/curves-and-paths

name: curves-and-paths
description: "Use this skill when working with curves and paths in Phaser 4. Covers splines, bezier curves, lines, ellipses, path followers, and mathematical curve types. Triggers on: curve, path, spline, bezier, path follower."

Curves and Paths

> Creating paths from curves, getting points along them, drawing them with Graphics, and making sprites follow paths automatically using PathFollower in Phaser 4.

**Key source paths:** `src/curves/`, `src/curves/path/`, `src/gameobjects/pathfollower/`, `src/gameobjects/components/PathFollower.js` **Related skills:** ../sprites-and-images/SKILL.md, ../graphics-and-shapes/SKILL.md, ../tweens/SKILL.md

Quick Start

// In a Scene's create() method:

// 1. Create a Path starting at (50, 300)
const path = this.add.path(50, 300);

// 2. Add curves to the path
path.lineTo(200, 100);
path.splineTo([ new Phaser.Math.Vector2(300, 400), new Phaser.Math.Vector2(500, 200) ]);
path.lineTo(700, 300);

// 3. Draw the path using Graphics
const graphics = this.add.graphics();
graphics.lineStyle(2, 0xffffff, 1);
path.draw(graphics, 64);

// 4. Create a PathFollower sprite that moves along the path
const follower = this.add.follower(path, 50, 300, 'ship');
follower.startFollow({
    duration: 5000,
    rotateToPath: true,
    repeat: -1,
    yoyo: true
});

Core Concepts

Path

A `Phaser.Curves.Path` is a container that combines multiple Curves into one continuous compound curve. Curves in a Path do not need to be connected end-to-end. Only the order of curves affects point calculations along the path.

Created via factory: `this.add.path(x, y)` where x/y is the starting point.

Key properties:

• `curves` -- array of `Phaser.Curves.Curve` objects in the Path
• `startPoint` -- `Vector2`, the defined starting position
• `autoClose` -- boolean, if true `getPoints()` appends the first point at the end
• `defaultDivisions` -- number (default: 12), divisions per curve when calling `getPoints()`
• `name` -- string, empty by default, for developer use

Curves

All curve types extend `Phaser.Curves.Curve` (the base class). Every curve supports:

• `getPoint(t, out)` -- get a point at position t (0-1) based on curve parameterization
• `getPointAt(u, out)` -- get a point at position u (0-1) based on arc length (evenly spaced)
• `getPoints(divisions, stepRate, out)` -- array of points along the curve
• `getSpacedPoints(divisions, stepRate, out)` -- array of equidistant points by arc length
• `getDistancePoints(distance)` -- points spaced by pixel distance
• `getLength()` -- total arc length in pixels
• `getBounds(out, accuracy)` -- bounding Rectangle
• `getTangent(t, out)` / `getTangentAt(u, out)` -- unit tangent vector
• `getStartPoint(out)` / `getEndPoint(out)` -- first/last points
• `getRandomPoint(out)` -- random point on the curve
• `draw(graphics, pointsTotal)` -- render the curve onto a Graphics object
• `active` -- boolean, when false the parent Path skips this curve

PathFollower

A `Phaser.GameObjects.PathFollower` is a Sprite with the `Components.PathFollower` mixin. It uses an internal Tween (a number counter from 0 to 1) to advance along a Path each frame.

Created via factory: `this.add.follower(path, x, y, texture, frame)`

The PathFollower component provides:

• `path` -- the `Phaser.Curves.Path` being followed
• `pathTween` -- the internal Tween driving movement
• `pathOffset` -- `Vector2`, offset added to path coordinates
• `pathVector` -- `Vector2`, current position on the path
• `pathDelta` -- `Vector2`, distance traveled since last frame
• `rotateToPath` -- boolean, auto-rotate to face path direction
• `pathRotationOffset` -- number (degrees), added to auto-rotation

Common Patterns

Creating Paths with Chained Curves

Path has convenience methods that create curves starting from the previous end point:

const path = this.add.path(100, 500);

path.lineTo(300, 100);                          // straight line
path.cubicBezierTo(500, 100, 350, 50, 450, 50); // cubic bezier (endX, endY, cp1X, cp1Y, cp2X, cp2Y)
path.quadraticBezierTo(700, 400, 600, 100);     // quadratic bezier (endX, endY, cpX, cpY)
path.splineTo([                                  // spline through points
    new Phaser.Math.Vector2(750, 300),
    new Phaser.Math.Vector2(600, 500)
]);
path.ellipseTo(50, 80, 0, 270, false, 0);       // ellipse arc (xRadius, yRadius, startAngle, endAngle, clockwise, rotation)
path.circleTo(40);                               // shortcut for ellipseTo with equal radii and 0-360

// Jump to a new position without drawing (creates a gap)
path.moveTo(400, 400);
path.lineTo(500, 400);

// Close the path by connecting end to start
path.closePath();

Adding Standalone Curve Objects

const path = new Phaser.Curves.Path(0, 0);

// Add pre-constructed curve objects
const line = new Phaser.Curves.Line(new Phaser.Math.Vector2(0, 0), new Phaser.Math.Vector2(200, 200));
path.add(line);

const spline = new Phaser.Curves.Spline([ 200, 200, 300, 100, 400, 300 ]);
path.add(spline);

const ellipse = new Phaser.Curves.Ellipse(400, 300, 100, 60, 0, 360, false, 0);
path.add(ellipse);

Getting Points Along a Path

// Array of points (uses defaultDivisions per curve)
const points = path.getPoints();

// With explicit divisions per curve
const detailed = path.getPoints(32);

// Equally spaced points along the entire path
const spaced = path.getSpacedPoints(100);

// Single point at normalized position (0-1)
const midpoint = path.getPoint(0.5);

// Tangent vector at a position
const tangent = path.getTangent(0.5);

// Total path length in pixels
const length = path.getLength();

// Bounding rectangle
const bounds = path.getBounds();

Drawing Paths with Graphics

const graphics = this.add.graphics();

// Draw entire path
graphics.lineStyle(2, 0x00ff00, 1);
path.draw(graphics, 64); // 64 = points per curve for smoothness

// Draw individual curves
graphics.lineStyle(1, 0xff0000,