README.md

Liang-Barsky line-clipping algorithm

Fast, destructive implemetation of Liang-Barsky line clipping algorithm. It clips a 2D segment by a rectangle.

This is an adaptation of the C++ code that impressed me by its simplicity.

API

Destructive

const a = [-10, -10],
  b = [10, 10];
clip(a, b, [-5, -5, 5, 5]); // returns 1 - "clipped"
console.log(a); // [-5, -5]
console.log(b); // [5, 5]

Non-destructive

const a = [-10, -10],
  b = [10, 10];
const an = a.slice(),
  bn = b.slice();
clip(a, b, [-5, -5, 5, 5], an, bn); // returns 1 - "clipped"
console.log(an); // [-5, -5]
console.log(bn); // [5, 5]
console.log(a); // [-10, -10]
console.log(b); // [10, 10]

Return value is 1 if the line was clipped, and 0 if it lies completely outside of the provided bounding box.

Install

npm install -S liang-barsky

import { clip } from 'liang-barsky';
// or
var clip = require('liang-barsky');

Or just drop-in the file

<script src="path/to/liang-barsky.umd.js"></script>
<script>
  liangBarsky.clip([0, 0], [10, 10], [0, 0, 5, 5]);
</script>

Performance

I ran a check against the Cohen-Sutherland algorithm implemented by @mourner for clipping just one segment. Though test include memory allocation, they are fair for the task at hand, since you can use the results in an equal manner after the invocation of the clipper.

npm run benchmark

liang-barsky x 112,058,856 ops/sec ±6.46% (87 runs sampled)
mapbox/lineclip x 27,754,592 ops/sec ±1.94% (98 runs sampled)
- Fastest is liang-barsky

Future plan

Implement a sub-routine for polylines. Loop through pairs, tracking in-out transitions.

License

MIT