@woosh/meep-engine/src/core/math/smootherStep.js

Pure JavaScript game engine. Fully featured and production ready.

import { clamp01 } from "./clamp01.js";

/**
 * Ken Perlin's suggested improvement on `smoothStep` function
 * has gentler entry and exit slope
 * @see https://en.wikipedia.org/wiki/Smoothstep
 * @param {number} edge0
 * @param {number} edge1
 * @param {number} x
 * @returns {number}
 */
export function smootherStep(edge0, edge1, x) {
    // Scale, and clamp x to 0..1 range
    const span = edge1 - edge0;

    const t = clamp01((x - edge0) / span);

    return t * t * t * (t * (6.0 * t - 15.0) + 10.0);
}