@urban-toolkit/autk-core

---

@urban-toolkit/autk-core / offsetPolyline

Function: offsetPolyline()

offsetPolyline(points, distance): [number, number][]

Defined in: utils-geometry.ts:30

Builds a closed polygon buffer around a polyline for stroke rendering.

Input coordinates are expected to already be in a local planar system. Consecutive duplicate points are skipped before the offset is computed. The returned polygon includes a repeated closing vertex and is suitable for triangulation with earcut.

Parameters

points

number[][]

Ordered local-space polyline coordinates.

distance

number

Offset distance applied on both sides of the polyline.

Returns

[number, number][]

A closed polygon describing the buffered polyline footprint in local planar coordinates. Returns an empty array when the input contains fewer than two distinct points or when distance is 0.

Throws

Never throws. Degenerate inputs return an empty array rather than raising an error.

Example

const poly = offsetPolyline([[0, 0], [10, 0], [10, 10]], 2);
// poly is a closed ring e.g. [[-0, 2], [10, -2], [12, 10], …]