Phil State

//  Util.js...
Object.type = function (_obj) {
  return Object.prototype.toString.call(_obj).slice(8, -1);
};
Object.set = function (_obj, _data, _keys) {
  var key, index, max, item, type;
  for (index = 0, max = _keys.length; index < max; ++index) {
    key = _keys[index];
    item = _data[key];
    type = Object.type(item);
    if (type === 'Object') {
      _obj[key] = Object.set({}, item);
    } else if (type === 'Array') {
      _obj[key] = item.slice();
    } else {
      _obj[key] = item;
    }
  }
  return _obj;
};

//  State.js...
var State = function (_data) {
  if (_data) { this.set(_data); }
};

State.prototype.set = function (_data) {
  if (Object.type(_data) === 'Object') {
    Object.set(this, _data, [
      'position',
      'momentum',
      'orientation',
      'angularMomentum',
      'velocity',
      'spin',
      'angularVelocity',
      'bodyToWorld',
      'worldToBody',
      'size',
      'mass',
      'inverseMass',
      'inertiaTensor',
      'inverseInertiaTensor'
    ]);
  }
};

State.prototype.recalculate = function () {
  // velocity
  vec3.multiply(this.momentum, this.inverseMass, this.velocity);
  // angularVelocity
  vec3.scale(this.angularMomentum, this.inverseInertiaTensor, this.angularVelocity);

  quat4.normalize(this.orientation);

  // spin
  quat4.multiply(quat4.create([this.angularVelocity[0], this.angularVelocity[1], this.angularVelocity[2], 0]),
  this.orientation,
  this.spin);
  var translation = mat4.create();

  mat4.translate(translation, this.position);
  mat4.multiply(translation, quat4.toMat4(this.orientation), this.bodyToWorld);
  mat4.inverse(this.bodyToWorld, this.worldToBody);
};