In the previous chapter, which was on frame-based animation, we just covered 2D animation—essentially—giving the impression that one would not use such a technique for 3D meshes. Obviously, there is nothing keeping you from creating a series of meshes, which would form an animation when rendered in order. The obvious disadvantages of this would be the static nature of the animation and the inability to respond to environmental factors, including gravity. This is where skeletal animation offers many advantages.
Similarly, you can also use skeletal animations for 2D animations, and they offer many advantages. We somewhat touched on this in the discussion on tweening, and skeletal animation is, in some ways, a very evolved version of it. By employing skeletal animation, we can have many animations in our game without needing a significant amount of storage, and have the choice of adapting an animation to the environment and interpolating between animations.
A skeleton...