3D 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 that offer dynamic input and output. We
introduce a general technique for supporting the rapid prototyping
of interactivity by removing interior material from
3D models to form internal pipes. We describe this new 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 such
pipes through the interior of 3D models, integrated within
a 3D modeling program. We use two distinct routing algorithms.
The first has users to 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 allows users to supply a desired internal shape
to which we fit a pipe route: for this we developed a novel
graph-based routing algorithm. We present several prototypes
created using our tool to show its flexibility and potential.