vectors

A grab bag of vector utility functions for 2D and 3D vectors that operate on plain arrays. Much like cog, each method can be required individually to limit the amount of bloat you get from using the module on the client with browserify.

Installation

npm install vectors

Contributors

• hughsk
• shama

Usage

Each method is requireable from vectors/${method}, followed by calling the returned generator function with the number of dimensions you want your vectors to be. e.g.:

var mag = require('vectors/mag')(2)
var add = require('vectors/add')(3)
var sub = require('vectors/sub')(3)

If you want something totally generic, you can assume in most cases that appending -nd to your require will return a less performant but more flexible function:

var mag = require('vectors/mag-nd')
var add = require('vectors/add-nd')
var sub = require('vectors/sub-nd')

Most of the methods in this module support vectors of arbitrary dimensions, but the ones that don't will throw an error to let you know.

Each method takes a vec vector, which if returning a new vector will almost always do so by modifying it directly:

var spd = [+1, 0]
var acc = [-1, 0]
var cop = copy(spd)

mag(spd)      // 1
add(spd, acc) // spd === [0, 0]
mag(spd)      // 0
mag(cop)      // 1

add(vec, other[, ...])

Adds the other vector to vec:

var add = require('vectors/add')(2)
var pos = [0, 0]
var spd = [1, 1.5]

add(pos, spd)
add(pos, spd)

console.log(pos) // [2, 3]

Or add a scalar to the entire array:

var res = add([1, 1, 1], 6)
console.log(res) // [7, 7, 7]

You can disable this by passing scalars: false to the generator function for faster results:

var add = require('vectors/add')(2, { scalars: false })

copy(vec)

Returns a copy of the vector vec:

var copy = require('vectors/copy')(2)
var spd = [5, 5]

var cop = copy(spd)
mult(spd, 100) === [100, 100]
cop === [5, 5]

cross(vec, other)

Returns the cross product of vectors vec and other:

var cross = require('vectors/cross')(2)
var a = [1, 2]
var b = [8, 4]

cross(a, b) === -12

This method only works in 2 and 3 dimensions.

dist(vec, other)

Returns the distance between vectors vec and other:

var dist = require('vectors/dist')(2)
var pos1 = [2, 4]
var pos2 = [4, 4]

dist(pos1, pos2) === 2

div(vec, other[, ...])

Divides the vector vec by a other value:

var div = require('vectors/div')(2)
var spd = [5, 5]

div(spd, 2) === [2.5, 2.5]

Or divide multiple arrays from each other:

var res = div([6, 6, 6], [2, 2, 2])
console.log(res) // [3, 3, 3]

You can disable this by passing vectors: false to the generator function for faster results:

var sub = require('vectors/div')(2, { vectors: false })

dot(vec, other)

Returns the dot product of vectors vec and other:

var dot = require('vectors/dot')(2)
var vecA = [15, 5]
var vecB = [10, 8]

dot(vecA, vecB) === 190

heading(vec, other)

Mutliplies the vector vec by a scalar value:

var heading = require('vectors/heading')(2)
var a = [5, 0]
var b = [0, 5]

heading(a, b) * 180 / Math.PI === 45 // degrees

lerp(vec, start, finish, scalar)

Set vec to the linear interpolation between vectors start and finish:

var lerp = require('vectors/lerp')(2)
var start = [0, 0]
var finish = [100, 100]

lerp([], start, finish, 0.75) === [75, 75]

limit(vec, scalar)

Limits the vector vec to a magnitude of scalar units.

var limit = require('vectors/limit')(2)

limit([3, 0], 2)  === [2, 0]
limit([3, 4], 1)  === [0.6, 0.8]
limit([5, 5], 24) === [5, 5]

mag(vec)

Returns the magnitude of the vector:

var mag = require('vectors/mag')(2)
var spd = [2, 4]

mag(spd) === 4.47213595499958

mult(vec, other[, ...])

Mutliplies the vector vec by a other value:

var mult = require('vectors/mult')(2)
var spd = [5, 5]

mult(spd, 2) === [10, 10]

Or multiply multiple arrays:

var res = mult([2, 2, 2], [4, 4, 4])
console.log(res) // [8, 8, 8]

You can disable this by passing vectors: false to the generator function for faster results:

var sub = require('vectors/mult')(2, { vectors: false })

normalize(vec, scalar)

Normalizes the vector (i.e. scales it to make its distance 1 unit).

var normalize = require('vectors/normalize')(2)

normalize([3, 0])  === [1, 0]
normalize([4, 3])  === [0.8, 0.6]

sub(vec, other[, ...])

Subtracts the other vector from vec:

var sub = require('vectors/sub')(2)
var pos = [0, 0]
var spd = [1, 1.5]

sub(pos, spd)
sub(pos, spd)

console.log(pos) // [-2, -3]

Or subtract a scalar from the entire array:

var res = sub([9, 8, 7], 6)
console.log(res) // [3, 2, 1]

You can disable this by passing scalars: false to the generator function for faster results:

var sub = require('vectors/sub')(2, { scalars: false })