nvdnkpr / hull

Hull.js - JavaScript library that builds concave hull by set of points.

Examples

See live examples here.

Usage

var points = [ [236, 126], [234, 115], [238, 109], [247, 102], ... ];
hull(points, 50); // returns points of the hull (in clockwise order)

Params

• 1st param - array of coordinates in format: [[x1, y1], [x2, y2], ..., [xn, yn]];
• 2nd param - concavity. 1 - thin shape. Infinity - convex hull. By default 20.

How it works

Let's see step by step what happens when you call hull() function:

1. Hull.js takes your source points of the shape:
   
2. Builds convex hull:
   
3. After that, the edges flex inward (according to `concavity` param). For example:
   `concavity = 80` `concavity = 40` `concavity = 20`

Development

npm install # install dependencies
npm test	# build dist file and run tests

Contribute

If you want to get involved with Hull.js development, just use github flow and feel free to contribute!

To-do

• make point formats configurable to support formats like {x: 10, y: 10} and {lat: 52, lng: 82};
• add new map based example that demonstrates usage with other point formats;
• think about parallelisation of the calculations (on GPU or CPU);
• think about automatic concavity adjustment based on density.

Related papers

• Implementation of a fast and efficient concave hull algorithm;
• Computational Geometry: Convex Hulls;
• Line Segment Intersection Algorithm;
• Game Math: "Cross Product" of 2D Vectors;
• Угол между двумя векторами;
• Когда не нужна тригонометрия.

Changelog

0.2.1 — 21.10.2014

Some minor updates (doc, package.json, etc.).

0.2.0 — 20.10.2014

Second version with better performance inspired by this article.

0.1.0 — 06.09.2014

First version based on Delaunay triangulation.