react-spring gentle
Its stiffness is lower than default (120 against 170) and its damping is about half (14 against 26). Stiffness 120, damping 14 and mass 1 give a damping ratio of 0.639, so the spring is underdamped. It settles to within 0.1% in 0.945 s. It passes the end value by up to 7.4% at 0.373 s and crosses it 2 times.
Demo
Both boxes take 0.945 s. This is real time.
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 (945 ms) and a linear() string that follows the spring.
transition: translate 945ms linear(0, 0.0079, 0.0299, 0.0635, 0.1064, 0.1566, 0.2121, 0.2712, 0.3326, 0.395, 0.4571, 0.5181, 0.5773, 0.634, 0.6876, 0.7379, 0.7846, 0.8275, 0.8665, 0.9016, 0.9329, 0.9604, 0.9844, 1.0049, 1.0222, 1.0366, 1.0482, 1.0573, 1.0641, 1.0689, 1.0719, 1.0733, 1.0734, 1.0724, 1.0704, 1.0676, 1.0642, 1.0603, 1.0561, 1.0516, 1.0471, 1.0425, 1.038, 1.0335, 1.0292, 1.0252, 1.0213, 1.0177, 1.0144, 1.0114, 1.0087, 1.0062, 1.004, 1.0021, 1.0005, 0.9991, 0.9979, 0.9969, 0.9961, 0.9955, 0.9951, 0.9948, 0.9947, 0.9946, 0.9946, 0.9947, 0.9949, 0.9951, 0.9954, 0.9957, 0.996, 0.9963, 0.9967, 0.997, 0.9974, 0.9977, 0.998, 0.9983, 0.9985, 0.9988, 1);el.animate({ translate: ['0 0', '240px 0'] }, { duration: 945, easing: 'linear(0, 0.0079, 0.0299, 0.0635, 0.1064, 0.1566, 0.2121, 0.2712, 0.3326, 0.395, 0.4571, 0.5181, 0.5773, 0.634, 0.6876, 0.7379, 0.7846, 0.8275, 0.8665, 0.9016, 0.9329, 0.9604, 0.9844, 1.0049, 1.0222, 1.0366, 1.0482, 1.0573, 1.0641, 1.0689, 1.0719, 1.0733, 1.0734, 1.0724, 1.0704, 1.0676, 1.0642, 1.0603, 1.0561, 1.0516, 1.0471, 1.0425, 1.038, 1.0335, 1.0292, 1.0252, 1.0213, 1.0177, 1.0144, 1.0114, 1.0087, 1.0062, 1.004, 1.0021, 1.0005, 0.9991, 0.9979, 0.9969, 0.9961, 0.9955, 0.9951, 0.9948, 0.9947, 0.9946, 0.9946, 0.9947, 0.9949, 0.9951, 0.9954, 0.9957, 0.996, 0.9963, 0.9967, 0.997, 0.9974, 0.9977, 0.998, 0.9983, 0.9985, 0.9988, 1)', fill: 'both' });import { spring, springDuration, springLinear } from '../../core/motion/springs.js';
const k = 120, d = 14;
// 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: 945 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
- 120k, with mass 1
- Damping
- 14d, with mass 1
- Damping ratio
- 0.639underdamped
- Settle time
- 0.945 swithin 0.1% of the end
- Overshoot
- 7.4%peak at 0.373 s
- Crosses the end
- 2times
- 50% of travel
- 0.127 s13% of the settle time
- 90% of travel
- 0.224 s24% of the settle time
- Natural frequency
- 10.95 rad/ssqrt(k)
- Ring period
- 0.746 sone swing of the overshoot
- Peak speed
- 4.99xtimes 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
| react-spring | @react-spring/core 10.1.2 |
| config.gentle = { tension: 120, friction: 14 } | packages/core/src/constants.ts, const config |
Read it at github.com/pmndrs/react-spring/blob/main/packages/core/src/constants.ts.
Conversion: Stiffness is tension and damping is friction, with mass 1 (the default). The physics loop in the same package, acceleration = (-tension x displacement - friction x velocity) / mass, is the spring that spring() in springs.js solves.
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.