Motion scale default
The source calls it criticallyDampedSpring, but damping 30 is below critical for stiffness 550, which is 2 x sqrt(550), about 46.9. Motion uses that value only when a scale animates to 0. Stiffness 550, damping 30 and mass 1 give a damping ratio of 0.64, so the spring is underdamped. It settles to within 0.1% in 0.445 s. It passes the end value by up to 7.3% at 0.174 s and crosses it 2 times.
Demo
Both boxes take 0.445 s. Playing at 0.5× speed.
Your system asks for reduced motion, so nothing plays. The chart shows the whole move.
Code
A spring has no fixed duration, so the CSS takes the settle time (445 ms) and a linear() string that follows the spring.
transition: translate 445ms linear(0, 0.008, 0.0304, 0.0645, 0.1079, 0.1587, 0.2148, 0.2746, 0.3366, 0.3994, 0.4619, 0.5233, 0.5827, 0.6395, 0.6932, 0.7435, 0.79, 0.8327, 0.8714, 0.9062, 0.9372, 0.9643, 0.9878, 1.0079, 1.0248, 1.0387, 1.0499, 1.0586, 1.065, 1.0694, 1.0721, 1.0732, 1.073, 1.0717, 1.0694, 1.0665, 1.0629, 1.0589, 1.0546, 1.0501, 1.0455, 1.0409, 1.0364, 1.032, 1.0277, 1.0237, 1.02, 1.0165, 1.0132, 1.0103, 1.0077, 1.0053, 1.0032, 1.0014, 0.9999, 0.9986, 0.9975, 0.9966, 0.9959, 0.9954, 0.995, 0.9948, 0.9947, 0.9946, 0.9947, 0.9949, 0.9951, 0.9953, 0.9956, 0.9959, 0.9962, 0.9966, 0.9969, 0.9972, 0.9976, 0.9979, 0.9982, 0.9984, 0.9987, 0.999, 1);el.animate({ translate: ['0 0', '240px 0'] }, { duration: 445, easing: 'linear(0, 0.008, 0.0304, 0.0645, 0.1079, 0.1587, 0.2148, 0.2746, 0.3366, 0.3994, 0.4619, 0.5233, 0.5827, 0.6395, 0.6932, 0.7435, 0.79, 0.8327, 0.8714, 0.9062, 0.9372, 0.9643, 0.9878, 1.0079, 1.0248, 1.0387, 1.0499, 1.0586, 1.065, 1.0694, 1.0721, 1.0732, 1.073, 1.0717, 1.0694, 1.0665, 1.0629, 1.0589, 1.0546, 1.0501, 1.0455, 1.0409, 1.0364, 1.032, 1.0277, 1.0237, 1.02, 1.0165, 1.0132, 1.0103, 1.0077, 1.0053, 1.0032, 1.0014, 0.9999, 0.9986, 0.9975, 0.9966, 0.9959, 0.9954, 0.995, 0.9948, 0.9947, 0.9946, 0.9947, 0.9949, 0.9951, 0.9953, 0.9956, 0.9959, 0.9962, 0.9966, 0.9969, 0.9972, 0.9976, 0.9979, 0.9982, 0.9984, 0.9987, 0.999, 1)', fill: 'both' });import { spring, springDuration, springLinear } from '../../core/motion/springs.js';
const k = 550, d = 30;
// per-frame code (window.seek, vawe.onFrame): t is seconds since the move starts
const x = 240 * spring(t, k, d);
// CSS and Web Animations: 445 ms, the linear() string above
el.animate(
{ translate: ['0 0', '240px 0'] },
{ duration: springDuration(k, d) * 1000, easing: springLinear(k, d), fill: 'both' },
);Numbers
- Stiffness
- 550k, with mass 1
- Damping
- 30d, with mass 1
- Damping ratio
- 0.64underdamped
- Settle time
- 0.445 swithin 0.1% of the end
- Overshoot
- 7.3%peak at 0.174 s
- Crosses the end
- 2times
- 50% of travel
- 0.06 s13% of the settle time
- 90% of travel
- 0.105 s24% of the settle time
- Natural frequency
- 23.45 rad/ssqrt(k)
- Ring period
- 0.349 sone swing of the overshoot
- Peak speed
- 5.02xtimes the average speed
- linear() points
- 81within 0.19% of travel
Computed with spring() and springDuration() from core/motion/springs.js. The settle time is the last moment the spring is more than 0.1% away from the end value; a library stops its own spring by its own rest thresholds, so its clock can run shorter.
Source of the numbers
| Motion (Framer Motion) | motion-dom 14.9.0 (motion and framer-motion 14.9.0) |
| criticallyDampedSpring(target) = { type: "spring", stiffness: 550, damping: target === 0 ? 2 * Math.sqrt(550) : 30, restSpeed: 10 } | criticallyDampedSpring in animation/utils/default-transitions.ts |
Read it at github.com/motiondivision/motion/blob/main/packages/motion-dom/src/animation/utils/default-transitions.ts.
Conversion: Stiffness and damping are used as they are, with mass 1.
Related springs
The four closest curves in this set, by the average gap between the two springs over their first seconds. A gap of 0.01 is invisible; 0.1 is a different feel.