split-polygon

split-polygon

Splits a convex polygon by a plane into two parts (or optionally clips the polygon against a single plane) using the Sutherland-Hodgman algorithm. Works in arbitrary dimensions, both in the server and the browser

Install

npm install split-polygon

Example

var splitPolygon = require("split-polygon")

var poly = [[1,2], [3,4], [0,0]]

var parts = splitPolygon(poly, [0, 1, 3])

console.log(parts.positive)
console.log(parts.negative)

API

var splitPolygon = require("split-polygon")

splitPolygon(poly, plane)

Splits the convex polygon poly against plane into two parts, one above the plane and the other below it. The equation for the plane is determined by:

function planeDistance(x) {
  return plane[0] * x[0] + plane[1] * x[1] + ... + plane[n-1] * x[n-1] + plane[n]
}

Points above the plane are those where planeDistance(x) >= 0 and below are those with planeDistance(x) <= 0

• poly is a convex polygon
• plane is the plane

Returns An object with two properties:

• positive is the portion of the polygon above the plane
• negative is the portion of the polygon below the plane

splitPolygon.positive(poly, plane)

Same result as splitPolygon, except only returns the positive part. This saves a bit of memory if you only need one side.

splitPolygon.negative(poly, plane)

Ditto, except returns only the negative part.

Credits

(c) 2013 Mikola Lysenko. MIT License