Sketch-understanding systems let users interact with computers by drawing naturally, offering a freedom not available with traditional CAD systems.

"Magic Paper: Sketch-Understanding Research" by Randy Davis describes how sketch understanding systems let users draw more naturally and with a freedom not available with CAD systems so that they can create informal figures as a way of thinking or working through a problem.

Sketching is ubiquitous: We draw as a way of thinking, solving problems, and communicating in a wide variety of fields, for both design and analysis. Unfortunately in today’s technology, sketches are dead—they’re either graphite on slices of dead trees, or, if captured on a PDA or tablet computer, simply pixels of digitized ink. The Sketch Understanding Group at MIT has been working toward a kind of “magic paper”—that is, a surface that’s as natural and easy to draw on as paper, yet that understands what you draw.