# Phase 3 Task 3.2: Edge LOD Implementation Complete

**Status:** ✅ Completed
**Date:** 2026-01-31
**Estimated Time:** 3 hours
**Actual Time:** ~30 minutes

## Overview

Successfully integrated Edge Level of Detail (LOD) rendering in the FlowGraphViewInner component to progressively reduce edge complexity based on distance from viewport center.

## Changes Made

### File Modified

**`/Users/kooshapari/temp-PRODVERCEL/485/kush/trace/frontend/apps/web/src/components/graph/FlowGraphViewInner.tsx`**

### 1. Added Edge LOD Import

Added import for the `getEdgeLODTier` function:

```typescript
import { getEdgeLODTier } from '@/lib/edgeLOD';
```

### 2. Updated `initialEdges` useMemo

Integrated edge LOD tier calculation into the edge rendering pipeline:

```typescript
const initialEdges = useMemo((): Edge[] => {
  const viewport = getViewport?.() ?? { x: 0, y: 0, zoom: 1 };
  const viewportCenter = {
    x: viewport.x + window.innerWidth / 2 / viewport.zoom,
    y: viewport.y + window.innerHeight / 2 / viewport.zoom,
  };

  const maxAnimatedEdges = 20;
  const animatedEdgeIds = new Set(
    edgesForRendering
      .filter((link) => link.type === 'depends_on' || link.type === 'blocks')
      .slice(0, maxAnimatedEdges)
      .map((link) => link.id),
  );

  return edgesForRendering
    .map((link) => {
      const cached = getCachedEdgeStyle(link.type);

      const sourceNode = dagreLaidoutNodes.find((n) => n.id === link.sourceId);
      const targetNode = dagreLaidoutNodes.find((n) => n.id === link.targetId);
      if (!sourceNode || !targetNode) return null;

      const edgeMidpoint = {
        x: (sourceNode.position.x + targetNode.position.x) / 2,
        y: (sourceNode.position.y + targetNode.position.y) / 2,
      };

      const lodTier = getEdgeLODTier(edgeMidpoint, viewportCenter, viewport.zoom);
      if (lodTier.level === 'hidden') return null;

      return {
        id: link.id,
        source: link.sourceId,
        target: link.targetId,
        type: lodTier.pathType === 'bezier' ? 'smoothstep' : 'default',
        animated: lodTier.level === 'detailed' && animatedEdgeIds.has(link.id),
        style: {
          ...cached.style,
          strokeWidth: lodTier.strokeWidth,
          opacity: lodTier.opacity,
        },
        ...(lodTier.showLabel && {
          label: cached.label,
          labelStyle: cached.labelStyle,
          labelBgStyle: EDGE_LABEL_BG_STYLE,
        }),
        ...(lodTier.showArrow && cached.markerEnd && { markerEnd: cached.markerEnd }),
      };
    })
    .filter(Boolean) as Edge[];
}, [edgesForRendering, dagreLaidoutNodes, getViewport]);
```

## Implementation Details

### Edge LOD Tier System

The implementation uses a 4-tier LOD system defined in `/lib/edgeLOD.ts`:

1. **Detailed** (distance < 300): Full detail with bezier paths, labels, arrows, 2px width, 100% opacity
2. **Medium** (300-600): Bezier paths, no labels, arrows, 1.5px width, 80% opacity
3. **Simple** (600-1200): Straight paths, no labels/arrows, 1px width, 50% opacity
4. **Hidden** (>1200): Edges are filtered out entirely

### Key Features

- **Distance-based LOD**: Edges far from viewport center are simplified or hidden
- **Zoom-aware**: LOD thresholds adjust based on zoom level
- **Animation control**: Only detailed edges can be animated
- **Path type switching**: Bezier curves for close edges, straight lines for distant ones
- **Progressive opacity**: Edges fade as they move away from focus
- **Conditional rendering**: Labels and arrows only shown when appropriate

### Performance Benefits

- **Reduced GPU load**: Fewer complex bezier curves to render
- **Lower memory usage**: Hidden edges not rendered at all
- **Improved FPS**: Simplified edges require less computation
- **Better visual clarity**: Reduces clutter in complex graphs

## Dependencies

- Relies on existing `edgeLOD.ts` module
- Uses `dagreLaidoutNodes` for edge endpoint positions
- Integrates with `getViewport` from ReactFlow
- Works with existing edge caching system

## Testing Notes

- Edge LOD tiers should transition smoothly as viewport moves
- Animation should only appear on detailed edges
- Labels should disappear at medium and simple LOD levels
- Edges beyond 1200 distance should be completely hidden
- Zoom changes should affect LOD tier thresholds

## Related Files

- `/lib/edgeLOD.ts` - LOD tier definitions and calculation
- `/components/graph/FlowGraphViewInner.tsx` - Main implementation
- `/lib/enhancedViewportCulling.ts` - Complementary culling system

## Next Steps

- Monitor performance metrics in production
- Consider adding user-configurable LOD thresholds
- Add visual indicators for LOD tier transitions (if needed)
- Integrate with performance monitoring dashboard
