https://github.com/szymonkaliski/behaviours-rs

rust + wasm for declarative particle simulations
https://github.com/szymonkaliski/behaviours-rs

Last synced: 14 days ago
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rust + wasm for declarative particle simulations

• Host: GitHub
• URL: https://github.com/szymonkaliski/behaviours-rs
• Owner: szymonkaliski
• License: mit
• Created: 2019-06-03T14:54:17.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2023-01-07T06:02:46.000Z (almost 2 years ago)
• Last Synced: 2023-08-02T18:37:59.115Z (over 1 year ago)
• Language: Rust
• Size: 1.04 MB
• Stars: 13
• Watchers: 3
• Forks: 0
• Open Issues: 20
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
# behaviours-rs

**Work in progress!**

Rust + wasm library for declarative modeling of simple particle behaviours.

## Installation

`npm install behaviours-rs`

## Example

10000 points repelling each other:

```js

import { createSimulation } from "behaviours-rs";

const [width, height] = [600, 600];

const numPoints = 10000;

const points = new Float32Array(numPoints * 2);

for (let i = 0; i < numPoints; i++) {

  const x = Math.random() * width;

  const y = Math.random() * height;

  points[i * 2] = x;

  points[i * 2 + 1] = y;

}

// main behaviour modeling

const behaviours = [

  ["repel", { f: 0.3, r: 50.0 }],

  ["dampen", { f: 0.1 }]

];

const simulation = createSimulation(points, 2, behaviours);

const canvas = document.createElement("canvas");

canvas.width = width;

canvas.height = height;

document.body.appendChild(canvas);

const ctx = canvas.getContext("2d");

const loop = () => {

  ctx.clearRect(0, 0, 600, 600);

  simulation.step();

  const positions = simulation.get();

  for (let i = 0; i < positions.length; i += 2) {

    const x = positions[i];

    const y = positions[i + 1];

    ctx.fillRect(x, y, 1, 1);

  }

  requestAnimationFrame(loop);

};

loop();

```

Running examples:

```bash

cd ./examples/

npm install

npm start

```

## API

### Constructor

#### `const simulation = createSimulation(points, dimensions, behaviours)` - creates new simulation

- `points` - `Float32Array` of flat `x`, `y`, `z` (if in 3d) positions: `[ x1,y1,z1, x2,y2,z2, ... ]`

- `dimensions` - `2` or `3`, can be omitted, defaults to `2`

- `behaviours` - tree of behaviours

### Functions

- `simulation.step()` - single step of simulation

- `simulation.get()` - returns all positions (same format as `points` when creating simulation)

- `simulation.getIf(test)` - returns all points matching provided test (look at `"if"` behaviour)

- `simulation.setMeta(idx, key, value)` - sets additional `key`/`value` for specified point

- `simulation.getMeta(idx, key)` - returns value for provided `key` or empty string

### Behaviours

- `["repel", { f, r, p }]`

  - `f` - force, ideally between `0.0` and `1.0`

  - `r` - impact radius

  - `p` - position when the repelling happens, if ommited the points repel each other

- `["attract", { f, r, p }]`

  - `f` - force, ideally between `0.0` and `1.0`

  - `r` - impact radius

  - `p` - position when the attraction happens, if ommited the points attract each other

- `["dampen", { f }]"` - dampens velocity

  - `f` - force, ideally between `0.0` and `1.0`

- `["if", { test }, children]` - executes `children` when `test` passes

  - `test`: [`op`, `key`, `value`], where `op` is either `"==`" or `"!="`, and `key`/`value` are this point's metadata

- `["collide", { test, r }, children]` - executes `children` when points collide in given `r`, optionally passing a `test`

  - `test` - same as in `"if"`, optional

  - `r` - radius of collision

- `["set", { ke, value }]"` - sets `key`/`value` metadata on current point

For `collide` and `if` usage look into [`examples/03.js`](./examples/03.js).