Icosahedron.js

var geom = require('pex-geom');
var Vec3 = geom.Vec3;
var Geometry = geom.Geometry;

function Icosahedron(r) {
  r = r || 0.5;

  var phi = (1 + Math.sqrt(5)) / 2;
  var a = 1 / 2;
  var b = 1 / (2 * phi);

  var vertices = [
    new Vec3(  0,  b, -a),
    new Vec3(  b,  a,  0),
    new Vec3( -b,  a,  0),
    new Vec3(  0,  b,  a),
    new Vec3(  0, -b,  a),
    new Vec3( -a,  0,  b),
    new Vec3(  a,  0,  b),
    new Vec3(  0, -b, -a),
    new Vec3(  a,  0, -b),
    new Vec3( -a,  0, -b),
    new Vec3(  b, -a,  0),
    new Vec3( -b, -a,  0)
  ];

  vertices = vertices.map(function(v) { return v.normalize().scale(r); })

  var faces = [
    [  1,  0,  2 ],
    [  2,  3,  1 ],
    [  4,  3,  5 ],
    [  6,  3,  4 ],
    [  7,  0,  8 ],
    [  9,  0,  7 ],
    [ 10,  4, 11 ],
    [ 11,  7, 10 ],
    [  5,  2,  9 ],
    [  9, 11,  5 ],
    [  8,  1,  6 ],
    [  6, 10,  8 ],
    [  5,  3,  2 ],
    [  1,  3,  6 ],
    [  2,  0,  9 ],
    [  8,  0,  1 ],
    [  9,  7, 11 ],
    [ 10,  7,  8 ],
    [ 11,  4,  5 ],
    [  6,  4, 10 ]
  ];

  var edges = [
    [ 0,  1 ],
    [ 0,  2 ],
    [ 0,  7 ],
    [ 0,  8 ],
    [ 0,  9 ],
    [ 1,  2 ],
    [ 1,  3 ],
    [ 1,  6 ],
    [ 1,  8 ],
    [ 2,  3 ],
    [ 2,  5 ],
    [ 2,  9 ],
    [ 3,  4 ],
    [ 3,  5 ],
    [ 3,  6 ],
    [ 4,  5 ],
    [ 4,  6 ],
    [ 4, 10 ],
    [ 4, 11 ],
    [ 5,  9 ],
    [ 5, 11 ],
    [ 6,  8 ],
    [ 6, 10 ],
    [ 7,  8 ],
    [ 7,  9 ],
    [ 7, 10 ],
    [ 7, 11 ],
    [ 8, 10 ],
    [ 9, 11 ],
    [10, 11 ]
  ];

  Geometry.call(this, { vertices: vertices, faces: faces, edges: edges });
}

Icosahedron.prototype = Object.create(Geometry.prototype);

module.exports = Icosahedron;