# bezierOffsetPath

Canonical: https://docs.shumoku.dev/en/library/api/bezierOffsetPath
Language: en

@shumoku/core · 0.4.0 · function

# bezierOffsetPath

[Source](https://github.com/konoe-akitoshi/shumoku/blob/main/libs/@shumoku/core/src/layout/bezier-path.ts#L124)

\`bezierEdgePath\` translated as a whole by \`offset\` SVG units along the chord-perpendicular direction. Used to draw parallel "in" / "out" lanes for weathermap-style flow overlays. This is a \*parallel translate\*, NOT a true cubic offset curve (which cannot in general be represented exactly as another cubic). All four control points shift by the same vector, so: • lane spacing is exactly \`2 \* |offset|\` everywhere along the curve, • the offset curve never crosses the base curve or the opposite lane regardless of port-side configuration (incl. same-side U-turns and adjacent-side L-turns), • tangents are preserved at every point — but the lane endpoint is shifted off the port by \`(nx, ny)\`. Lanes are decorative; they are not meant to "connect to" the port. The shift direction is the chord normal (perpendicular to b-a). Sign convention: in screen coordinates (y-down), \`+offset\` shifts to the right-hand side of the chord A→B, \`-offset\` to the left. Pass \`+offset\` and \`-offset\` for the two lanes; which one ends up labelled "in" is a data-source semantic, not enforced here. Computed analytically — no DOM measurement, so callers don't need a mounted SVGPathElement.

```
bezierOffsetPath(from: { absolutePosition: { x: number; y: number }; side?: PortSide }, to: { absolutePosition: { x: number; y: number }; side?: PortSide }, offset: number): string
```

## Parameters

| Parameter | Type | Description | Default |
| --- | --- | --- | --- |
| `from` | `{ absolutePosition: { x: number; y: number }; side?: PortSide }` | No additional description. | `—` |
| `to` | `{ absolutePosition: { x: number; y: number }; side?: PortSide }` | No additional description. | `—` |
| `offset` | `number` | No additional description. | `—` |

## Returns

```
string
```

[`libs/@shumoku/core/src/layout/bezier-path.ts:124`](https://github.com/konoe-akitoshi/shumoku/blob/main/libs/@shumoku/core/src/layout/bezier-path.ts#L124)