --------------------------- | ----------------------------------------------------- |
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| Framework class | `PascalCase + Class suffix` | `WebGL2LayerFrameworkClass` |
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| Window global | `PascalCase` | `window.WebGL2LayerFramework` |
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| Pure utility functions | `camelCase` | `buildCameraBounds`, `detectWebGL2`, `getLayerZIndex` |
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| Internal methods | `camelCase` | `syncTransform`, `observeResize`, `requestRender` |
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### 4.4 TypeScript Type Declarations
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New types go in `src/types/global.ts`:
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```typescript
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declare global {
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var WebGL2LayerFramework: import("../modules/webgl-layer-framework").WebGL2LayerFrameworkClass;
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var drawRelief: (type?: "svg" | "webGL", parentEl?: HTMLElement) => void;
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var undrawRelief: () => void;
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var rerenderReliefIcons: () => void;
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}
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```
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### 4.5 Error Handling Philosophy
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- Framework init failures (WebGL2 unavailable): set `hasFallback = true`, log with `WARN` global, no throw
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- Missing DOM elements (e.g., `#map` not found on init): early return + `WARN` log
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- WebGL context loss mid-session: `renderer.forceContextRestore()` then `renderer.dispose()` + re-init on next draw call (preserves existing pattern from `draw-relief-icons.ts`)
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- Unit tests: pure functions throw `Error`s; framework class methods log and return for resilience
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### 4.6 Test Patterns
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Unit tests co-located with source in `src/modules/`:
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```typescript
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// src/modules/webgl-layer-framework.test.ts
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import {describe, it, expect, vi} from "vitest";
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import {buildCameraBounds, detectWebGL2, getLayerZIndex} from "./webgl-layer-framework";
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describe("buildCameraBounds", () => {
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it("returns correct bounds for identity transform", () => {
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// viewX=0, viewY=0, scale=1, 960x540
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const b = buildCameraBounds(0, 0, 1, 960, 540);
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expect(b.left).toBe(0);
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expect(b.right).toBe(960);
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expect(b.top).toBe(0);
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expect(b.bottom).toBe(540);
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});
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it("returns correct bounds at 2× zoom centered on origin", () => {
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const b = buildCameraBounds(0, 0, 2, 960, 540);
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expect(b.left).toBe(0);
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expect(b.right).toBe(480);
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expect(b.top).toBe(0);
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expect(b.bottom).toBe(270);
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});
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it("returns correct bounds with pan offset", () => {
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const b = buildCameraBounds(-100, -50, 1, 960, 540);
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expect(b.left).toBe(100);
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expect(b.right).toBe(1060);
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});
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});
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describe("detectWebGL2", () => {
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it("returns false when getContext returns null", () => {
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const canvas = {getContext: () => null} as unknown as HTMLCanvasElement;
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expect(detectWebGL2(canvas)).toBe(false);
