Opportunistic tangible user interfaces for augmented reality.

Opportunistic Controls are a class of user interaction techniques that we have developed for augmented reality (AR) applications to support gesturing on, and receiving feedback from, otherwise unused affordances already present in the domain environment. By leveraging characteristics of these affordances to provide passive haptics that ease gesture input, Opportunistic Controls simplify gesture recognition, and provide tangible feedback to the user. In this approach, 3D widgets are tightly coupled with affordances to provide visual feedback and hints about the functionality of the control. For example, a set of buttons can be mapped to existing tactile features on domain objects. We describe examples of Opportunistic Controls that we have designed and implemented using optical marker tracking, combined with appearance-based gesture recognition. We present the results of two user studies. In the first, participants performed a simulated maintenance inspection of an aircraft engine using a set of virtual buttons implemented both as Opportunistic Controls and using simpler passive haptics. Opportunistic Controls allowed participants to complete their tasks significantly faster and were preferred over the baseline technique. In the second, participants proposed and demonstrated user interfaces incorporating Opportunistic Controls for two domains, allowing us to gain additional insights into how user interfaces featuring Opportunistic Controls might be designed.