Figure 1. A collection of interactive objects designed using our tool. All have electronic sensing or actuation components routed through their interior. Left: a radio, haptic feedback rabbit, maze, and presence-aware pen holder. Center: touch-sensitive toys. Right: custom neon signs. ABSTRACT3D printers offer extraordinary flexibility for prototyping the shape and mechanical function of objects. We investigate how 3D models can be modified to facilitate the creation of interactive objects offering dynamic input and output. We introduce a general technique to support rapidly prototyping interactivity by removing interior material from 3D models to form internal pipes. We describe the design space of pipes for interaction design, where variables include openings, path constraints, topologies, and inserted media. We then present PipeDream, a tool for routing internal pipes through 3D models, integrated within a 3D modeling program. We use two distinct routing algorithms. The first has users define pipes' terminals and uses path routing and physics-based simulation to minimize pipe bending energy, allowing easy insertion of media post-print. The second lets users supply a desired internal shape to which it fits a pipe route: for this we describe a graph-routing algorithm. We present prototypes created using our tool showing its flexibility and potential.

An increasing number of consumer products include user interfaces that rely on touch input. While digital fabrication techniques such as 3D printing make it easier to prototype the shape of custom devices, adding interactivity to such prototypes remains a challenge for many designers. We introduce Midas, a software and hardware toolkit to support the design, fabrication, and programming of flexible capacitive touch sensors for interactive objects. With Midas, designers first define the desired shape, layout, and type of touch sensitive areas, as well as routing obstacles, in a sensor editor. From this high-level specification, Midas automatically generates layout files with appropriate sensor pads and routed connections. These files are then used to fabricate sensors using digital fabrication processes, e.g., vinyl cutters and conductive ink printers. Using step-by-step assembly instructions generated by Midas, designers connect these sensors to the Midas microcontroller, which detects touch events. Once the prototype is assembled, designers can define interactivity for their sensors: Midas supports both record-and-replay actions for controlling existing local applications and WebSocket-based event output for controlling novel or remote applications. In a first-use study with three participants, users successfully prototyped media players. We also demonstrate how Midas can be used to create a number of touch-sensitive interfaces.

3D printers enable designers and makers to rapidly produce physical models of future products. Today these physical prototypes are mostly passive. Our research goal is to enable users to turn models produced on commodity 3D printers into interactive objects with a minimum of required assembly or instrumentation. We present Sauron, an embedded machine vision-based system for sensing human input on physical controls like buttons, sliders, and joysticks. With Sauron, designers attach a single camera with integrated ring light to a printed prototype. This camera observes the interior portions of input components to determine their state. In many prototypes, input components may be occluded or outside the viewing frustum of a single camera. We introduce algorithms that generate internal geometry and calculate mirror placements to redirect input motion into the visible camera area. To investigate the space of designs that can be built with Sauron along with its limitations, we built prototype devices, evaluated the suitability of existing models for vision sensing, and performed an informal study with three CAD users. While our approach imposes some constraints on device design, results suggest that it is expressive and accessible enough to enable constructing a useful variety of devices.

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