Not all animation DVDs follow the same method. The earliest and simplest method of animation uses sequences of 2D drawings. This method was used extensively in the earliest days of animation. Yet another method that does not require advanced computation is stop motion animation. But both of these methods have some serious limitations. These days most animations are achieved using computer software and virtual 3D models. Over the years, it has become cheaper to use computer software instead of hand drawing the sequences frame by frame.