...artists can stylize their curves while drawing by dynamically adjusting line thickness and color. Haptic effects enable artists to intuitively adjust line thickness by applying pressure against an imaginary 3D surface, making drawing in the air feel similar to pushing a paintbrush against paper. Artists can easily switch back and forth between the two variations, and can also edit their work with the system’s features.
http://www.physorg.com/news109425896.html
http://www-users.cs.umn.edu/~keefe/dfk_iweb/Home.html
http://www-users.cs.umn.edu/~keefe/dfk_iweb/Art.html