PT2

Provides a Point class that can be used to perform 2d vector operations. The Point class has convenient methods for calculating distance, magnitude (length), direction and angle (degrees and radians) to and from other Points or Point-like objects that have 'x' and 'y' properties. Also provides methods to rotate points around an optional origin.

Installing

NPM

npm i -S pt2

Yarn

yarn add pt2

Importing

var Point = require('pt2');

Babel / ES6

import Point from 'pt2';

Creating a Point

The Point constructor expects an Object with x and y properties, with each being of the type Number. If the constructor arg is omitted, or does not contain x and y properties, the x and y properties of the Point will be set to 0 (zero).

var pointA = new Point(); // {x: 0, y: 0}
var pointB = new Point({ x: 10, y: 5 }); // {x: 10, y: 5}

Setting Properties

var pointA = new Point(); // {x: 0, y: 0}
pointA.x = 10; // {x: 10, y: 0}
pointA.set({ x: 5, y: 10 }); // {x: 5: y: 10}

Cloning a Point

var pointA = new Point({ x: 1, y: 1 }); // {x: 1, y: 1}
var pointB = pointA.clone(); // {x: 1, y: 1} - a new Point is returned, not a reference to pointA

Adding and Subtracting

var pointA = new Point({ x: 1, y: 1 });
var pointB = new Point({ x: 5, y: 10 });

pointA.add(pointB); // pointA = {x: 6, y: 11}

pointB.sub(pointA); // pointB = {x: -1, y: -1}

Scaling

var pointA = new Point({ x: 1, y: 1 });
pointA.scale(10); // {x: 10, y: 10} - scales the Point in place

var pointB = pointA.scaled(10); // {x: 100, y: 100} - returns a new Point leaving pointA unaffected

Cross Product

var pointA = new Point({ x: 1, y: 1 });
var pointB = new Point({ x: 5, y: 10 });
pointA.cross(pointB); // 5

Magnitude

var pointA = new Point({ x: 1, y: 1 });
pointA.mag(); // 1.4142135623730951 - the magnitude, also referred to as the length, of the point
pointA.mag2(); // 2 - the squared magnitude of the point - similar to mag() but avoids using Math.sqrt

Normalizing

var pointA = new Point({ x: 1, y: 1 });
pointA.normalize(); // { x: 0.7071067811865475, y: 0.7071067811865475 }

var pointB = new Point({ x: 1, y: 1 });
var norm = pointB.normalized(); // new Point { x: 0.7071067811865475, y: 0.7071067811865475 } is returned - pointB is unaffected

Rotating

rotate and rotated take a value, in degrees, and an optional origin. The origin must be another Point or an Object with x and y properties. The default origin is (0, 0).

var pointA = new Point({ x: 1, y: 1 });
pointA.rotate(180); // { x: -0.9999999999897932, y: -1.0000000000102067 }

var pointB = pointA.rotated(180); // { x: 1, y: 1 } - leaves pointA unaffected

var origin = new Point({ x: 2, y: 1 });

pointA.set({ x: 1, y: 1 });
point.rotate(180, origin); // { x: 3, y: 1.0000000000102067 }

Negating

var pointA = new Point({ x: 1, y: 1 });
pointA.negate(); // {x: -1, y: -1})
var pointB = pointA.negated(); // {x: 1, y: 1} - leaves pointA unaffected

Distance Between Two Points

var pointA = new Point({ x: 1, y: 1 });
var pointB = new Point({ x: 5, y: 10 });
pointA.dist(pointB); // 9.848857801796104
pointA.dist2(pointB); // 97 - similar to dist() but avoids using Math.sqrt

Angles Between Two Points

var pointA = new Point({ x: 1, y: 1 });
var pointB = new Point({ x: 5, y: 10 });
pointA.radiansTo(pointB); // 1.1525719972156676
pointA.radiansFrom(pointB); // -1.9890206563741257
pointA.degreesTo(pointB); // 66.03751102520727
pointA.degreesFrom(pointB); // 246.03751102579207

Chaining

Most Point methods return a new Point or this so they can be chained.

var pointA = new Point({ x: 1, y: 1 });
var pointB = new Point({ x: 5, y: 5 });
pointA
  .sub(pointB)
  .normalize()
  .rotate(90)
  .scale(10);

The methods that do not return a Point or this include:

• mag
• mag2
• dist
• dist2
• radiansTo
• radiansFrom
• degreesTo
• degreesFrom