In order to deform an object, our s

In order to deform an object, our system first puts an evenly spaced 2D grid of control points Gij on the object.
Then, the user sketches the first stroke (source stroke) upon (part of) the object. This represents the current state of the
object. Now a second stroke (deformation stroke) is drawn, which can be seen as a deformation of the source stroke.
Actually, this stroke indicates the desired deformation of the object.