code: @Override
      public void setPosition(float x, float y, float z)
      {
          position.set(x, y, z);
          pickDir.set(x, y, z);
          pickDir.normalize();
          invalidate();
      }
docs: Set the position of the pick ray.
  This function is used internally to update the
  pick ray with the new controller position.
  @param x the x value of the position.
  @param y the y value of the position.
  @param z the z value of the position.