80 lines
2.9 KiB
JavaScript
80 lines
2.9 KiB
JavaScript
import { warning } from 'hey-listen';
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import { clamp } from '../../utils/clamp.mjs';
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const safeMin = 0.001;
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const minDuration = 0.01;
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const maxDuration = 10.0;
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const minDamping = 0.05;
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const maxDamping = 1;
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function findSpring({ duration = 800, bounce = 0.25, velocity = 0, mass = 1, }) {
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let envelope;
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let derivative;
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warning(duration <= maxDuration * 1000, "Spring duration must be 10 seconds or less");
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let dampingRatio = 1 - bounce;
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dampingRatio = clamp(minDamping, maxDamping, dampingRatio);
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duration = clamp(minDuration, maxDuration, duration / 1000);
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if (dampingRatio < 1) {
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envelope = (undampedFreq) => {
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const exponentialDecay = undampedFreq * dampingRatio;
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const delta = exponentialDecay * duration;
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const a = exponentialDecay - velocity;
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const b = calcAngularFreq(undampedFreq, dampingRatio);
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const c = Math.exp(-delta);
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return safeMin - (a / b) * c;
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};
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derivative = (undampedFreq) => {
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const exponentialDecay = undampedFreq * dampingRatio;
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const delta = exponentialDecay * duration;
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const d = delta * velocity + velocity;
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const e = Math.pow(dampingRatio, 2) * Math.pow(undampedFreq, 2) * duration;
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const f = Math.exp(-delta);
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const g = calcAngularFreq(Math.pow(undampedFreq, 2), dampingRatio);
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const factor = -envelope(undampedFreq) + safeMin > 0 ? -1 : 1;
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return (factor * ((d - e) * f)) / g;
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};
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}
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else {
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envelope = (undampedFreq) => {
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const a = Math.exp(-undampedFreq * duration);
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const b = (undampedFreq - velocity) * duration + 1;
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return -safeMin + a * b;
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};
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derivative = (undampedFreq) => {
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const a = Math.exp(-undampedFreq * duration);
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const b = (velocity - undampedFreq) * (duration * duration);
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return a * b;
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};
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}
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const initialGuess = 5 / duration;
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const undampedFreq = approximateRoot(envelope, derivative, initialGuess);
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duration = duration * 1000;
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if (isNaN(undampedFreq)) {
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return {
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stiffness: 100,
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damping: 10,
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duration,
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};
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}
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else {
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const stiffness = Math.pow(undampedFreq, 2) * mass;
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return {
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stiffness,
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damping: dampingRatio * 2 * Math.sqrt(mass * stiffness),
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duration,
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};
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}
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}
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const rootIterations = 12;
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function approximateRoot(envelope, derivative, initialGuess) {
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let result = initialGuess;
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for (let i = 1; i < rootIterations; i++) {
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result = result - envelope(result) / derivative(result);
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}
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return result;
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}
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function calcAngularFreq(undampedFreq, dampingRatio) {
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return undampedFreq * Math.sqrt(1 - dampingRatio * dampingRatio);
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}
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export { calcAngularFreq, findSpring, maxDamping, maxDuration, minDamping, minDuration };
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