code: function(array){
                  array = array || [];
                  var n = 0;
                  for(i=0; i<this.vertices.length; i++){
                      var v = this.vertices[i];
                      array[n++] = v.normal.x;
                      array[n++] = v.normal.y;
                      array[n++] = v.normal.z;
                  }
  
                  return array;
              }
docs: flatten each vertex normal once into an array, useful for OpenGL attributes
  @param {Array|Float32Array} [array] optionally pass in an array or typed-array to reuse
  @return {Array|Float32Array}