https://github.com/schteppe/poly-decomp.js

Decompose 2D polygons into convex pieces.
https://github.com/schteppe/poly-decomp.js

Last synced: 10 days ago
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Decompose 2D polygons into convex pieces.

• Host: GitHub
• URL: https://github.com/schteppe/poly-decomp.js
• Owner: schteppe
• License: mit
• Created: 2013-10-12T09:31:41.000Z (about 11 years ago)
• Default Branch: master
• Last Pushed: 2023-08-08T20:14:46.000Z (over 1 year ago)
• Last Synced: 2024-10-29T20:25:13.787Z (10 days ago)
• Language: JavaScript
• Homepage: http://schteppe.github.io/poly-decomp.js/
• Size: 147 KB
• Stars: 434
• Watchers: 14
• Forks: 105
• Open Issues: 10
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-game-engine-dev - Poly-Decomp.js - Decompose 2D polygons into convex pieces. (Libraries / JavaScript)

README

        
poly-decomp.js

==============

Library for decomposing a 2D polygon into convex pieces.

![Decomposing a convcave polygon into convex regions](https://cloud.githubusercontent.com/assets/1063152/18008563/edccfe86-6ba8-11e6-9e20-a090c1812c95.gif)

[Launch the demo!](http://schteppe.github.io/poly-decomp.js/)

[![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=Z2G8VHLDJ9N3L&lc=GB&item_name=Stefan%20Hedman&item_number=schteppe&currency_code=USD&bn=PP%2dDonationsBF%3aDonate%2dPayPal%2dgreen%2esvg%3aNonHosted)

The library implements two algorithms, one optimal (but slow) and one less optimal (but fast).

It's is a manual port of the C++ library [Poly Decomp](https://mpen.ca/406/bayazit) by [Mark Penner](https://mpen.ca). 

### Install

##### Browser

Download [decomp.js](build/decomp.js) or [decomp.min.js](build/decomp.min.js) and include the script in your HTML:

```html

```

Then you can use the ```decomp``` global.

##### Node.js

```

npm install poly-decomp

```

Then require it like so:

```js

var decomp = require('poly-decomp');

```

### Basic usage

```js

// Create a concave polygon

var concavePolygon = [

  [ -1,   1],

  [ -1,   0],

  [  1,   0],

  [  1,   1],

  [0.5, 0.5]

];

// Make sure the polygon has counter-clockwise winding. Skip this step if you know it's already counter-clockwise.

decomp.makeCCW(concavePolygon);

// Decompose into convex polygons, using the faster algorithm

var convexPolygons = decomp.quickDecomp(concavePolygon);

// ==> [  [[1,0],[1,1],[0.5,0.5]],  [[0.5,0.5],[-1,1],[-1,0],[1,0]]  ]

// Decompose using the slow (but optimal) algorithm

var convexPolygons = decomp.decomp(concavePolygon);

// ==> [  [[-1,1],[-1,0],[1,0],[0.5,0.5]],  [[1,0],[1,1],[0.5,0.5]]  ]

```

### Advanced usage

```js

// Get user input as an array of points.

var polygon = getUserInput();

// Check if the polygon self-intersects

if(decomp.isSimple(polygon)){

    

    // Reverse the polygon to make sure it uses counter-clockwise winding

    decomp.makeCCW(polygon);

    

    // Decompose into convex pieces

    var convexPolygons = decomp.quickDecomp(polygon);

    

    // Draw each point on an HTML5 Canvas context

    for(var i=0; i