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});
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});
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```
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**Key testability rule:** Pure functions (`buildCameraBounds`, `detectWebGL2`, `getLayerZIndex`) are exported as named exports and tested without DOM/WebGL. The class itself is tested with stub canvases where needed.
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---
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## 5. Project Structure
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### 5.1 Files Created
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```
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src/
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modules/
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webgl-layer-framework.ts ← NEW: Framework class (core deliverable)
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webgl-layer-framework.test.ts ← NEW: Unit tests (≥80% coverage target)
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renderers/
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draw-relief-icons.ts ← MODIFIED: Refactored to use framework
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```
|
||||
|
||||
### 5.2 Files Modified
|
||||
|
||||
```
|
||||
src/
|
||||
modules/
|
||||
index.ts ← ADD: import "./webgl-layer-framework"
|
||||
types/
|
||||
global.ts ← ADD: WebGL2LayerFramework global declaration
|
||||
```
|
||||
|
||||
### 5.3 `webgl-layer-framework.ts` Internal Structure
|
||||
|
||||
```typescript
|
||||
// ─── Exports (for testability) ───────────────────────────────────────────────
|
||||
export function detectWebGL2(probe?: HTMLCanvasElement): boolean;
|
||||
export function buildCameraBounds(
|
||||
viewX: number,
|
||||
viewY: number,
|
||||
scale: number,
|
||||
graphWidth: number,
|
||||
graphHeight: number
|
||||
): {left: number; right: number; top: number; bottom: number};
|
||||
export function getLayerZIndex(anchorLayerId: string): number;
|
||||
|
||||
// ─── Types ───────────────────────────────────────────────────────────────────
|
||||
export interface WebGLLayerConfig {
|
||||
id: string;
|
||||
anchorLayerId: string;
|
||||
renderOrder: number;
|
||||
setup: (scene: THREE.Scene) => void;
|
||||
dispose: (scene: THREE.Scene) => void;
|
||||
}
|
||||
|
||||
interface RegisteredLayer {
|
||||
config: WebGLLayerConfig;
|
||||
group: THREE.Group;
|
||||
}
|
||||
|
||||
// ─── Class ───────────────────────────────────────────────────────────────────
|
||||
export class WebGL2LayerFrameworkClass {
|
||||
private canvas: HTMLCanvasElement | null = null;
|
||||
private renderer: THREE.WebGLRenderer | null = null;
|
||||
private camera: THREE.OrthographicCamera | null = null;
|
||||
private scene: THREE.Scene | null = null;
|
||||
private layers: Map<string, RegisteredLayer> = new Map();
|
||||
private resizeObserver: ResizeObserver | null = null;
|
||||
private rafId: number | null = null;
|
||||
private container: HTMLElement | null = null;
|
||||
readonly hasFallback: boolean = false;
|
||||
|
||||
// Public API
|
||||
init(containerId?: string): boolean;
|
||||
register(config: WebGLLayerConfig): boolean;
|
||||
unregister(id: string): void;
|
||||
setVisible(id: string, visible: boolean): void;
|
||||
requestRender(): void;
|
||||
syncTransform(): void;
|
||||
|
||||
// Private
|
||||
private render(): void;
|
||||
private observeResize(): void;
|
||||
private ensureContainer(): HTMLElement | null;
|
||||
}
|
||||
|
||||
// ─── Global Registration (MUST be last line) ─────────────────────────────────
|
||||
declare global {
|
||||
var WebGL2LayerFramework: WebGL2LayerFrameworkClass;
|
||||
}
|
||||
window.WebGL2LayerFramework = new WebGL2LayerFrameworkClass();
|
||||
```
|
||||
|
||||
### 5.4 `draw-relief-icons.ts` Refactored Structure
|
||||
|
||||
The module registers itself with the framework on load. Existing window globals (`drawRelief`, `undrawRelief`, `rerenderReliefIcons`) are preserved for backward compatibility with legacy `public/modules/` code that calls them.
|
||||
|
||||
```typescript
|
||||
// Internal: called by framework's setup callback
|
||||
function setupReliefLayer(scene: THREE.Scene): void;
|
||||
// Internal: rebuild geometry from pack.relief data
|
||||
function buildReliefScene(icons: ReliefIcon[]): void;
|
||||
// Internal: SVG fallback renderer
|
||||
function drawSvgRelief(icons: ReliefIcon[], parentEl: HTMLElement): void;
|
||||
|
||||
// Public window globals (backward-compatible)
|
||||
window.drawRelief = (type = "webGL", parentEl = byId("terrain")) => {
|
||||
if (WebGL2LayerFramework.hasFallback || type === "svg") {
|
||||
drawSvgRelief(icons, parentEl);
|
||||
} else {
|
||||
buildReliefScene(icons);
|
||||
WebGL2LayerFramework.requestRender();
|
||||
}
|
||||
};
|
||||
window.undrawRelief = () => {
|
||||
// Clears geometry but does NOT dispose GPU resources
|
||||
