The third area of related work deals with creating 3-D models from 2-D sketches. Recently software has been developed that can construct a 3-D object from a 2D sketched drawing. For example, Teddy (Igarashi et al., 1997) models 3-D curved surfaces (such as a Teddy bear) from 2D freeform strokes. It creates a closed polygon from a stroke and finds a spine in center of the polygon. Next, it creates a 2D triangular mesh between the spine and the polygon perimeter, and then raises each spine vertex and smoothes the mesh. Digital Clay (Schweikardt and Gross, 2000) converts 2D.
