Computer graphics technology is used to create a virtual character in many applications such as movies and video games. The character motion is often created by capturing the actor's movement and edited to the virtual environment or another character of different body sizes. In this talk, we present our recent research of the motion adaptation method using a spacetime optimization technique. Our key idea is to represent the character motion as a spatiotemporal graph and deformit to satisfy some equality/inequality constraints while minimizing the least-square deformation error. Our system solves a cascaded series of quadratic programs, each layer of which comprises arbitrary types of constraints on graph node position, the spatiotemporal distance between the graph nodes, and the angle between the graph edges.