@loadingio/cubic v0.0.4

cubic

Calculator for cubic function and cubic bezier. Provided with an inverse function from given X to t, which could be used to calculate Y then.

Equation roots calculation use Sheng Jin Formula which might be inaccurate according to Kahan; there is an alternative solution here: https://www.npmjs.com/package/cubic-roots , which could be integrated in the future.

Usage

require! <[cubic]>
bezier = new cubic.bezier [0.2, 0.3, 0.4, 0.5]
t = Math.random!
x = bezier.x t
y = bezier.y t
t-from-x = bezier.t x

assert t == t-from-x

coff = [0 to 3].map -> Math.random!
func = new cubic.func coff.0, coff.1, coff.2, coff.3
x = Math.random!
func.calc x             # f(x)
root = func.root 0      # root for solving f(x) = 0

For a simply x -> y bezier calculation:

b = new cubic.bezier([....])
[0 to 1 by 0.1].map (x) -> y = b.y(bezier.t(x))

Compatibility

cubic use Math.cbrt which is not available in IE < 11. You can simply use a polyfill or following code:

    Math.cbrt = -> Math.pow(it, 1/3)

LICENSE

MIT