name: geometry-and-math

description: "Use this skill when using Phaser 4 math and geometry utilities. Covers vectors, rectangles, circles, triangles, polygons, random number generation, angles, distance, interpolation, and snapping. Triggers on: Vector2, Rectangle, Circle, math, distance, angle, random, lerp."

Phaser 4 — Geometry and Math

Geom classes (Circle, Ellipse, Line, Polygon, Rectangle, Triangle), intersection tests, and Math utilities (Vector2, Vector3, Matrix4, angles, distances, interpolation, easing, random, snap, clamp).

Related skills: graphics-and-shapes.md, physics-arcade.md

Quick Start

// Create geometry objects (these are data only, not renderable)
const rect = new Phaser.Geom.Rectangle(10, 20, 200, 100);
const circle = new Phaser.Geom.Circle(400, 300, 50);
const line = new Phaser.Geom.Line(0, 0, 100, 100);

// Point containment
rect.contains(50, 50);    // true
circle.contains(410, 310); // true

// Intersection test
Phaser.Geom.Intersects.CircleToRectangle(circle, rect); // boolean

// Math utilities
const v = new Phaser.Math.Vector2(3, 4);
v.length();      // 5
v.normalize();   // {x: 0.6, y: 0.8}

const dist = Phaser.Math.Distance.Between(0, 0, 100, 100);
const angle = Phaser.Math.Angle.Between(0, 0, 100, 100);
const clamped = Phaser.Math.Clamp(150, 0, 100); // 100

Core Concepts

Geometry objects are pure data containers holding coordinates and dimensions. They are NOT game objects and cannot be added to the display list. To render geometry, use the Graphics game object or Shape game objects (see graphics-and-shapes.md).

Every geom class has a type property set to a Phaser.Geom constant for fast type checks.

All geom classes share a common instance method pattern:

• contains(x, y) -- point-in-shape test
• getPoint(position, output?) -- point at normalized position (0-1) on perimeter
• getPoints(quantity, stepRate?, output?) -- evenly spaced points on perimeter
• getRandomPoint(output?) -- random point inside the shape
• setTo(...) -- reset all properties
• setEmpty() -- zero out the shape
• setPosition(x, y) -- move origin/center

Each geom type also has a folder of static helper functions (e.g., Phaser.Geom.Rectangle.Contains, Phaser.Geom.Circle.Area).

Geometry Classes

Rectangle Static Helpers

Phaser.Geom.Rectangle.*: Area, Ceil, CeilAll, CenterOn, Clone, Contains, ContainsPoint, ContainsRect, CopyFrom, Decompose, Equals, FitInside, FitOutside, Floor, FloorAll, FromPoints, FromXY, GetAspectRatio, GetCenter, GetPoint, GetPoints, GetSize, Inflate, Intersection, MarchingAnts, MergePoints, MergeRect, MergeXY, Offset, OffsetPoint, Overlaps, Perimeter, PerimeterPoint, Random, RandomOutside, SameDimensions, Scale, Union.

Circle Static Helpers

Phaser.Geom.Circle.*: Area, Circumference, CircumferencePoint, Clone, Contains, ContainsPoint, ContainsRect, CopyFrom, Equals, GetBounds, GetPoint, GetPoints, Offset, OffsetPoint, Random.

Line Static Helpers

Phaser.Geom.Line.*: Angle, BresenhamPoints, CenterOn, Clone, CopyFrom, Equals, Extend, GetEasedPoints, GetMidPoint, GetNearestPoint, GetNormal, GetPoint, GetPoints, GetShortestDistance, Height, Length, NormalAngle, NormalX, NormalY, Offset, PerpSlope, Random, ReflectAngle, Rotate, RotateAroundPoint, RotateAroundXY, SetToAngle, Slope, Width.

Triangle Static Helpers

Phaser.Geom.Triangle.*: Area, BuildEquilateral, BuildFromPolygon, BuildRight, CenterOn, Centroid, CircumCenter, CircumCircle, Clone, Contains, ContainsArray, ContainsPoint, CopyFrom, Decompose, Equals, GetPoint, GetPoints, InCenter, Offset, Perimeter, Random, Rotate, RotateAroundPoint, RotateAroundXY.

Polygon Input Formats

The Polygon constructor accepts multiple formats for the points argument:

• Space-separated string: '40 0 40 20 100 20 100 80'
• Array of {x, y} objects
• Flat number array: [x1, y1, x2, y2, ...]
• Array of [x, y] sub-arrays

Intersection Tests

All under Phaser.Geom.Intersects.

Boolean Tests (return true/false)