Keyframes in Depth

Keyframe inheritance

Keyframes always inherit missing properties from the previous keyframe. For example:

import { Rekapi, Actor } from 'rekapi';

const rekapi = new Rekapi();
const actor = rekapi.addActor();

actor.keyframe(0, {
  x: 100
}).keyframe(1000, {
  // Implicitly copies the `x: 100` from above
  y: 50

Keyframe 1000 will have a y of 50, and an x of 100, because x was inherited from keyframe 0.

Function keyframes

Instead of providing an Object to be used to interpolate state values, you can provide a function to be called at a specific point on the timeline. This function does not need to return a value, as it does not get used to render the actor state. Function keyframes are called once per animation loop and do not have any tweening relationship with one another. This is a primarily a mechanism for scheduling arbitrary code to be executed at specific points in an animation.

actor.keyframe(1000, actor => console.log(actor));


easing, if provided, can be a string or an Object. If easing is a string, all animated properties will have the same easing curve applied to them. For example:

actor.keyframe(1000, { x: 100, y: 100 }, 'easeOutSine');

Both x and y will have easeOutSine applied to them. You can also specify multiple easing curves with an Object:

actor.keyframe(1000, {
    x: 100,
    y: 100
  }, {
    x: 'easeinSine',
    y: 'easeOutSine'

x will ease with easeInSine, and y will ease with easeOutSine. Any unspecified properties will ease with linear. If easing is omitted, all properties will default to linear.