translateOnAxis method
axis - A normalized vector in object space.
distance - The distance to translate.
Translate an object by distance along an axis in object space. The axis is assumed to be normalized.
Implementation
Object3D translateOnAxis(Vector3 axis, double distance) {
  // translate object by distance along axis in object space
  // axis is assumed to be normalized
  _v1.setFrom(axis);
  _v1.applyQuaternion(quaternion);
  _v1.scale(distance);
  position.add(_v1);
  return this;
}