jarvanxing/bezier

n-degree Bezier spline interpolation.

bezier

n-degree Bezier curve interpolation.

Usage

require('bezier')(points, t)

Returns the value at t for a bezier curve of points.length degrees. In other words, if you pass it a 3-element array you'll get the results of a 3-degree (quadratic) curve.

var bezier = require('bezier')
bezier([0, 1, 2], 0.5)    // 1
bezier([0, 1, 2, 3], 0.5) // 1.5

You can use a curve for each dimension to get the resulting bezier you're probably familiar with:

var canvas = document.createElement('canvas')
var ctx = canvas.getContext('2d')

var bezier = require('bezier')
var x = [0, 100, 200]
var y = [200, 100, 0]

ctx.beginPath()
ctx.strokeStyle = '#000'
for (var t = 0; t < 1; t += 0.01) {
  ctx.lineTo(bezier(x, t), bezier(y, t))
}
ctx.stroke()
ctx.closePath()

curve = require('bezier').prepare(pointCount)

Generates a function which takes pointCount number of points to draw a bezier curve. For higher values of pointCount, this function is generated on the fly such that it can run with as little overhead as possible.

It's a small trade-off in flexibility for a small benefit in performance :)

curve(points, t)

Given an array of points that is pointCount long, return the value across the curve at t.

var quadratic = require('bezier').prepare(3)
var cubic = require('bezier').prepare(4)

quadratic([0, 1, 2], 0.5) // 1
cubic([0, 1, 2, 3], 0.5)  // 1.5

// Note that these functions expect
// arrays of the correct length:
quadratic([0, 1, 2, 3], 0.5) // 1
quadratic([0, 1], 0.5)       // NaN

License

MIT. See LICENSE.md for details.