IPO

IPO, short for InterPOlation, is an easing library allowing to describe complex easings in JSON (multiple point over time can be placed).

Inspired from Blender's IPO idea, it is made for animating a value in many ways over time.

Screenshot running example.js:

[
  { "p": [100, 100], "upper": [10, 20] },
  { "p": [200, 190], "lower": [-10, 0], "upper": [10, 0] },
  { "p": [250, 100], "upper": [30, 0] },
  { "p": [280, 140] },
  { "p": [350, 160] },
  { "p": [400, 50], "lower": [-50, 40], "upper": [100, 0] },
  { "p": [600, 250], "lower": [-140, 0], "upper": [ 40, -40 ] }
]

(the white dots are the interpolated values, the red point are the control points and their handles, the yellow curve is the SVG continuous curve.)

API

var IPO = require("ipo");
var ipo = IPO([ ...points... ]);
ipo(42); // Get the curve Y value at X=42

Format

points is:

• an Array of Point, where each Point is an object with
  • a position p which is a [x, y]
  • (option) lower: relative position of a bezier handle for the lower curve interpolation
  • (option) upper: same for the upper curve interpolation.

Under the hood

• bezier-easing is used to perform bezier interpolation. It provides efficient computation with various optimization techniques.