one embodiment of the present invention sets forth a technique for providing an end user with a spatially - aware projector combined with a spatially - aware digital pen for use in a design environment . paper documents are augmented to allow a user to access additional information and computational tools through projected interfaces . virtual ink may be managed in single and multi - user environments to enhance collaboration and data management . the spatially - aware projector pen provides end - users with dynamic visual feedback and improved interaction capabilities .