3dm is a three dimensional (3D) surface modeling program that draws techniques of model manipulation from both CAD and drawing programs and applies them to modeling in an intuitive way. 3dm uses a head-mounted display (HMD) to simplify the problem of 3D model manipulation and understanding. A HMD places the user in the modeling space, making three dimensional relationships more understandable. As a result, 3dm is easy to learn how to use and encourages experimentation with model shapes.