code: function Octahedron(r) {
    r = r || 0.5;
  
    var a = 1 / (2 * Math.sqrt(2));
    var b = 1 / 2;
  
    var s3 = Math.sqrt(3);
    var s6 = Math.sqrt(6);
  
    var vertices = [
      new Vec3(-a, 0, a), //front left
      new Vec3( a, 0, a), //front right
      new Vec3( a, 0,-a), //back right
      new Vec3(-a, 0,-a), //back left
      new Vec3( 0, b, 0), //top
      new Vec3( 0,-b, 0)  //bottom
    ];
  
    vertices = vertices.map(function(v) { return v.normalize().scale(r); })
  
    var faces = [
      [3, 0, 4],
      [2, 3, 4],
      [1, 2, 4],
      [0, 1, 4],
      [3, 2, 5],
      [0, 3, 5],
      [2, 1, 5],
      [1, 0, 5]
    ];
  
    var edges = [
      [0, 1],
      [1, 2],
      [2, 3],
      [3, 0],
      [0, 4],
      [1, 4],
      [2, 4],
      [3, 4],
      [0, 5],
      [1, 5],
      [2, 5],
      [3, 5]
    ];
  
    Geometry.call(this, { vertices: vertices, faces: faces, edges: edges });
  }
docs: ### Octahedron ( r ) `r` - radius *{ Number = 0.5 }*