# 
[](https://www.npmjs.com/package/@thi.ng/ramp)
[](https://mastodon.thi.ng/@toxi)
> [!NOTE]
> This is one of 214 standalone projects, maintained as part
> of the [@thi.ng/umbrella](https://codeberg.org/thi.ng/umbrella/) ecosystem
> and anti-framework.
>
> 🚀 Please help me to work full-time on these projects by [sponsoring
> me](https://codeberg.org/thi.ng/umbrella/src/branch/develop/CONTRIBUTING.md#donations).
> Thank you! ❤️
- [About](#about)
- [Status](#status)
- [Installation](#installation)
- [Dependencies](#dependencies)
- [Usage examples](#usage-examples)
- [API](#api)
- [Numeric](#numeric)
- [nD vectors](#nd-vectors)
- [Nested objects](#nested-objects)
- [Grouped & nested ramps](#grouped--nested-ramps)
- [Authors](#authors)
- [License](#license)
## About
Extensible keyframe interpolation/tweening of arbitrary, nested types.
This package can perform keyframe interpolation for ramps of numeric values,
n-dimensional vectors and nested objects of the same. It provides several
interpolation methods out of the box, but can be extended by implementing a
simple interface to achieve other interpolation methods.
Built-in interpolation modes:
- [linear](https://docs.thi.ng/umbrella/ramp/functions/linear.html)
- [cubic hermite](https://docs.thi.ng/umbrella/ramp/functions/hermite.html)
- [arbitrary easing functions](https://docs.thi.ng/umbrella/ramp/functions/easing.html)
## Status
**STABLE** - used in production
[Search or submit any issues for this package](https://codeberg.org/thi.ng/umbrella/issues?q=%5Bramp%5D)
## Installation
```bash
yarn add @thi.ng/ramp
```
ESM import:
```ts
import * as ramp from "@thi.ng/ramp";
```
Browser ESM import:
```html
```
[JSDelivr documentation](https://www.jsdelivr.com/)
For Node.js REPL:
```js
const ramp = await import("@thi.ng/ramp");
```
Package sizes (brotli'd, pre-treeshake): ESM: 2.02 KB
## Dependencies
- [@thi.ng/api](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/api)
- [@thi.ng/arrays](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/arrays)
- [@thi.ng/compare](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/compare)
- [@thi.ng/errors](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/errors)
- [@thi.ng/math](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/math)
- [@thi.ng/transducers](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/transducers)
- [@thi.ng/vectors](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/vectors)
Note: @thi.ng/api is in _most_ cases a type-only import (not used at runtime)
## Usage examples
Two projects in this repo's
[/examples](https://codeberg.org/thi.ng/umbrella/src/branch/develop/examples)
directory are using this package:
| Screenshot | Description | Live demo | Source |
|:------------------------------------------------------------------------------------------------------------------------|:---------------------------------------------------------|:-------------------------------------------------------|:--------------------------------------------------------------------------------------------|
| 
| Scroll-based, reactive, multi-param CSS animation basics | [Demo](https://demo.thi.ng/umbrella/ramp-scroll-anim/) | [Source](https://codeberg.org/thi.ng/umbrella/src/branch/develop/examples/ramp-scroll-anim) |
| 
| Unison wavetable synth with waveform editor | [Demo](https://demo.thi.ng/umbrella/ramp-synth/) | [Source](https://codeberg.org/thi.ng/umbrella/src/branch/develop/examples/ramp-synth) |
## API
[Generated API docs](https://docs.thi.ng/umbrella/ramp/)
### Numeric
```ts tangle:export/readme.ts
import { linear, hermite, easing } from "@thi.ng/ramp";
const stops = [[0.1, 0], [0.5, 1], [0.9, 0]];