disposeScene(); // removes meshes from scene, keeps renderer alive
|
||||
if (terrainEl) terrainEl.innerHTML = "";
|
||||
};
|
||||
window.rerenderReliefIcons = () => {
|
||||
WebGL2LayerFramework.requestRender();
|
||||
};
|
||||
```
|
||||
|
||||
### 5.5 DOM Structure After Framework Init
|
||||
|
||||
```
|
||||
body
|
||||
div#map-container (NEW; position: relative; width: svgWidth; height: svgHeight)
|
||||
svg#map (MOVED inside container; position: absolute; inset: 0; z-index: 1)
|
||||
canvas#terrainCanvas (NEW; position: absolute; inset: 0; z-index: getLayerZIndex("terrain")+1; pointer-events: none; aria-hidden: true)
|
||||
```
|
||||
|
||||
### 5.6 Framework Initialization Sequence
|
||||
|
||||
```
|
||||
1. Framework module loaded (via src/modules/index.ts import)
|
||||
2. window.WebGL2LayerFramework = new WebGL2LayerFrameworkClass()
|
||||
→ sets hasFallback = !detectWebGL2()
|
||||
3. draw-relief-icons.ts loaded (via src/renderers/index.ts import)
|
||||
→ calls WebGL2LayerFramework.register({ id: "terrain", anchorLayerId: "terrain", ... })
|
||||
→ if hasFallback: register is a no-op, drawRelief uses SVG path
|
||||
4. Main map generation completes → window.drawRelief() called by legacy JS
|
||||
→ if WebGL: builds scene, requestRender() → next RAF → syncTransform + renderer.render
|
||||
→ if SVG fallback: drawSvgRelief()
|
||||
5. D3 zoom/pan events → window.rerenderReliefIcons() → framework.requestRender()
|
||||
6. Layer visibility toggle (legacy JS) → window.undrawRelief() or window.drawRelief()
|
||||
→ framework.setVisible("terrain", false/true) — NO GPU teardown
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## 6. Architecture Validation
|
||||
|
||||
### 6.1 FR Coverage Matrix
|
||||
|
||||
| Requirement | Addressed By | Status |
|
||||
| ---------------------------------------------- | ----------------------------------------------------------------------- | --------------------------------------------------- |
|
||||
| FR1: Single WebGL2 context | `WebGL2LayerFrameworkClass` owns one `THREE.WebGLRenderer` | ✅ |
|
||||
| FR2: Canvas at correct z-index | `getLayerZIndex(anchorLayerId)` → canvas z-index | ✅ (MVP: above SVG) |
|
||||
| FR3: Register layer by anchor + callback | `framework.register(config)` | ✅ |
|
||||
| FR4: Layer registry | `layers: Map<string, RegisteredLayer>` | ✅ |
|
||||
| FR5: Sync to D3 zoom transform | `syncTransform()` reads `viewX, viewY, scale` globals | ✅ |
|
||||
| FR6: Update on D3 change | `requestRender()` called from `rerenderReliefIcons` | ✅ |
|
||||
| FR7: Map-space → WebGL clip coordinates | `buildCameraBounds()` formula | ✅ |
|
||||
| FR8: Toggle without GPU teardown | `setVisible()` → `group.visible` only | ✅ |
|
||||
| FR9: Resize canvas on viewport change | `ResizeObserver` on container | ✅ |
|
||||
| FR10: Recalculate z-index on layer reorder | `getLayerZIndex()` reads live DOM position | ✅ |
|
||||
| FR11: Dispose layer + GPU resources | `unregister(id)` → disposes GeometryBuffers, removes from scene | ✅ |
|
||||
| FR12: All relief icons in one draw call | Per-set `Mesh` with merged `BufferGeometry` (existing batched approach) | ✅ |
|
||||
| FR13: Icons at SVG-space coordinates | Camera in SVG pixel-space; icon positions in `pack.relief` unchanged | ✅ |
|
||||
| FR14: Scale with zoom and user setting | Camera bounds change with zoom; icon size uses `r.s` from relief data | ✅ |
|
||||
| FR15: Per-icon rotation | Rotation encoded in quad vertex positions during `buildSetMesh` | ⚠️ Verify rotation support in existing buildSetMesh |
|
||||
| FR16: Configurable opacity | `MeshBasicMaterial.opacity` + `transparent: true` | ✅ |
|
||||
| FR17: Re-render on terrain data change | `drawRelief()` calls `buildReliefScene()` + `requestRender()` | ✅ |
|
||||
| FR18: WebGL2 detection + fallback | `detectWebGL2()` → `hasFallback` flag | ✅ |
|
||||
| FR19: SVG fallback visually identical | Existing `drawSvg()` preserved unchanged | ✅ |
|
||||
| FR20: No pointer-event capture | `canvas.style.pointerEvents = "none"` | ✅ |
|
||||
| FR21: Existing Layers panel unchanged | `drawRelief`/`undrawRelief` window globals preserved | ✅ |
|
||||
| FR22: Register without z-index knowledge | `framework.register` derives z-index internally | ✅ |
|
||||
| FR23: Render callback receives D3 transform | `syncTransform()` reads globals; transforms available in RAF | ✅ |
|
||||
| FR24: Same visibility API for all layers | `framework.setVisible(id, bool)` uniform for all registered layers | ✅ |
|
||||
| FR25: Coordinate sync testable in isolation | `buildCameraBounds` is a pure exported function | ✅ |
|
||||
| FR26: Fallback detection testable | `detectWebGL2(probeCanvas)` accepts injectable canvas | ✅ |
|
||||
| FR27: Registration testable without real WebGL | `hasFallback = true` path is a no-op; stub renderers in tests | ✅ |
|
||||
|
||||
**FR15 Note:** The existing `buildSetMesh` in `draw-relief-icons.ts` constructs static quads; rotation may not be applied. This must be verified and implemented (per-icon rotation via vertex transformation in `buildSetMesh`) before MVP ships.
