triangulate-contours/index.js

triangulates a series of 2D contours

var Tess2 = require('tess2')
var xtend = require('xtend')

module.exports = function(contours, opt) {
    opt = opt||{}
    contours = contours.filter(function(c) {
        return c.length>0
    })
    
    if (contours.length === 0) {
        return { 
            positions: [],
            cells: []
        }
    }

    if (typeof opt.vertexSize !== 'number')
        opt.vertexSize = contours[0][0].length

    //flatten for tess2.js
    contours = contours.map(function(c) {
        return c.reduce(function(a, b) {
            return a.concat(b)
        })
    })

    // Tesselate
    var res = Tess2.tesselate(xtend({
        contours: contours,
        windingRule: Tess2.WINDING_ODD,
        elementType: Tess2.POLYGONS,
        polySize: 3,
        vertexSize: 2
    }, opt))

    var positions = []
    for (var i=0; i<res.vertices.length; i+=opt.vertexSize) {
        var pos = res.vertices.slice(i, i+opt.vertexSize)
        positions.push(pos)
    }
    
    var cells = []
    for (i=0; i<res.elements.length; i+=3) {
        var a = res.elements[i],
            b = res.elements[i+1],
            c = res.elements[i+2]
        cells.push([a, b, c])
    }

    //return a simplicial complex
    return {
        positions: positions,
        cells: cells
    }
}