const rampL = linear(stops);
const rampH = hermite(stops);
const rampE = easing(stops);
for(let i = 0; i <= 10; i++) {
const t = i / 10;
console.log(t, rampL.at(t).toFixed(3), rampH.at(t).toFixed(3), rampE.at(t).toFixed(3));
}
// 0 0.000 0.000 0.000
// 0.1 0.000 0.000 0.000
// 0.2 0.250 0.156 0.016
// 0.3 0.500 0.500 0.500
// 0.4 0.750 0.844 0.984
// 0.5 1.000 1.000 1.000
// 0.6 0.750 0.844 0.984
// 0.7 0.500 0.500 0.500
// 0.8 0.250 0.156 0.016
// 0.9 0.000 0.000 0.000
// 1 0.000 0.000 0.000
```
### nD vectors
```ts tangle:export/readme-vector.ts
import { HERMITE_V, VEC3, ramp } from "@thi.ng/ramp";
import { FORMATTER } from "@thi.ng/vectors";
// use the generic `ramp()` factory function with a custom implementation
// see: https://docs.thi.ng/umbrella/ramp/interfaces/RampImpl.html
const rgb = ramp(
// use a vector interpolation preset with the VEC3 API
HERMITE_V(VEC3),
// keyframes
[
[0.0, [1, 0, 0]], // red
[0.5, [0, 1, 0]], // green
[1.0, [0, 0, 1]], // blue
]
);
for (let i = 0; i <= 20; i++) {
const t = i / 20;
console.log(t, FORMATTER(rgb.at(t)));
}
// 0 [1.000, 0.000, 0.000]
// 0.05 [0.972, 0.028, 0.000]
// 0.1 [0.896, 0.104, 0.000]
// 0.15 [0.784, 0.216, 0.000]
// 0.2 [0.648, 0.352, 0.000]
// 0.25 [0.500, 0.500, 0.000]
// 0.3 [0.352, 0.648, 0.000]
// 0.35 [0.216, 0.784, 0.000]
// 0.4 [0.104, 0.896, 0.000]
// 0.45 [0.028, 0.972, 0.000]
// 0.5 [0.000, 1.000, 0.000]
// 0.55 [0.000, 0.972, 0.028]
// 0.6 [0.000, 0.896, 0.104]
// 0.65 [0.000, 0.784, 0.216]
// 0.7 [0.000, 0.648, 0.352]
// 0.75 [0.000, 0.500, 0.500]
// 0.8 [0.000, 0.352, 0.648]
// 0.85 [0.000, 0.216, 0.784]
// 0.9 [0.000, 0.104, 0.896]
// 0.95 [0.000, 0.028, 0.972]
// 1 [0.000, 0.000, 1.000]
```
### Nested objects
```ts tangle:export/readme-nested.ts
import { HERMITE_V, LINEAR_N, VEC2, nested, ramp } from "@thi.ng/ramp";
const r = ramp(
nested({
a: LINEAR_N,
b: nested({
c: HERMITE_V(VEC2),
}),
}),
[
[0, { a: 0, b: { c: [100, 100] } }],
[0.5, { a: 10, b: { c: [300, 50] } }],
[1, { a: -10, b: { c: [200, 120] } }],
]
);
// produce an iterator of N uniformly spaced sample points
// across the full range of the ramp
console.log([...r.samples(10)]);
// [
// [0, { a: 0, b: { c: [100, 100] } }],
// [0.1, { a: 2, b: { c: [120.8, 94.8] } }],
// [0.2, { a: 4, b: { c: [170.4, 82.4] } }],
// [0.3, { a: 6, b: { c: [229.6, 67.6] } }],
// [0.4, { a: 8, b: { c: [279.2, 55.2] } }],
// [0.5, { a: 10, b: { c: [300, 50] } }],
// [0.6, { a: 6, b: { c: [289.6, 57.28] } }],
// [0.7, { a: 2, b: { c: [264.8, 74.64] } }],
// [0.8, { a: -2, b: { c: [235.2, 95.36] } }],
// [0.9, { a: -6, b: { c: [210.4, 112.72] } }],
// [1, { a: -10, b: { c: [200, 120] } }]
// ]
```
### Grouped & nested ramps
```ts tangle:export/readme-group.ts
import { group, linear, wrap } from "@thi.ng/ramp";
const example = group({
// child timeline with looping behavior
a: linear([[0, 0], [20, 100]], { domain: wrap }),
// another child timeline
b: linear([[10, 100], [90, 200]]),
});
console.log(JSON.stringify([...example.samples(10, 0, 100)]));
// [
// [0, { a: 0, b: 100 }],
// [10, { a: 50, b: 100 }],
// [20, { a: 100, b: 112.5 }],
// [30, { a: 50, b: 125 }],
// [40, { a: 100, b: 137.5 }],
// [50, { a: 50, b: 150 }],
// [60, { a: 0, b: 162.5 }],
// [70, { a: 50, b: 175 }],
// [80, { a: 0, b: 187.5 }],
// [90, { a: 50, b: 200 }],
// [100, { a: 50, b: 200 }]
// ]
```
## Authors
- [Karsten Schmidt](https://thi.ng)
If this project contributes to an academic publication, please cite it as:
```bibtex
@misc{thing-ramp,
title = "@thi.ng/ramp",
author = "Karsten Schmidt",
note = "https://thi.ng/ramp",
year = 2019
}
```
## License
© 2019 - 2026 Karsten Schmidt // Apache License 2.0