---
title: "Chained path notation"
package: "@phaser-ae/path-notation"
tier: Free
version: 3.0.0-0
released: 2026-10-19
updated: 2026-10-19
description: "Routes written as plain data, a start point and a chain of lines, beziers, arcs, spirals and waves, baked so followers move at an even speed."
url: https://phaser.io/packs/path-notation
site: Phaser - https://phaser.io
---

# Chained path notation

A route authored as data: a start point and a chain of segments, each picking up where the last left off. Enemy attack
runs, patrol routes and racing lines live in a level file or a wave table instead of in code, and move at an even
speed once baked.

## What it does

A path is written as `{ start, segments }`. Each segment is one shape continuing from the current point: a `line` to a
point, a `quad` or `cubic` bezier, an `arc` round a centre to an angle (going past 360 degrees keeps orbiting, and a
second radius makes it an ellipse), a `spiral` whose radius glides to a new size over a number of turns, or a `wave`
that rides a straight chord while swinging to either side as a sine or a zigzag. Each segment can carry its own ease,
and the whole run can have one too, so an enemy can dawdle in and then whip round a loop.

`new Path(data)` bakes the route once into arc-length tables. After that, `getPoint(t)` gives the place a fraction of
the way along by length and `getAngle(t)` the direction of travel, cheap enough for hundreds of followers to call every
frame, and `getPoint` can reuse an object you pass so nothing is allocated. `Path.fromJSON` takes a JSON string or the
data.

The bake can transform the authored coordinates. `flipX` mirrors every x about a vertical line, `flipY` every y about a
horizontal one, and `offset` moves the whole route, so one attack run written for the left of the screen serves the
right as well, and offset copies let a formation fly one route side by side.

## Features

- **Six segment kinds** — lines, quadratic and cubic beziers, elliptical arcs, spirals and sine or zigzag waves.
- **Chained** — each segment starts where the last ended, so routes read like directions.
- **Eases per segment and per run** — any named easing from the maths pack, or your own function.
- **Plain JSON** — for level files, config tables and wave plans.
- **Mirror and move** — `flipX`, `flipY` and `offset`, applied once at the bake.
- **Even speed** — arc-length tables, with the sample count per segment yours to raise.
- **Fast queries** — `getPoint` and `getAngle` for many followers every frame.

## Good for

- **Shoot-'em-ups**, with enemy attack runs that loop and swoop, in the style of 1942 or Gradius, mirrored for each side
  of the screen.
- **Wave tables and level files** that need routes as data alongside spawn times and enemy types.
- **Patrol routes** for guards and creatures, written once and reused.
- **Racing lines** for computer opponents on a circuit.
- **Cut-scene moves** where a character or camera follows a set route.

## Make it yours

The route is the data, so changing a level means editing JSON. Each `Path` also takes `flipX`, `flipY`, `offset` and
`samplesPerSegment` (48 by default; more for long or tight segments). Two different uses: a shooter whose wave table
holds one attack run, baked twice, once as written and once with `flipX` at the centre of the screen, so enemies peel
in from both sides; and a racing game whose computer cars follow a closed circuit of arcs and lines read from the
track's level file.

## A quick look

An attack run of a line, an eased arc and a wave, baked as written and mirrored:

```ts
import { Path } from '@phaser-ae/path-notation';
const run = { start: [-40, 80], segments: [
    { line: [200, 80] },
    { arc: { center: [200, 160], to: 450 }, ease: 'easeInOutSine' },
    { wave: { to: [520, 300], amplitude: 30, cycles: 3 } },
] };
const fromLeft = new Path(run), fromRight = new Path(run, { flipX: W / 2 });
const p = fromLeft.getPoint(t);
```

## Works with

- `track` — networks of routes with junctions, built from this notation.
- `scrolling-shooter` — shooter rules whose enemy routes are written in it.
- `track-racer` — racing rules whose circuits are built from it.
- `path` — moves an object along a single geometry shape, without authoring a chain.
- `path-3d` — for curves in 3D with frames.

## Good to know

- It is 2D only.
- A segment is sampled into short straight pieces, so between samples a point lies on the chord; raise
  `samplesPerSegment` for long, tight curves.
- Eases change where `t` lands, so an eased route is no longer even in speed.
- It computes places and angles; moving objects along the route is your game's, or a pack built on it.

---

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