  It is common to advise against using 3D to visualize abstract data such as
networks, however Ware and Mitchell's 2008 study showed that path tracing in a
network is less error prone in 3D than in 2D. It is unclear, however, if 3D
retains its advantage when the 2D presentation of a network is improved using
edge-routing, and when simple interaction techniques for exploring the network
are available. We address this with two studies of path tracing under new
conditions. The first study was preregistered, involved 34 users, and compared
2D and 3D layouts that the user could rotate and move in virtual reality with a
handheld controller. Error rates were lower in 3D than in 2D, despite the use
of edge-routing in 2D and the use of mouse-driven interactive highlighting of
edges. The second study involved 12 users and investigated data
physicalization, comparing 3D layouts in virtual reality versus physical 3D
printouts of networks augmented with a Microsoft HoloLens headset. No
difference was found in error rate, but users performed a variety of actions
with their fingers in the physical condition which can inform new interaction
techniques.
