# Beams

Shafts of light from a point that fade with distance.

## Installation

```sh
pnpm add astro-dither
```

Or copy the source into your project:

```sh
npx astro-dither add effect
```

## Usage

```astro
---
import { DitherEffect } from "astro-dither";
---

<DitherEffect effect="beams" />
```

Noise-streaked rays fan out from `cx`, `cy`. `fade` controls how quickly they die out, so high values give short candlelight rays and low values let the beams cross the whole surface.

The props group like this:

Placement: `cx`, `cy`. Falloff: `fade`.

## Examples

### Edge light

A centre above the box makes rays drop like stage lights.

```astro
<DitherEffect effect="beams" params={{"cx":0.5,"cy":-0.2,"fade":0.8}} />
```

### Short shimmer

High `fade` pins the light close to its source.

```astro
<DitherEffect effect="beams" params={{"cx":0.5,"cy":0.5,"fade":4}} />
```

## Props

| Prop | Type | Default | Description |
| --- | --- | --- | --- |
| `cx` | `number` | 0.5 | Source x, 0 to 1. 0 to 1. |
| `cy` | `number` | 1.15 | Source y, can sit off the surface. 0 to 2. |
| `fade` | `number` | 1.6 | How quickly the rays die out. 0.2 to 5. |
| `palette` | `string[]` | the effect's | 2 to 8 colours, paper first, brightest last. `transparent` works. |
| `cell` | `number` | 2 | Size of one dither cell in CSS pixels. Rounded to whole device pixels so cells stay even. |
| `matrix` | `2 | 4 | 8 | "noise"` | 8 | The Bayer threshold size, or noise for a random look. |
| `speed` | `number` | 1 | Playback speed. 0 draws one still frame. |
| `stillTime` | `number` | the effect's | The moment drawn when motion is off or reduced, in seconds. |
| `levels` | `number` | 0 (all) | Tones the field snaps to before dithering. Low values give hard, posterised steps. |
| `bloom` | `number` | 0 | Bloom around lit cells, 0 to 1. Set a positive prop to create the overlay before overriding it with CSS `--dither-bloom`. |
| `bloomRadius` | `number` | 10 | Bloom blur in CSS pixels. CSS `--dither-bloom-radius` overrides it. |
| `class` | `string` | undefined | Classes on the surface element, for size and position. |

## Notes

* Decorative and `aria-hidden`. Put real text on top, not inside it.
* With reduced motion it draws one still frame (at 4s) and stops.
* It pauses when scrolled out of view or when the tab is hidden.
* Shares one WebGL context with every other ordered effect on the page.