|
||||
|
||||
### 6.2 NFR Compliance
|
||||
|
||||
| NFR | Status | Implementation |
|
||||
| ------------------------------------------ | ---------- | ----------------------------------------------------------------------------------------- |
|
||||
| NFR-P1: <16ms @ 1k icons | Enabled by | Single-batch `BufferGeometry` per atlas set |
|
||||
| NFR-P2: <100ms @ 10k icons | Enabled by | Same batch approach; measure at implementation |
|
||||
| NFR-P3: Toggle <4ms | ✅ | `group.visible = false` is O(1) |
|
||||
| NFR-P4: Pan/zoom latency <8ms | ✅ | RAF-coalesced; `syncTransform()` is one matrix update |
|
||||
| NFR-P5: Init <200ms | Enabled by | Three.js renderer init is ~50–100ms |
|
||||
| NFR-P6: No GPU teardown on hide | ✅ | `setVisible` never calls `dispose()` |
|
||||
| NFR-C1: WebGL2 as sole gate | ✅ | `detectWebGL2()` uses `canvas.getContext('webgl2')` |
|
||||
| NFR-C2: Cross-browser visual parity | Enabled by | Three.js normalizes WebGL2 across browsers |
|
||||
| NFR-C3: Max 2 contexts | ✅ | Framework creates 1 context; globe creates 1 |
|
||||
| NFR-C4: Fallback when HW accel disabled | ✅ | `detectWebGL2()` returns false → SVG path |
|
||||
| NFR-M1: Framework unknown of layer content | ✅ | `setup/dispose` callbacks encapsulate all content |
|
||||
| NFR-M2: New layer = 1 `register()` call | ✅ | Confirmed by API design |
|
||||
| NFR-M3: Global Module Pattern | ✅ | `window.WebGL2LayerFramework = new ...` at bottom |
|
||||
| NFR-M4: Sync formula documented | ✅ | `buildCameraBounds` has full derivation in JSDoc |
|
||||
| NFR-M5: ≥80% test coverage | Target | Tests for `buildCameraBounds`, `detectWebGL2`, `getLayerZIndex`, `register`, `setVisible` |
|
||||
| NFR-B1: Tree-shaking Three.js | ✅ | Named imports only |
|
||||
| NFR-B2: ≤50KB bundle increase | ✅ | No new dependencies; framework code ~5KB |
|
||||
|
||||
### 6.3 Architecture Risks and Mitigations
|
||||
|
||||
| Risk | Likelihood | Impact | Architecture Mitigation |
|
||||
| --------------------------------------------- | ---------- | ------ | ------------------------------------------------------------------------------------- |
|
||||
| D3 + WebGL coordinate offset at extreme zoom | Medium | High | `buildCameraBounds` is unit-tested at zoom 0.1–50; exact formula documented |
|
||||
| FR15: Rotation not in existing `buildSetMesh` | High | Medium | Flag as pre-MVP verification item; add rotation attribute if missing |
|
||||
| MVP z-ordering: canvas above SVG | High | Medium | Accepted tradeoff; documented; Phase 2 DOM-split design provided |
|
||||
| `undrawRelief` callers expect full cleanup | Low | Low | Preserve `undrawRelief` signature; change internals only (no GPU teardown) |
|
||||
| Context loss mid-session | Low | High | Framework inherits existing `forceContextRestore` pattern from `draw-relief-icons.ts` |
|
||||
| `will-change: transform` memory overhead | Low | Low | Apply only during active zoom/pan; remove after with timing debounce |
|
||||
|
||||
### 6.4 Decision Coherence Check
|
||||
|
||||
| Decision Pair | Compatible? | Note |
|
||||
| ------------------------------------------------------------------- | ----------- | ------------------------------------------------------------------------------ |
|
||||
| Single context (D1) + Layer registry (D2) | ✅ | `renderOrder` on `THREE.Group` within shared scene |
|
||||
| MVP z-index above SVG (D3) + pointer-events:none (D3) | ✅ | Interaction preserved regardless of z-stack |
|
||||
| Camera sync using globals (D4) + testability (FR25) | ✅ | `buildCameraBounds` is pure; globals are injected in tests |
|
||||
