Morph target animation

In a morph target animation, a "deformed" version of a mesh is stored as a series of vertex positions.

[2] Typical examples of morph targets used in facial animation is a smiling mouth, a closed eye, and a raised eyebrow.

The interpolations between key poses when an animation is being rendered, are typically small and simple transformations of movement, rotation, and scale performed by the 3D software.

The artist has more control over the movements because they can define the individual positions of the vertices within a keyframe, rather than being constrained by skeletons.

In contrast, skeletal animation requires only the storage of bone transformations for each frame.

In this example from the open source project Sintel , four facial expressions have been defined as deformations of the face geometry. The mouth is then animated by morphing between these deformations. Dozens of similar controllers are used to animate the rest of the face.
An arbitrary object deformed by morphing between defined vertex positions.