# regl-scatter2d [![unstable](https://img.shields.io/badge/stability-unstable-green.svg)](http://github.com/badges/stability-badges)  [![Build Status](https://img.shields.io/travis/gl-vis/regl-scatter2d.svg)](https://travis-ci.org/gl-vis/regl-scatter2d)

Fast and precise 2d scatter plot for lots of points.

![regl-scatter2d](https://github.com/gl-vis/regl-scatter2d/blob/master/preview.png?raw=true)

Remake on [gl-scatter2d](https://github.com/gl-vis/gl-scatter2d), covering other scatter-related components.

[Demo](https://gl-vis.github.io/regl-scatter2d).


## Usage

[![npm install regl-scatter2d](https://nodei.co/npm/regl-scatter2d.png?mini=true)](https://npmjs.org/package/regl-scatter2d/)

```js
let regl = require('regl')({extensions: 'oes_element_index_uint'})

let createScatter = require('regl-scatter2d')

let scatter = createScatter(regl)

//draw 5 points
scatter({
  positions: [0,0, 1,0, 2,0, 1,1, 2,1],
  color: 'rgba(0, 100, 200, .75)'
})
```

### `createScatter(regl)`

Create new scatter plot instance from `regl`. `regl` instance should have `OES_element_index_uint` extension enabled.

### `scatter(optionsA, optionsB, ...rest)`

Draw scatter points corresponding to options.

```js
// render multiple point groups
scatter(
  { points: [0,0, 1,1], color: 'blue', marker: null },
  { points: [0,1, 1,0], color: 'red', marker: someSdf }
)
```

Option | Default | Description
---|---|---
`positions`, `points` | `[]` | An array of the unrolled xy coordinates of the points as `[x,y, x,y, ...points]` or array of points `[[x,y], [x,y], ...points]`. Can be an object with `{x: [...xValues], y: [...yValues]}` planar values. For more precise memory control, like in matrix case, `x` or `y` can be an object of the form `{x: {buffer: reglBuffer, offset: value}}`, then the `reglBuffer` will be reused.
`size`, `sizes` | `12` | Number or array with marker sizes in pixels. Array length should correspond to `positions`.
`borderSize`, `borderSizes` | `1` | Number or array with border sizes in pixels. Array length should correspond to `positions`.
`color`, `colors` | `'black'` | Color or array with colors. Each color can be a css color string or an array with float `0..1` values.
`borderColor`, `borderColors` | `'transparent'` | Border color or array with border colors.
`opacity` | `1` | Regulate marker transparency separately from colors.
`marker`, `markers` | `null` | Marker SDF image, should be a rectangular array with `0..1` 1-channel values of signed distance field. Use [bitmap-sdf](https://github.com/dy/bitmap-sdf) or [svg-path-sdf](https://github.com/dy/svg-path-sdf) to generate distance array from a canvas, image or svg. `.5` value of distance corresponds to the border line. If `null`, circular marker is used.
`range`, `dataBox` | `null` | Data bounds limiting visible data as `[left, top, right, bottom]`. If `null`, the range is detected as `positions` boundaries.
`viewport`, `viewBox` | `null` | Bounding box limiting visible area within the canvas in pixels, can be an array `[left, top, right, bottom]` or an object `{left, top, right, bottom}` or `{x, y, w, h}`.
`snap` | `null` | A bool, number of points threshold to enable snapping or [point-cluster](https://github.com/plotly/point-cluster) tree instance.

### `scatter.update(optionsA, optionsB, ...rest)`

Update options corresponding to passes, not incurring redraw. Passing `null` will remove previously loaded pass.

```js
// update 3 passes
scatter.update(a, b, c)

// update 1st pass, remove 2nd pass, ignore 3rd pass
scatter.update(a, null)

// update 2nd pass (former 3rd pass)
scatter.update(null, b)

// update n-th pass
scatter.update.apply(scatter, Array.from({length: 10, 9: options}))
```

### `scatter.draw(id1|els1?, id2|els2?, ...)`

Draw groups corresponding to `id`s, optionally specify marker ids to draw via `els`:

```js
// create 3 groups of points
scatter.update(
  {points: [0,1, 1,0], color: 'red', marker: squareSdf},
  {points: [1,2, 2,1], color: 'green', marker: triangleSdf},
  {points: [0,0, 1,1], color: 'blue', marker: null}
)

// draw all groups
scatter.draw()

// draw red group
scatter.draw(0)

// draw green and blue group
scatter.draw(1, 2)

// draw the second point of the blue group and the first point of the red group
scatter.draw([1], null, [0])
```

### `scatter.destroy()`

Dispose scatter instance and associated resources.

## Related

* [regl-line2d](https://github.com/gl-vis/regl-line2d)
* [regl-error2d](https://github.com/gl-vis/regl-error2d)

## Similar

* [pts](https://github.com/williamngan/pts)

## License

© 2017 Dmitry Yv. MIT License

Development supported by [plot.ly](https://github.com/plotly/).