| No GPU teardown (D5) + `undrawRelief` backward compat (section 5.4) | ✅ | `undrawRelief` calls `disposeScene()` (geometry only) not `renderer.dispose()` |
|
||||
| On-demand RAF render (D7) + ResizeObserver (D8) | ✅ | Both call `requestRender()` which coalesces to one RAF |
|
||||
|
||||
---
|
||||
|
||||
## 7. Implementation Guidance for AI Agents
|
||||
|
||||
When implementing this architecture, follow these rules precisely:
|
||||
|
||||
### MUST DO
|
||||
|
||||
1. **Framework module registers first** — `src/modules/index.ts` import must appear before renderer imports
|
||||
2. **`window.WebGL2LayerFramework = new WebGL2LayerFrameworkClass()` is the last line** of the framework module
|
||||
3. **Export `buildCameraBounds`, `detectWebGL2`, `getLayerZIndex`** as named exports — tests depend on them
|
||||
4. **`setVisible(id, false)` NEVER calls `renderer.dispose()`** — only sets `group.visible = false`
|
||||
5. **Canvas element gets**: `pointer-events: none; aria-hidden: true; position: absolute; inset: 0`
|
||||
6. **Fallback path**: when `hasFallback === true`, all framework methods return silently; `drawRelief` calls `drawSvgRelief`
|
||||
7. **`window.drawRelief`, `window.undrawRelief`, `window.rerenderReliefIcons`** must remain as window globals (legacy JS calls them)
|
||||
8. **Verify FR15** (per-icon rotation) in `buildSetMesh` before MVP — add rotation support if missing
|
||||
|
||||
### MUST NOT DO
|
||||
|
||||
1. **Do NOT** create a second `THREE.WebGLRenderer` — framework owns the only map renderer
|
||||
2. **Do NOT** move layer `<g>` elements between SVG elements — DOM-split is Phase 2
|
||||
3. **Do NOT** add any new entries to `public/modules/` — all new code is in `src/`
|
||||
4. **Do NOT** break the `window.drawRelief(type, parentEl)` signature — legacy callers
|
||||
5. **Do NOT** use `isNaN()` — use `Number.isNaN()`; or `parseInt()` without radix
|
||||
6. **Do NOT** import Three.js as `import * as THREE from "three"` — use named imports only
|
||||
|
||||
### Verification Checklist
|
||||
|
||||
- [ ] `npm run lint` passes with zero errors
|
||||
- [ ] `npx vitest run` passes all tests
|
||||
- [ ] `buildCameraBounds` tests pass at zoom 0.1, 1, 2, 10, 50
|
||||
- [ ] `detectWebGL2` test passes with null-returning mock canvas
|
||||
- [ ] Layer registration test passes with stub scene
|
||||
- [ ] `setVisible(false)` test confirms GPU buffers remain allocated
|
||||
- [ ] Visual: relief icons render at correct coordinate positions
|
||||
- [ ] Visual: toggling terrain layer on/off preserves icon positions
|
||||
- [ ] Visual: pan/zoom redraws canvas correctly in sync with SVG
|
||||
|
||||
---
|
||||
|
||||
## 8. Next Steps
|
||||
|
||||
With this architecture complete, the recommended implementation sequence is:
|
||||
|
||||
**Story 1:** Create `webgl-layer-framework.ts` with exported pure functions and stub class methods; write all unit tests first (TDD).
|
||||
|
||||
**Story 2:** Implement `WebGL2LayerFrameworkClass` core: `init()`, `detectWebGL2()`, canvas creation, `#map-container` wrapper, `ResizeObserver`.
|
||||
|
||||
**Story 3:** Implement `register()`, `unregister()`, `setVisible()`, `requestRender()`, `syncTransform()`.
|
||||
|
||||
**Story 4:** Refactor `draw-relief-icons.ts` to use `WebGL2LayerFramework.register()` and remove the module-level renderer state. Verify FR15 rotation support.
|
||||
|
||||
**Story 5:** Integration testing — generate map, toggle terrain layer, pan/zoom, verify visual output matches SVG baseline.
|
||||
|
||||
**Story 6:** Bundle size audit — verify Three.js tree-shaking, confirm ≤50KB gzipped delta.
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue