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- import { noop } from 'motion-utils';
- /*
- Bezier function generator
- This has been modified from Gaëtan Renaudeau's BezierEasing
- https://github.com/gre/bezier-easing/blob/master/src/index.js
- https://github.com/gre/bezier-easing/blob/master/LICENSE
-
- I've removed the newtonRaphsonIterate algo because in benchmarking it
- wasn't noticiably faster than binarySubdivision, indeed removing it
- usually improved times, depending on the curve.
- I also removed the lookup table, as for the added bundle size and loop we're
- only cutting ~4 or so subdivision iterations. I bumped the max iterations up
- to 12 to compensate and this still tended to be faster for no perceivable
- loss in accuracy.
- Usage
- const easeOut = cubicBezier(.17,.67,.83,.67);
- const x = easeOut(0.5); // returns 0.627...
- */
- // Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
- const calcBezier = (t, a1, a2) => (((1.0 - 3.0 * a2 + 3.0 * a1) * t + (3.0 * a2 - 6.0 * a1)) * t + 3.0 * a1) *
- t;
- const subdivisionPrecision = 0.0000001;
- const subdivisionMaxIterations = 12;
- function binarySubdivide(x, lowerBound, upperBound, mX1, mX2) {
- let currentX;
- let currentT;
- let i = 0;
- do {
- currentT = lowerBound + (upperBound - lowerBound) / 2.0;
- currentX = calcBezier(currentT, mX1, mX2) - x;
- if (currentX > 0.0) {
- upperBound = currentT;
- }
- else {
- lowerBound = currentT;
- }
- } while (Math.abs(currentX) > subdivisionPrecision &&
- ++i < subdivisionMaxIterations);
- return currentT;
- }
- function cubicBezier(mX1, mY1, mX2, mY2) {
- // If this is a linear gradient, return linear easing
- if (mX1 === mY1 && mX2 === mY2)
- return noop;
- const getTForX = (aX) => binarySubdivide(aX, 0, 1, mX1, mX2);
- // If animation is at start/end, return t without easing
- return (t) => t === 0 || t === 1 ? t : calcBezier(getTForX(t), mY1, mY2);
- }
- export { cubicBezier };
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